THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 1 - JANUARY 97
In Brief: Some psychoactive drugs have actual performance-enhancing side effects. However, many actually decrease performance, primarily because of adverse cardiovascular effects and impaired judgment. Athletes and nonathletes alike may be knowingly or unknowingly exposed to psychoactive substances if they use over-the-counter, recreational, or prescription drugs. Many national and international sports federations ban or limit psychoactive drug use. The physiologic actions of psychoactive drugs and their use by high school and college athletes are discussed here.
Psychoactive drug use by high school and college athletes is extraordinarily common. A survey of Chicago area high school athletes (table 1) (1) revealed use of various over-the-counter and prescription medications as well as legal and illegal psychoactive drugs. Anabolic steroids, which have received considerable attention in the sports medicine literature, were used relatively infrequently. A more recent study of varsity-level college athletes in the Midwest showed similar results (2), in particular high utilization of smokeless tobacco; alcohol, including binge drinking; and marijuana. At least one study (3) showed that the use of alcohol by athletes was greater than that by sedentary college students.
| Table 1. Prevalence of Psychoactive Drug Use Among 1,117 Male High School Athletes in the Chicago Area | |
| Drug | Percent Using |
| Beer | 67.6 |
| OTC drugs | 56.7 |
| Wine/whiskey | 54.5 |
| Oral smokeless tobacco | 32 |
| Cigarettes | 27.9 |
| Caffeine | 27.1 |
| Marijuana | 18.5 |
| Narcotics | 9.9 |
| Hallucinogens | 9.2 |
| Inhalants | 4.9 |
| Amphetamines | 3.8 |
| Cocaine | 2.4 |
| Anabolic steroids | 2.2 |
| Adapted from Forman et al (1). | |
Primary care physicians must consider the potential for psychoactive drug use by their young patients, athletes or not. The properties and physiologic effects, particularly as related to athletic performance, of a wide range of psychoactive drugs are discussed here. In addition, the current policies of the National Collegiate Athletic Association (NCAA) and the International Olympic Committee (IOC) regarding these drugs are summarized.
Alpha-adrenergic agents. These drugs are constituents of many over-the-counter medications, some of which are used for weight loss (phenylpropanolamine hydrochloride) and to treat asthma and upper respiratory infections (ephedrine, phenylephrine, and epinephrine). Their primary effect is autonomic cardiac stimulation as well as an amphetamine-like central nervous system (CNS) stimulation that results from their displacement of norepinephrine and other brain monoamines. Possible side effects at commonly used dosages include tachycardia, headache, dizziness, hypertension, anorexia (hence their use by athletes in appearance sports), irritability, anxiety, mania, and, at high doses, psychosis.
Some research (4,5) has demonstrated no effect of alpha-adrenergic agents on strength, endurance, reaction time, anaerobic capacity, or recovery time after prolonged exercise. All systemic use has been banned by the IOC, but topical use is permitted (eg, oxymetazoline hydrochloride and phenylephrine nasal spray).
Ma huang is an herbal form of ephedrine called ephedra that is contained in many herbal products available in health food stores, often in conjunction with chromium. Recent changes in US Food and Drug Administration (FDA) regulations excuse the makers of nutrition supplements from fully identifying the contents of their products. Ma huang has been blamed for the deaths of several high school students who used it as a stimulant or aphrodisiac; the deaths presumably resulted from CNS bleeding or cardiac arrhythmia. Its use is banned by the IOC (6).
Caffeine. This substance has been used as stimulant since the Stone Age. Its concentration ranges from 4 mg per cup in decaffeinated coffee to 220 mg in coffee prepared by the drip method. Concentrations range from 60 to 150 mg in most colas and coffee. The average consumption in the United States is 206 mg per day; 10% of the adult population consumes more than 1,000 mg per day (7). Caffeine is chemically related to the methylxanthines and inhibits the action of cyclic nucleotide phosphodiesterase, leading to increased cyclic adenosine monophosphate (cAMP) levels. A dose of 80 to 200 mg leads to increased alertness, shortened reaction time, and improved concentration, but the response varies greatly among individuals. At doses over 250 mg (2 to 3 cups of coffee), the nonhabitual user usually experiences a headache and nervousness, which is the definition of caffeinism proposed by the American Psychiatric Association (8). For habitual users, abstinence for as little as 24 hours leads to a withdrawal syndrome of headache, irritability, insomnia, and dysphoria.
The physiologic effects of caffeine include diuresis, gastric acid release, smooth muscle relaxation, increased contractility of skeletal muscle, increased lipolysis, and increased heart rate, blood pressure, oxygen consumption, and metabolic rate. Moderate exercise leads to increased peak plasma concentrations, which explains the experience of many recreational runners who find an additional stimulant effect from the usual consumption of coffee following a morning run. Urinary clearance of caffeine is slowed by oral contraceptives and alcohol.
The effect of caffeine on short-duration, high-intensity performance is negligible at levels under the IOC limit, with animal studies showing an effect only at concentrations 10 times or more that allowed in humans. Caffeine has been shown to increase exercise time during graded incremental performance, but the practical significance of this finding is unclear because of the high dosages used (9). However, during prolonged endurance exercise, the benefits of caffeine are more clear. Studies (7,9) have shown a 7% increase in work output and a 19% increase in exercise time with caffeine use; the proposed explanation is that caffeine enhances lipolysis and free fatty acid release, which would spare muscle glycogen use. Another suggested explanation for caffeine's enhancement of endurance exercise is CNS stimulation, perhaps through catecholamine release.
The only consistent benefit of caffeine is in submaximal, prolonged endurance exercise, but there is controversy as to whether this benefit is realized at the concentrations allowed by the IOC (maximum urinary concentration of 12 micrograms/mL, equal to 8 cups of coffee in 2 to 3 hours) and the NCAA (maximum urinary concentration of 15 micrograms/mL) (6). Some athletes have approached or exceeded the IOC threshold despite seemingly minimal caffeine intake, and athletes should be advised of this possibility. Caffeine is the only substance for which the IOC has set a urinary threshold.
Nicotine. Exposure to nicotine occurs with both cigarette smoking and smokeless tobacco use. The toxicity of tobacco smoke, with its approximately 4,000 chemical constituents, is well known. Because of its immediate cardiorespiratory toxicity, fewer athletes than nonathletes smoke tobacco (1,2), although the prevalence is not as low as one might expect. A fact that can be useful in educating athletes about the hazards of tobacco smoke is that carbon monoxide is a prominent ingredient and that its high affinity for hemoglobin, 200 to 300 times that of oxygen, produces carboxyhemoglobin levels of 5% to 10%, depending on the number of cigarettes smoked per day. These levels are in the lower range of those that might cause mild lethargy as a result of carbon monoxide poisoning from defective natural gas furnaces (10).
