Use of dietary supplements and hormones in adolescents: A cautionary tale

Abstract

Ergogenic aids, such as nutritional supplements, anabolic steroids and human growth hormone, are increasingly being used to enhance sports performance or body image. While few rigorous scientific studies have derived significant conclusions, the marketing and promotion of most supplements is intense and far exceeds the data supporting their use. Particular concern has arisen regarding safety in the use of these substances among adolescents, who may be at particular risk when using caffeine-ephedra and anabolic steroid combinations. Indeed, long-term effects and fatalities have been reported. As a consequence, the American Academy of Pediatrics has condemned the use of anabolic steroid use for bodybuilding or performance enhancement in adolescents. Health care professionals need to educate themselves about ergogenic use and ask informed questions of their adolescent patients. An honest discussion of the limitations of most supplements, and acknowledgement that some supplements may work some of the time, may allow the physician to be more credible and useful in providing medical care and guidance to the adolescent seeking to improve body image or athletic performance.

‘NUTRITIONAL’ SUPPLEMENTS

The field of nutritional supplementation for ergogenic benefit is complex and rapidly changing. Natural health products do not require a prescription and are available for self-care and self-selection. It is important to note that the number of studies with rigorous scientific methodology that have derived significant conclusions is small, whereas the intensity of the marketing and promotion of most nutritional supplements is intense, far exceeding the data supporting their use (1). The most common supplements currently used are amino acids, creatine, protein powder, caffeine, ephedrine-type alkaloids (derived from the herb ma huang), ginseng, vitamin C, vitamin E, multivitamins, copper, magnesium and zinc (Table 1). Many supplements are marketed and promoted on the basis of various theoretical benefits that may be derived from limited animal studies, without any proven basis for recommending their use by humans for specific ergogenic benefits. Approximately 50% of the general population and up to 100% of athletes in some sports have reported taking some form of dietary supplement (1,2).

TABLE 1.