Smokeless tobacco is used by 20% to 60% of male college athletes (use varies among sports and is highest in baseball) and 5% to 10% of female college athletes (highest in softball) (1,2). The CNS stimulation and skeletal muscle relaxation produced by nicotine cause athletes to underestimate muscle tension related to athletic performance but do not decrease the rating of perceived exertion (7). Reaction time is not affected. Vasoconstriction leads to an increased heart rate and blood pressure and a decreased stroke volume (by as much as 30% to 40%) (7,8). Nicotine yields no proved benefit in any athletic endeavor, and hence it is not banned by the IOC or NCAA. However, the NCAA has mounted an intense antitobacco campaign and has set regulations regarding use during competition.
Melatonin. This substance is marketed as a "natural" sleep agent and is available in dosages of 1 to 3 mg. At this level, its purported benefits are shortened sleep onset and decreased time to stage 2 sleep without a "hangover" the next morning. Anecdotal reports suggest widespread use by athletes, especially when traveling, but controlled studies of its effects are sparse (11). Interestingly, the usual nocturnal increase in melatonin is greater in amenorrheic than in eumenorrheic athletes, suggesting that melatonin may play a role in exercise-associated menstrual disturbances (12).
Alcohol. Alcohol blocks the release of acetylcholine, resulting in decreased serotonin turnover and increased noradrenergic activity. The result of these neurotransmitter alterations is euphoria followed by depression (8). Alcohol has long been used as a prerace stimulant (sometimes laced with strychnine), and its prominence in sports promotion and marketing is obvious. College athletes express more negative attitudes about alcohol use than nonathletes do, but this may reflect only socially acceptable responses on questionnaires, since they show the same drinking behaviors, particularly binge drinking, as nonathletes (13).
Controlled studies of alcohol's effect on athletic performance are difficult to blind because of the easily recognizable taste of alcoholic beverages (7). To blind participants to the presence of alcohol, most researchers use vodka, at an insignificant concentration but sufficient for taste, or noseclips and anesthetic throat lozenges. Limited evidence suggests increased isometric muscle strength at low doses of alcohol because of CNS disinhibition of neuromuscular impulses. Other significant effects include impaired gluconeogenesis, lowered resting muscle glycogen levels, poor temperature regulation, diuresis, and direct cardiotoxicity, all of which impair athletic performance. For unclear reasons, alcohol produces an increase in VO2 at submaximal exercise intensity but has no effect on VO2 max, resulting in decreased exercise time to exhaustion and decreased performance in middle-distance running events (7,14).
Athletes engaged in activities that require precise fine motor control, such as archery and shooting, have a perception of reduced tension and increased relaxation as a result of alcohol, but the actual effect is decreased hand-eye coordination and impaired judgment and tracking; this results in a less smooth release in archery, increased reaction time, and confusion. Alcohol is banned by the NCAA for riflery and by the international federations that govern the modern pentathlon, fencing, and shooting.
Marijuana. This drug is tried by at least a third of high school students and may be used more commonly than cigarettes because it is incorrectly perceived to contain fewer toxic irritants and ergolytic chemicals than tobacco smoke (14,15). Tetrahydrocannabinol (THC), the active ingredient, causes sedation and euphoria at low doses and hallucinations and psychosis at high doses. Its effects on athletic performance are increased reaction time, decreased fine-motor coordination, and increased heart rate. These effects, along with the vasodilating effect, cause an athlete to reach maximal heart rate at a lower than normal intensity of exercise, resulting in a decreased maximal work capacity. Chronic marijuana use has been associated with decreased motivation to perform and to give a maximal effort as well as with decreased circulating testosterone levels (8); this second effect may be persuasive when counseling teenage male athletes against marijuana use. Marijuana use is illegal and is banned by the NCAA. National and international sports federations test athletes for marijuana use on a discretionary basis.
Cocaine. This stimulant was isolated in the mid-1800s. Although soldiers in the late 1800s used it to decrease fatigue, its current use is primarily recreational. An estimated 3 million persons in the United States were cocaine users in 1991. Its basic pharmacologic effect is an increased synaptic concentration of dopamine, and its use is reinforced and mediated through dopamine pleasure receptors (8). Cocaine is more addictive than amphetamine, and withdrawal produces fatigue, lack of motivation, and depression. Positron-emission tomography studies of cocaine users have demonstrated decreased glucose metabolism in the cerebral cortex and temporal lobe during cocaine use and rebound increases to above-normal levels upon withdrawal (14,15).
Cocaine is notable for distorting the user's perception of reality; for example, an athlete may perceive increased performance and decreased fatigue in the face of actual decreased performance in both strength and endurance activities. Cocaine produces a catecholamine-induced as well as a direct negative effect on glycogenolysis, which affects athletic performance. Its more important adverse effects include paranoid psychosis, seizures, hypertension-related CNS bleeding in the presence of vascular malformations, coronary artery vasoconstriction and myocardial toxicity leading to arrhythmias and ischemia, and sudden death (14,15). Cocaine use, including its use as a local anesthetic, is banned by both the NCAA and the IOC.
Methylenedioxymethamphetamine (ecstasy, MDMA, XTC). MDMA results from substitutions on the aromatic nucleus of amphetamine, which diminish the agent's stimulant effects and increase its hallucinogenic effects (7,8) It is closely related to 2,3- and 3,4-methylenedioxyamphetamine (MDA), also known as the "love drug," hence the common phrase "to have sex with X[TC]." Whether it offers any benefits as a stimulant in sports is unknown. Recreational use may be revealed by amphetamine drug testing.
Anabolic steroids. The metabolic and hormonal effects of anabolic steroids will not be addressed here, but there are significant psychological effects that deserve brief mention. While lacking controlled studies, the literature is full of case reports and case series describing depression, suicidal ideation, psychosis, delirium, mania, aggression, and homicidal behavior as a consequence of anabolic steroid use. The mechanisms of these effects are unclear, but probably involve neurotransmitter receptor systems in such areas as the amygdala (16).
Benzodiazepines. The first benzodiazepine (BZD), chlordiazepoxide hydrochloride, was patented in 1959 and the second, diazepam, in 1963. Today at least 39 BZDs are available for prescription. These drugs block the release of acetylcholine (much as alcohol does) and decrease the turnover of norepinephrine, particularly during periods of stress, producing sedative, hypnotic, anticonvulsant, and muscle relaxant effects (8). The primary anxiolytic effect is mediated through gamma-aminobutyric acid (GABA). BZDs and GABA enhance each other's binding to GABA receptors, resulting in a decreased release of serotonin. The muscle relaxation effects are mediated at the spinal cord level, but other effects are mediated at the cerebral cortex. BZDs are often used to relax muscles following an injury, such as a lumbosacral strain, but there is no evidence that they have an effect on specific muscles, only a CNS-mediated relaxation effect. BZDs alter sleep by increasing total time asleep, reducing sleep latency, and decreasing total time in rapid-eye-movement (REM) sleep; however, the number of REM cycles is increased, resulting in more dreams. Conversely, BZD withdrawal often results in nightmares or bizarre dreams.
The half-life of all BZDs and their metabolites is 6 to 20 hours or more. (This includes flurazepam hydrochloride, which is metabolized to the active metabolite N-desalkylflurazepam and is often suggested, incorrectly, to have short-acting, no-hangover properties.) BZDs are sometimes used by athletes as a sleep aid, particularly during travel to competitions to prevent jet lag, but the predictable morning-after hangover results in a prolonged reaction time and dulled senses (4). These drugs have been promoted by athletes and coaches as a substitute for alcohol in shooting (in the modern pentathlon and biathlon). Their use is banned by some sports federations and by the US Olympic Committee (USOC), although not specifically by the IOC. Their use is absolutely contraindicated for underwater divers.
Gamma-aminobutyric acid (GABA). This substance is widely available in natural food and health catalogs and is rumored to be used for its anxiolytic effect, but little more is known because of inadequate testing methods. GABA receptors are a major mediator of anxiety and depressive disorders and are functionally associated with BZD binding sites, as noted above. BZD binding is enhanced by GABA such that there is a functional, although not an anatomical, relationship between BZD and GABA receptors (8). Plasma and cortical GABA levels are low in intractable depression, but the effects of exogenous GABA are unknown.
Narcotics. Narcotics are used primarily to relieve pain and to enable an athlete to compete despite painful injuries. They have no ergogenic effect on exercise tolerance or VO2 max. Narcotics that are banned, including morphine and meperidine, are banned because they impair judgment and hence the ability to perceive dangerous situations (14,15). Codeine, dihydrocodeine bitartrate, and dextromethorphan hydrobromide are not currently banned by the USOC (codeine was a banned substance until 1994) (6). Narcotic analgesics (other than heroin) are not banned by the NCAA, but since one of the metabolites of codeine is morphine, a positive drug test is possible. The recent highly publicized treatment of pro football quarterback Brett Favre for hydrocodone bitartrate addiction and reports of the ready availability of unlimited quantities of addictive narcotics in team locker rooms and training facilities suggest the extent to which these drugs have become a part of athletic culture.
Beta-adrenergic agents. Clenbuterol is the most notorious of the beta-adrenergic agents, which have been found to have anabolic properties. Several studies of laboratory animals and livestock have demonstrated marked increases (13% to 65%) in muscle mass with clenbuterol as well as with several other long-acting beta-agonists (7). These anabolic effects are not mediated through testosterone, growth hormone, or insulin. Beta-adrenergic agents are illicitly used to maintain anabolic effects after steroid use is discontinued; their potency is approximately 25% of that of anabolic steroids. They also enhance lipid metabolism, increase lipolysis, decrease fat deposition, and increase lean body mass and the lean-to-fat ratio.
Clenbuterol has the longest half-life of all the commonly available beta-agonists (35 hours, compared with 5 hours for albuterol sulfate) and is considered to be the most potent by athletes (7). A long half-life may be necessary to produce an anabolic effect, but human studies have shown a 14% to 18% increase in hamstring and quadriceps muscle strength at oral albuterol dosages of 8 mg twice a day (a dose at which most humans have significant side effects). Side effects of clenbuterol are the expected ones for a beta-agonist: tachycardia, palpitations, muscle tension, headache, and dizziness.
Beta-adrenergic agents are most commonly used therapeutically in inhaled form to treat asthma. Approximately 10% to 15% of athletes at most levels of competition have exercise-induced bronchospasm, and an additional few have more severe inflammatory forms of asthma. The use of all beta-adrenergic agents in inhaled form was permitted by the IOC until 1992, when the anabolic properties of these drugs were quantified. At that time, all long-acting inhaled and oral forms, including clenbuterol (available only in Europe and for veterinary use) and salmeterol xinafoate, were banned by the IOC and were classified as "stimulants" and "other anabolic agents." Inhaled albuterol and terbutaline sulfate are permitted by the IOC after approval subject to verified medical indication. Use of salmeterol in inhaled form also is now permitted by the IOC, since studies have demonstrated a negligible anabolic effect (6,17). Clenbuterol was banned by the NCAA in 1993 as an "anabolic steroid," but all other long-acting beta-adrenergic agents are permitted by the NCAA in inhaled form; oral forms are banned as "stimulants." The NCAA allows the use of theophylline and cromolyn.
Beta-adrenergic antagonists (beta-blockers). Beta-blockers are commonly used to treat hypertension, angina, arrhythmias, migraine headache, and anxiety and are frequently given after myocardial infarction. Their central anxiolytic effect occurs in direct proportion to their lipophilic binding, but their propensity to cross the blood-brain barrier also contributes to CNS-mediated side effects such as nightmares, depression, insomnia, and fatigue (8).
Beta-blockers have no effect on strength or power, but they reduce available energy by decreasing insulin release, glycogenolysis, and lipolysis. Their inotropic and chronotropic effects, ie, decreased heart rate, stroke volume, cardiac output, and VO2 max, are undesirable for endurance athletes. Beta-blockers can markedly reduce catecholamine-mediated palpitations, tremor, flushing, and diarrhea (13,15). Metoprolol tartrate use has been associated with a 13% improvement in shooting, the greatest effect being observed for the best shooters (3). Beta-blockers were originally banned by the IOC in 1985, but this restriction was subsequently eased and now affects only those sports for which enhanced performance is likely, including archery, shooting (the only sport listed by the NCAA), fencing, equestrian events, biathlon and modern pentathlon (because of the shooting event), bobsled, luge, diving, synchronized swimming, and ski-jumping.
Beta-blockers are commonly used to reduce performance anxiety in musicians, teachers, and business executives, although reports are mostly anecdotal, with a recommendation for a short-acting, low-dose preparation, such as propranolol hydrochloride 10 to 20 mg. In a double-blind, controlled crossover comparison of 40 mg nadolol and 2 mg diazepam, the measured psychological anxiety was the same with both medications, but technical performance was better with nadolol due to an attenuation of the expected increase in heart rate and tremor. Diazepam resulted in a deterioration of performance (18).
Methylphenidate hydrochloride and related amphetamines. Methylphenidate hydrochloride is one of several structurally related amphetamines; its increased use in the treatment of patients who have attention deficit hyperactivity disorder (ADHD) has made it the amphetamine that most physicians encounter most often.
Amphetamine was synthesized in 1920 and was initially used as a nasal decongestant. It was commonly used to reduce fatigue and to increase alertness in soldiers during World War II. Amphetamine use has been shown to increase the speed of learning new tasks and to increase physical energy, confidence, and ambition on a short-term basis. At least four mechanisms of action have been proposed: enhanced release and reduced re-uptake of dopamine, norepinephrine, or serotonin, leading to enhanced neurotransmitter agonist activity; and monoamine oxidase inhibition (8). Amphetamines are highly addictive, particularly when absorbed through mucosal surfaces. High school students are known to use sublingual absorption to enhance the stimulant effect of methylphenidate.
Amphetamines are not known to enhance athletic performance, but enhanced confidence and aggression (possibly on a placebo basis) may lead to a 1% to 2% increase in short-term power activities. At elite levels of competition, such an improvement may be significant. Athletes who use amphetamines may be able to tolerate a longer period of anaerobic metabolism, although credible data on this effect are not available.
Of greatest importance are the serious, and sometimes fatal, side effects of amphetamine use, such as heatstroke due to shunting of blood away from the skin. A more common problem is impaired judgment, which may cause the athlete to participate while injured, possibly leading to worse injuries and putting others at risk. Amphetamines are banned by both the IOC and the NCAA, although the NCAA does permit the use of methylphenidate for ADHD if this need is documented. The practical implementation of this exception has yet to be fully assessed because of the imprecision of ADHD diagnosis and the theoretical possibility that methylphenidate prescribed for legitimate purposes may be used inappropriately.
Tricyclic antidepressants (TCAs). Imipramine, the first TCA, was developed for the treatment of psychotic agitation (8). All TCAs inhibit the neuronal uptake of norepinephrine and serotonin to various degrees. These drugs are most effective in the treatment of severe, melancholic, major depressive disorder, particularly with psychomotor agitation (because of its neuroleptic origins) and postpsychotic depression. They are also effective for obsessive-compulsive disorder (eg, clomipramine hydrochloride), panic disorder, generalized anxiety disorder, and posttraumatic stress disorder.
Most TCAs (particularly amitriptyline hydrochloride) produce numerous side effects relating to multiple receptor systems; each drug in the class causes various degrees of antihistaminic, antimuscarinic, alpha-adrenergic-antagonistic, and anticholinergic effects. Tricyclic antidepressants reduce cardiac capacity and increase the risk of arrhythmias as a result of quinidine-like effects, such as QT prolongation. Some studies have demonstrated increased running or swimming time to exhaustion in rats given imipramine hydrochloride or desipramine hydrochloride. The side effects of TCAs, particularly cardiac conduction abnormalities, preclude their use by athletes with clinical depression. These drugs are banned by the IOC only for athletes in shooting events (including the modern pentathlon and biathlon) because of their anxiolytic effects.
Fenfluramine hydrochloride. This is a serotonergic agent recently approved for the long-term treatment of obesity. It is chemically related to amphetamines but has a minimal stimulant effect and a low potential for abuse. This drug appeals to athletes such as gymnasts, wrestlers, and rowers because of its anorexigenic effect. Fenfluramine is not currently banned by any athletic organization or federation.
Selective serotonin reuptake inhibitors (SSRIs). An SSRI is the first-line medication used to treat most patients with depression in the United States. Fluoxetine hydrochloride, with over $2 billion in annual sales, is the most frequently prescribed antidepressant (19). This class of psychiatric drug was the first designed with specific predetermined criteria in mind. SSRIs have a nearly exclusive effect on neuronal uptake of serotonin and minimal to no effect on the receptor systems affected by TCAs.
SSRIs produce numerous but relatively minor side effects, including nausea, headache, diarrhea, dyspepsia, agitation, and tremulousness. Sexual dysfunction is the most troublesome side effect for many patients. The relative lack of serious side effects makes an SSRI a better choice than a TCA for the treatment of clinical depression in athletes. These drugs can produce ergogenic effects, including prolonged running time to exhaustion, decreased central fatigue, and enhanced motivation and self-esteem, which may improve training and performance (20,21) These drugs are banned by the IOC for shooting sports (including modern pentathlon and biathlon) because of their anxiolytic effects.
Psychoactive drug use among young athletes often results from these drugs' perceived, and sometimes actual, enhancement of performance. The use of many psychoactive drugs is regulated or banned by national and international sports federations, which does provide a deterrent effect. Primary care physicians must be mindful of both deliberate and unintentional psychoactive drug use among their young athletic patients and the potential for serious or life-threatening complications related to this use.
Dr Schwenk is professor and chair in the Department of Family Practice at the University of Michigan Medical School in Ann Arbor. He is a fellow of the American College of Sports Medicine. Address correspondence to Thomas L. Schwenk, MD, Department of Family Practice, University of Michigan Medical Center, 1018 Fuller St, Ann Arbor, MI 48109.
THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 11 - NOVEMBER 97
Waking up to a steaming mug of coffee, enjoying an iced tea with lunch, and drinking a cold cola for an afternoon pick-me-up are daily pleasures enjoyed worldwide. And because the mild stimulant effect of caffeine lasts only a few hours, people in need of a lift often seek out serving after serving of these caffeinated beverages.
Caffeine, however, has been condemned by "clean living" advocates because it has no nutritional value, is not needed for any physiologic function, and is commonly abused by the tired and stressed. As a result, many coffee drinkers worry that their early morning mugful will contribute to health problems. The truth is, coffee and other caffeinated beverages in moderation are not health demons.
Caffeine is one of the best-researched substances in the food supply. The overwhelming scientific evidence suggests that, in moderation, it has no adverse health effects. According to the International Food Information Council, moderation means 1 to 2 mugs (10 to 20 ounces) of brewed coffee per day, or 3 to 6 12-ounce glasses of iced tea (table 1: not shown).
While little harm can be directly associated with coffee or other caffeinated beverages, coffee drinkers do tend to do things that contribute to health risks. Surveys suggest that they are more likely to smoke cigarettes, exercise too little, and eat fatty meats. Tea drinkers, in comparison, tend to exercise more and eat more fresh fruit.
For women, caffeine has been suspected as a factor in fibrocystic breast disease. But no research supports the connection, and the American Medical Association has stated that there is no association between caffeine intake and fibrocystic breast disease, benign tumors, breast tenderness, or breast cancer--or cancer of any type. Also, caffeine is not an important risk factor for osteoporosis in women who drink at least one glass of milk per day. But when caffeinated beverages replace milk, low calcium intakes may interfere with bone health.
A woman who wants to start a family should be aware that consuming over 300 milligrams of caffeine a day might increase the time it takes to get pregnant, as well as the risk of miscarriage or a low-birth-weight baby. The US Food and Drug Administration recommends that pregnant women avoid caffeine-containing foods and drugs or consume them only sparingly, because caffeine crosses the placenta and is a stimulant to the unborn baby. It is also transferred into breast milk, so women who breastfeed should avoid caffeine.
If you are prone to anemia, note that polyphenols in coffee and tea can interfere with iron absorption. Your best bet is to drink caffeinated beverages an hour before a meal, rather than afterward.
Some people become dependent on caffeine, experiencing withdrawal symptoms such as headaches, fatigue, or drowsiness if they abstain. These effects last only a few days and can be avoided by gradually reducing caffeine intake instead of quitting "cold turkey."
Because caffeine enhances performance in many individuals, it has been banned by the International Olympic Committee. But ironically, the level at which caffeine is banned far exceeds the amount needed to enhance performance. Higher, illegal levels are generally attained with caffeine supplements, since a 150-pound athlete would need to drink 3 to 4 large cups of coffee within an hour before activity to reach the upper acceptable limit. Just 1.5 to 3 milligrams of caffeine per pound of body weight (225 to 450 milligrams for a 150-pound man) is enough for an energy-enhancing effect. That's as little as one 10-ounce cup of coffee!
Habitual caffeine consumers experience less ergogenic effect than people who consume it rarely. For the optimal ergogenic benefit, the trick may be to use caffeine strategically at certain points to allow for harder training, and then discontinue it to avoid developing a tolerance.
Caffeine affects each person's performance differently. Some athletes thrive on it; others prefer to abstain because it causes stomach upset, nervousness, or jitters. Clearly, if caffeine makes you queasy or lightheaded during exercise, don't use it!
Caffeine also has a diuretic effect--that is, it enhances urine formation, often causing a need to urinate within an hour after consumption. Yet two studies with subjects who took caffeine before they exercised (1,2) showed no detrimental effects on hydration during exercise. Thus it appears that caffeine does not increase urine production during exercise. The extra adrenaline your body secretes during exercise may block caffeine's effect on the kidneys (3). However, responses to caffeine vary, so you should base your preexercise consumption on how caffeine affects your body.
After exercise, caffeine is a poor choice for fluid replacement. The safest bet is to tank up on noncaffeineated beverages just after activity, and then later, if you so desire, enjoy your favorite caffeinated beverage in moderation.
Remember: You, your physician, and your nutritionist need to work together to discuss nutrition concerns. The above information is not intended as a substitute for appropriate medical treatment.
Ms Clark is director of Nutrition Services at SportsMedicine Brookline in the Boston area. She is a fellow of the American College of Sports Medicine, a fellow of the American Dietetic Association, and a member of its practice group, Sports and Cardiovascular Nutritionists (SCAN).
THE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 4 - APRIL 96
Once upon a time, the "best" sports diets were based on steak and eggs. Supposedly, meat-eating athletes were stronger, more muscular, and more aggressive. Today, we know that strength and muscles are built with exercise (not extra protein), and that carbohydrates provide the fuel needed for muscle-building exercise.
But in the transition from a high-protein to high-carb diet, many athletes have eliminated meat--and have also overlooked the importance of protein. Some have taken the public health recommendations to eat less saturated fat to the extreme and are surviving on fat-free bagels and pasta. This type of diet may seem ideal, but in addition to being low in protein, it lacks important nutrients such as iron (needed to carry oxygen to working muscles) and zinc (needed for healing).
Many of these so-called "vegetarian" athletes are simply non-meat eaters who have not bothered to replace meat protein with plant proteins. They may think they are gaining a competitive edge, but they are actually hindering themselves. They often have lingering colds, nagging injuries, poor recovery from workouts, and overall fatigue as dietary imbalances take their toll.
Protein has recently reentered the spotlight. Some sports nutrition gurus advocate getting as much as 30% of daily calories from protein, double the standard 12% to 15% recommendation. Confused? Join the club. Here are some protein questions and answers that should help.
Protein is made up of chains of amino acids, some of which our bodies cannot manufacture. Protein is essential for building and maintaining muscles, as well as repairing the muscle damage that occurs during training. Protein is also needed to make red blood cells, produce hormones, boost your immune (disease-fighting) system, and help keep hair, fingernails, and skin healthy. Athletes who are protein deficient may complain about having hair that falls out easily and fingernails that grow slowly and break easily. Female athletes who eat a protein-poor diet may also stop having periods (1).
There isn't an exact number for athletes because protein needs vary, depending on whether an athlete is growing, rapidly building new muscle, doing endurance exercise, or dieting, in which case protein is used as a source of energy (table 1). Protein requirements for athletes are higher than the current recommended dietary allowance (RDA) of 0.4 g of protein per pound of body weight, which is based on the needs of nonexercisers. Protein recommendations for athletes are commonly expressed in a range to include a safety margin (2). If you do the math (1g of protein has 4 calories), you'll see that you don't need to have 30% of your calories come from protein.
| Table 1. Recommended Grams of Protein Per Pound of Body Weight Per Day* |
|
| RDA for sedentary adult | 0.4 |
| Adult recreational exerciser | 0.5-0.75 |
| Adult competitive athlete | 0.6-0.9 |
| Adult building muscle mass | 0.7-0.9 |
| Dieting athlete | 0.7-1.0 |
| Growing teenage athlete | 0.9-1.0 |
| *To find your daily protein requirement, multiply the appropriate numbers in this table by your weight in pounds. | |
No. Per pound of body weight, bodybuilders actually need less protein than endurance athletes such as runners. That's because protein--or more precisely, the amino acids that are the building-blocks of protein--is actually used for fuel during intense exercise, particularly when carbohydrates are not available. Protein can provide up to 10% of energy during exercise when a person is carbohydrate depleted (3).
But here's the catch: Even though endurance athletes may need more protein per pound of body weight, they tend to need a smaller total intake of protein because they often weigh less than bodybuilders. For example, a 200-pound bodybuilder may need about 140 g of protein a day (0.7 g of protein per pound), whereas a 150-pound marathoner may need about 120 g of protein per day (0.8 g of protein per pound). Most people can get enough protein through their diet, eliminating the need for protein supplements.
Lean cuts of red meats are not bad for athletes. The best choices include flank steak, London broil, eye of the round, and extra-lean ground beef. Besides being protein-rich (table 2: not shown), lean red meat is an excellent source of iron and zinc.
Some athletes are afraid of the cholesterol in red meats. But actually the cholesterol content of red meat is similar to that of chicken and fish. Yes, fatty hamburgers, pepperoni, bacon, and ribs are unhealthy and should be eaten only occasionally, if at all. But athletes can healthfully have about 4 oz of lean meat two to four times per week. In fact, a lean roast beef sandwich could be a healthier choice for the heart than a veggie sandwich packed with cheese.
Yes. Vegetarian athletes can eat enough protein to satisfy their bodies' needs if they wisely choose plant proteins. Lacto-ovo vegetarians (who eat eggs, milk, yogurt, cheese, and other dairy foods but no meat) can most easily consume adequate protein because these foods are excellent sources of life-sustaining protein and contain all the essential amino acids.
The key for total vegetarians, or vegans (who eat no milk, eggs or other animal proteins), is to eat a variety of grains that have complementary amino acids. For example, beans and rice is an example of mixing legumes (peas and beans) and grains. Also, tofu is an excellent addition to a vegetarian diet. Tofu has made headlines because it is a high-quality plant protein that contains all essential amino acids and offers the bonus of phytochemicals that protect against heart disease (4) and cancer (5).
A word of caution: Although vegetarian athletes can consume adequate protein from their diet, they have to be willing to eat large amounts of plant proteins. This is often easier for men with hearty appetites than for weight-conscious women. If you are eating a vegetarian diet that consists primarily of grains, fruits, and vegetables, you are probably eating an unbalanced diet. You might want to consult with a sports nutritionist who can help you add the right amount of protein. For a referral to a local sports nutritionist, call the American Dietetic Association's referral network at 1-800-366-1655.
Remember: You, your physician, and your nutritionist need to work together to discuss nutrition concerns. The above information is not intended as a substitute for appropriate medical treatment.
Ms. Clark is director of Nutrition Services at SportsMedicine Brookline in the Boston area. She is a fellow of the American College of Sports Medicine, a fellow of the American Dietetic Association, and a member of its practice group, Sports and Cardiovascular Nutritionists (SCAN).
THE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 10 - OCTOBER 96
With as many sports nutrition ideas as choices in a supermarket, it's no wonder people become perplexed. Sometimes the results from a new study on food can completely contradict what you may have previously heard, leaving you more confused than ever. To help you out, here are some basic questions that I am routinely asked--and their straightforward answers.
1. What's the right balance of carbohydrate, protein, and fat?
If you eat too many carbohydrates, you may deprive your body of protein and fat. The best balance for a sports diet is 60% to 65% of the calories from carbohydrates, 10% to 15% from protein, and 20% to 30% from fat. This means that meals are based on carbohydrates, not made up exclusively of carbohydrates.
Your protein intake should be two small servings per day to build and protect muscles. A few examples of a serving would be 2 tablespoons of peanut butter, 3 ounces of chicken, or 1/2 cup of beans. You should also include three to four servings of calcium-rich foods (such as yogurt or milk) for building strong bones. Also, having a little bit of fat will balance your diet, provide essential fatty acids, and assist with absorption of certain vitamins.
2. Should I stop eating red meat?
Stop eating fatty red meat. Too much fatty meat not only clogs your arteries, but it may also take the place of carbohydrates you could be eating, which can lower stamina.
Lean cuts of beef, pork, and lamb can be easily included in your diet. The Food Guide Pyramid recommends two 2- to 3-ounce servings of lean meat a day for a total of 5 to 6 ounces. Lean meats are excellent sources of not only protein but also iron and zinc, two minerals particularly important for athletes.
Keep portions small. Slice a small piece of lean steak into thin strips, then stir-fry it with veggies and serve with lots of carbohydrate-rich rice. Or add a little extra-lean hamburger to spaghetti sauce.
3. Should I take vitamin pills?
If you are active and have a good appetite, you can get a lot of vitamins in your diet. Unlike an inactive elderly person, who might eat 1,000 to 1,500 calories per day, an athlete may top 3,000 calories. By choosing wholesome foods, then, you can double or triple your vitamin intake. For example, if you drink 12 ounces of orange juice, you'll get 200% of the recommended dietary allowance (RDA) of vitamin C.
If you eat fewer than 1,500 calories per day, one multivitamin and mineral pill might be good. If you do not eat meat, iron and zinc supplements can be helpful. Note that some fortified breakfast cereals and energy bars provide 100% of the RDA for many nutrients.
But you need to eat well even if you take a supplement. Without a doubt, fruits and vegetables are the best sources of important nutrients. The ones with the most vitamins are oranges and orange juice, cantaloupe, strawberries, kiwi, bananas, green and red peppers, broccoli, spinach, tomatoes, carrots, and sweet potatoes. These powerhouse foods provide vitamins and may also guard against aging, cancer, heart disease, and other diseases.
4. Is an energy bar best for an afternoon snack before I work out?
An energy bar is a convenient, but expensive, calorie source. You can get the same energy from snacks such as yogurt, a banana and juice, a bagel, or fig cookies. Find out which foods settle best in your stomach.
The popularity of energy bars has highlighted the importance of eating before exercise. Fueling within an hour before you work out boosts stamina and endurance (1).
5. I don't drink eight glasses of water every day. Is that bad?
You don't have to drink water, per se, to fulfill your fluid requirement. Many foods are water filled: juice, oranges, lettuce, soup, yogurt, milk. Even coffee and tea provide water, but they tend to increase urination.
Because your fluid need is based on the calories you burn, you may need more than the proverbial eight glasses per day. You need 1 mL of water per 1 calorie burned. For an inactive person who requires about 2,000 calories per day, this comes to 2,000 mL, or about 8 glasses. Clearly, athletes who burn off 3,000 to 6,000 calories per day need even more fluids. The easiest way to tell if you are drinking enough is to monitor your urine: It should be clear in color.
6. Which is better to replace sweat losses--water or a sports drink?
Sports drinks are important during endurance exercise like marathons to help replace fluids and energy. This helps prevent both mental and physical fatigue. So if you exercise for more than an hour, a sports drink (or other source of water and carbohydrates) taken during the workout will provide the energy you need. If you are exercising for less than an hour, water is generally fine.
After a hard workout, you can easily replace carbohydrates and fluids with juices. Because sports drinks are dilute for rapid absorption, they are a weaker source of carbohydrates than juice. So you need to drink twice as much sports drink (about 32 ounces) to get enough carbohydrates, about 50 g (200 calories) every 2 hours after exercise (2).
7. How much should I weigh?
Because weight is largely under genetic control, look at your immediate and extended family. Genetics aside, the rule of thumb to estimate appropriate weight is:
This means a 5'8" woman should weigh around 140 pounds, and a 5'8" man, 154 pounds. This formula, though, does not account for bone structure and musculature. So add or subtract 10% if you have a large or small bone or muscle structure.
8. I do lots of fat-burning exercise and don't eat any fat. Why haven't I lost weight?
To lose weight, you have to burn off more calories than you eat. Some people do this by adding exercise. In the process, they lose fat but build muscle--and weigh the same.
Other people exercise but end up eating more. Even though they eat fat-free foods, they get plenty of calories that negate the deficit. Because fat creates a feeling of fullness, people who eliminate fat often tend to feel hungry and continue to eat. Those calories add up!
You might have better success if you include a small amount of fat with each meal. Most female athletes, for example, can lose weight on about 1,600 to 1,800 calories per day. Given that 25% of calories can appropriately come from fat, they can eat 35 to 50 g of fat per day.
9. How do I best gain weight?
To gain weight, you have to consistently eat more calories than when you are maintaining weight. The easiest way to do this is to drink extra fluids like low-fat milk or juices. Cranberry juice is particularly high in calories. Also, the carbohydrates in juices provide lots of energy for muscle-building exercise that helps you bulk up.
You can also eat extra snacks and larger portions at meals. You don't need expensive weight-gain drinks; they are simply high-priced calories-in-a-can. Simply eat and drink 500 to 1,000 more calories per day of wholesome foods.
10. I think my teammate has an eating disorder. What can I do?
Although resolving the problem should be left to professionals, you can tell your teammate that you are worried about her health. For example, mention that she seems unhappy or tired. Or maybe she has a poorly healing injury or can't finish workouts. When you focus on her health and happiness, she may listen. But if you talk about food and weight, she'll likely deny any problem.
Don't expect her to open up right away. Talk to her coach or parents, or give her lists of local resources. (Call the American Anorexia/Bulimia Association, Inc, at [212] 501-8351.) Remember that eating disorders can be life threatening.
Remember: You, your physician, and your nutritionist need to work together to discuss nutrition concerns. The above information is not intended as a substitute for appropriate medical treatment.
Ms Clark is director of Nutrition Services at SportsMedicine Brookline in the Boston area. She is a fellow of the American College of Sports Medicine, a fellow of the American Dietetic Association, and a member of its practice group, Sports and Cardiovascular Nutritionists (SCAN).
THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 2 - FEBRUARY 97
A high-carbohydrate diet makes you fat and hurts your athletic performance. Sounds hard to believe? It is--yet it's the premise of several carbohydrate-bashing diet books currently on the market.
These books (Enter the Zone, Protein Power, and Healthy for Life) all feature diets that supposedly hold the key to lifetime thinness. Their shared theme is that Americans should eat a high-protein diet, instead of the high-carbohydrate diet recommended by most health professionals. Some books even claim that a high-protein, low-carbohydrate diet prevents and treats heart disease, cancer, diabetes, and depression, and in the process, helps us reach peak physical and mental performance.
But do these books provide a better way to eat? No. Carbohydrate-bashing diet books claim that carbohydrates are bad because they raise blood sugar level and cause the release of insulin--a supposedly evil hormone that makes you fat. Insulin, it is said, causes high-carbohydrate food to be stored as fat rather than used for energy. Such claims are due for a reality check.
Reality Check 1: Carbohydrates and insulin don't make you fat.
Insulin isn't a harmful hormone. It's essential for the transfer of glucose (blood sugar)
from the bloodstream to the body's cells, where it fuels all activities. What matters in
weight loss isn't carbohydrates and insulin, but calories. Getting a high percentage of
your calories from carbohydrate doesn't make you fat, because weight depends only on how
many calories you take in relative to how many you burn off.
Paying attention to calories is critical for weight control. When people are encouraged to eat more carbohydrate and less fat, some get the wrong message. They think they can eat as much high-carbohydrate food as they want, as long as the food is fat-free. Consequently, they eat too many low-fat sweets and extra-large portions of starches. As a result, they can't lose weight and may feel that carbohydrates have "betrayed" them.
Cutting back on dietary fat does reduce total calories more than cutting back on carbohydrate, because fat supplies more than twice the calories by weight. In addition, fat is more likely to be stored as body fat than is carbohydrate. However, a person who cuts back on fat calories but adds them back in the form of carbohydrate calories is not going to lose weight. It's a simple matter of energy balance that holds true for people whether they're active or not (1).
Reality Check 2: High-protein, low-carbohydrate diets don't increase your ability to
burn fat.
No diet will help you gain better access to your body's fat stores during exercise.
Carbohydrate, not fat, is the primary fuel for exercise at or above 70% of aerobic
capacity, the intensity at which most people train and compete (2). Fat only becomes
available for fuel after about 20 minutes of exercise, and most people don't work out long
enough to directly burn significant amounts of fat during a workout. But regular exercise
can create a calorie deficit that promotes gradual fat loss over the long haul. Further,
aerobic exercise raises the level of several hormones that promote greater fat use (2).
Therefore, the best way to crank up your body's fat-burning ability is to keep working out
(3).
Reality Check 3: High-protein, low-carbohydrate diets aren't the answer for people
who are insulin resistant.
About 10% to 25% of all Americans are insulin resistant. These people are likely to have
high blood pressure, high blood triglycerides (fatty substances), and a low level of
high-density lipoprotein (HDL) cholesterol (the "good" kind), all of which
contribute to an increased risk of heart disease. The muscle, liver, and fat cells of
these people are less sensitive to the actions of insulin--most likely because they have
fewer insulin receptors.
When insulin-resistant people eat simple or complex carbohydrate, the pancreas compensates by dramatically increasing insulin secretion to maintain normal blood glucose levels. According to the carbohydrate-bashers, this oversecretion causes carbohydrate to be stored as fat, and therefore insulin-resistant people are best helped through low-carbohydrate, high-protein diets.
There is no good evidence, however, that insulin resistance or high blood insulin levels make people fat. The truth is that reducing excess weight and increasing physical activity are more important in treating insulin resistance than is the dietary percentage of carbohydrate or fat.
Weight loss and exercise both increase insulin sensitivity, and increased sensitivity results in lower blood insulin levels.(4) Weight loss allows the cells to "recognize" insulin more easily so that less insulin is required. Regular physical activity causes insulin to bind more easily to muscle cell receptors and to promote glucose uptake more effectively (4). Exercise and weight loss combined also have an additional benefit: They lower the risk of heart disease by reducing triglycerides, lowering blood pressure, and increasing HDL cholesterol.
Reality Check 4: High-protein, low-carbohydrate diets are not magic
regimens--they're just very low-calorie.
You'll lose weight on these diets because of the severe caloric restriction, not because
of what is supposedly happening to insulin levels. You'll eventually lose something else,
too: your performance and well-being. You need to eat enough calories and carbohydrate to
maintain your muscle stores of glycogen--the favored fuel for exercise. Following a
low-calorie, low-carbohydrate diet will only put you into a twilight zone of near
starvation.
Reality Check 5: You need carbohydrates to perform at your best.
When you eat carbohydrate, the body changes much of it into glucose, the chief source of
energy for the body. Glucose that is not needed immediately is stored as glycogen in the
liver and muscles for later use.
Although eating carbohydrate 30 to 45 minutes before exercise raises insulin levels and lowers blood glucose, these effects are temporary and will not harm performance. In fact, consuming carbohydrate an hour before exercise can improve performance (5). Carbohydrate feedings 3 to 4 hours before exercise also enhance performance by "topping off" glycogen stores (6). Consuming carbohydrate during workouts lasting longer than an hour aids endurance by providing glucose for your muscles when they're running low on glycogen (7,8). Finally, taking in carbohydrate right after several hours of hard training increases muscle glycogen storage (9).
Active people and athletes require dietary carbohydrate to maintain their muscle-stored glycogen, the predominant fuel for most sports. They gain weight only if they consume more calories than they expend. When this happens, they should blame their forks, not the carbohydrate.
So what's the bottom line on high-protein, low-carbohydrate diets? They supposedly make you a thinner, healthier, and better athlete. What they really do, though, is take the fun out of eating. Almost all professional health groups in the country recommend dietary variety--55% to 60% of calories as carbohydrate, 10% to 15% as protein, and the remainder as fat. And variety at the table adds spice to an active life.
Remember: You, your physician, and your nutritionist need to work together to discuss nutrition concerns. The above information is not intended as a substitute for appropriate medical treatment.
Ms Coleman is the nutrition consultant at The Sport Clinic in Riverside, California. She is a two-time finisher of the Hawaii Ironman triathlon and author of Eating for Endurance, 3rd edition (Palo Alto, CA, Bull Publishing, 1997).
THE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 8 - AUGUST 96
It seems like the more things change, the more they stay the same. For decades, dietitians told you to eat a balanced diet of a variety of foods and to eat in moderation. Then came news that antioxidants may help your body function better, prevent certain diseases, and relieve muscle damage and soreness after exercise. Dietitians wondered if eating whole foods was not enough and whether you should supplement your diet with antioxidants.
But currently, in light of new research (1), scientists are rethinking their recommendations about antioxidant supplements. So what's the final word? Even though the research gets confusing, learning more about antioxidants will help you make a decision.
Your body naturally produces chemicals called free radicals that cause irreversible damage (oxidation) to cells. They can leave your body vulnerable to advanced aging, cancer, cardiovascular disease, and degenerative diseases like arthritis.
Although your body has a natural antioxidant mechanism that protects you from most cell damage, certain environmental factors, like cigarette smoke, exhaust fumes, radiation, excessive sunlight, certain drugs, and stress, can increase free radicals. And, ironically, so can the healthy habit of exercising.
Fortunately, many substances in food act as antioxidants. Scientists have conducted studies, particularly on vitamins E and C, and the nutrient beta-carotene, to find out what role they play in protecting you.
Cardiovascular disease. One cause of heart disease is arterial plaque, which is the buildup of cholesterol (a fatty substance) on your artery walls. The main culprit of plaque buildup is thought to be the oxidation of low-density lipoprotein cholesterol (LDL-C).
Early studies (2,3) found that vitamin E decreases LDL-C oxidation. The greatest risk reduction occurred in men and women who took 100 mg of vitamin E per day (the recommended dietary allowance [RDA] is 12 mg for women and 15 mg for men). More recent research (4) found that the minimum dose of vitamin E needed to significantly decrease the risk is 400 mg per day.
But to confuse the issue, a study (5) on women who had gone through menopause refuted these findings. Women who ate moderate amounts of foods rich in vitamin E had about half the chance of dying from heart disease than women who avoided vitamin E-rich foods. But there was no decrease in risk for women who took vitamin E supplements.
Cancer. Because research (6) found that people who ate foods rich in vitamin C and beta-carotene lowered their risk of developing many cancers, scientists began to study whether supplements could help even more.
It may be too soon to tell. Many studies look promising, but two (7,8) completed within a year of each other showed such startling preliminary results that the researchers stopped the studies early. In both studies, smokers supplemented with beta-carotene had a greater risk of developing lung cancer than those who were not supplemented. And another study (9) found no evidence that supplementing with 50 mg of beta-carotene lowered death rates from cancer, heart disease, or any other causes.
During exercise, your body naturally produces more free radicals. Certain exercises, such as weight lifting or running downhill, can lead to muscle injury and soreness and the production of even more free radicals that can last for many days.
By far the most promising studies about antioxidants and exercise have centered around vitamin E. These studies (10,11) have shown that vitamin E reduces free radical production and oxidation related to exercise. In one of the studies (10), subjects over age 55 who ran and walked downhill benefited from a daily 800-mg vitamin E supplement. Subjects under age 30, however, did not benefit. The author concluded that as people age, their vitamin E levels decrease--but their need for them increases--and that supplements can help.
It seems clear that people who consume diets high in antioxidant-containing foods are protected from many chronic diseases. Even though research appears to be contradictory, it may be that the evidence has been somewhat misinterpreted. Perhaps the protection you get from food comes from the food itself and the combination of its compounds, rather than just the specific antioxidant it contains.
The amounts of vitamin C and beta-carotene that seem to be protective are easily obtained from food. To get enough of these two vitamins, follow the United States Department of Agriculture's Food Guide Pyramid recommendations (12). Strive to eat 3 to 5 servings of vegetables and 2 to 4 servings of fruits every day (table 1: not shown).
Getting enough vitamin E in your diet may be tricky because the greatest sources of vitamin E are foods rich in vegetable oils, like seeds, nuts, and wheat germ. Like many active people, you may be lowering your fat intake and not meeting the RDA for vitamin E. Try adding some vitamin E sources into your diet and don't be afraid of a little fat: A diet low in fat does not mean a diet devoid of fat.
If you still aren't getting enough vitamin E, a supplement of 100 to 400 mg per day is adequate. If you'd like to boost your intake of the other antioxidants as well, take a one-a-day vitamin-mineral supplement that contains antioxidants. Reasonable levels are 250 mg of vitamin C and 5 to 6 mg of beta-carotene.
When the research gets confusing, consider the entire body of evidence, and look for long-term trends. The evidence weighs heavily on the side of eating exactly as we've always been told: with balance, variety, and moderation.
Remember: You, your physician, and your nutritionist need to work together to discuss nutrition concerns. The above information is not intended as a substitute for appropriate medical treatment.
Dr Kleiner is a private nutrition consultant to athletes in the Seattle area. She is a member of the American College of Sports Medicine and of the American Dietetic Association and its practice group, Sports and Cardiovascular Nutritionists (SCAN), and a fellow of the American College of Nutrition.