A paediatrician’s glossary of ergogenic aids

Ergogenic agent	Purported actions	Proven effects	Side effects
Amino acid mixtures: arginine, lysine, ornithine	Increases exercise-induced HGH release via oral ingestion.	Pre-exercise oral amino acid supplementation does not augment HGH release. No increased exercise benefit above exercise alone.	Large doses cause stomach discomfort and diarrhea.
Anabolic steroids: androstenedione, dehydroepiandrosterone (DHEA)	Improves muscle mass and strength beyond inherent genetic limits.	Few studies of how DHEA affects anabolic activity in younger athletes whose levels are already very high.	Long-term use associated with liver tumours, severe arteriosclerosis, myocardial infarction, stroke and premature death due to severe tissue-damaging effects, some of which are irreversible.
Arginine	Needed for periods of growth and recovery after injury; precursor for protein, creatine and nitric oxide biosynthesis; increases HGH release.	Very high intakes may increase HGH levels, but lower doses do not increase HGH release and may even impair HGH release in younger adults.	None at usual doses.
Carnitine	Improves skeletal muscle function and athletic performance in healthy individuals	No compelling evidence that carnitine supplementation improves physical performance in healthy subjects.	Oral carnitine doses of several grams cause no significant clinical toxicity.
Chromium	Promoted as a nonsteroidal anabolic hormone to increase lean body mass.	No specific ergogenic effect has been demonstrated.	Interferes with iron and zinc metabolism; addition of ephedrine to chromium can cause hypertension, stroke and death.
Copper	Critical nutrient.	No studies have demonstrated a specific ergogenic effect from supplementation beyond usual dietary intake.	Excessive supplementation can cause GI distress, nausea, vomiting and diarrhea, as well as intravascular hemolysis.
Creatine	Provides increased power during anaerobic, short-duration, high-intensity activity.	No benefit on endurance exercise or maximal oxygen uptake. Not tested in those younger than 18 years.	Significant negative effects, mostly GI cramping and distress.
Ginseng	Increases resistance to catabolic effects of exercise, with a secondary consequence of prolonged time to exhaustion with extreme exercise.	None of the proposed mechanisms of action have been proven, nor have the benefits been demonstrated.	Bioavailability may be low, with no active ginseng in some products. Excess leads to hypertension, insomnia, diarrhea and irritability, but all or some of these effects may be due to coexistent ephedrine or ma huang.
Glucosamine	Regenerates cartilage and aids joint lubrication and shock absorption, and has anti-inflammatory effects.	No direct evidence that repair or protection occurs in vivo, or that the use of glucosamine sulfate changes articular cartilage either structurally or functionally.	In North America, glucosamine is a highly purified derivative of shellfish, which may provoke allergic reactions.
Magnesium	Increases physical power through increased muscle mass, with an associated increase in aerobic power and endurance.	There is no proven effect on performance.	Excessive intake causes GI upset, nausea, vomiting, diarrhea, muscle weakness and interference with the absorption of calcium.
Multivitamins: A and D, B complex, may include many minerals	Helps meet increased requirements of intense exercise and training.	10 to 50 times the recommended daily intake of all or some of these vitamins for up to nine months did not improve aerobic performance. Can address dietary deficiencies due to calorie restriction or high carbohydrate intake.	Hypervitaminosis A may cause bone resorption and bone abnormalities. Hypervitaminosis D causes anorexia, nausea, vomiting, constipation, weakness and weight loss. Both cause hypercalcemia.
Ornithine	Promotes muscle building by increasing levels of anabolic (growth-promoting) hormones such as insulin and HGH.	Most human research does not support these claims at reasonable intake levels.	Very high amounts cause many GI side effects.
Vitamin E	Reduces delayed-onset muscle soreness in eccentric exercise.	There is no known benefit at low-altitude exercise, and no performance improvement or effect on VO2 max in endurance athletes.	Can act as an anticoagulant and may increase the risk of bleeding problems.
Zinc	Increases muscle contraction strength, explosive power and power endurance.	No evidence of a measurable ergogenic effect in controlled studies.	Can cause copper deficiency and interfere with tetracycline activity.
Amphetamines, ephedrine	Stimulates exercise performance.	May increase time to exhaustion by masking the physiological response to fatigue, but have not been shown to result in any significant performance improvements.	Anxiety, tremor, tachycardia and hypertension. Can increase blood glucose and lactate.
Caffeine	Stimulates exercise performance.	The potential benefits of caffeine are lost in several confounding variables. Most studies show minimal to no benefit in untrained, recreational athletes. Caffeine plus ephedrine may increase performance during submaximal steady-state aerobic exercise.	Anxiety, tremor, tachycardia and hypertension. High caffeine intake may accelerate bone loss. Combinations of caffeine with other stimulants (eg, ephedrine) have been linked to fatal events.
Narcotic analgesic	Allows extension of exercise performance.	Not necessarily ergogenic.	Harmful if used to allow participation of an athlete with a severe injury.
Marijuana, cocaine	Enhances athletic performance.	Marijuana does not increase strength. Cocaine and other sympathomimetic drugs have little or no effect on athletic performance.	Addictive and illegal.

GI Gastrointestinal; HGH Human growth hormone; VO₂ max Maximal oxygen consumption. Data from references 1 to 3

Dietary supplements are not required to meet the United States Food and Drug Administration requirements (3), but Health Canada has established new guidelines for over-the-counter products (4). Natural health products are defined in Health Canada regulations as vitamins and minerals, herbal remedies, homeopathic medicines, traditional medicines (such as traditional Chinese medicines), probiotics, and other products such as amino acids and essential fatty acids. Under the new regulations, the product must be safe for consideration as an over-the-counter product. It is important to note that nonhormonal supplements, such as vitamins, minerals and amino acids, may contain anabolic steroids that are not declared on the labels of the products (5).

Very few studies have examined the performance benefits of long-term, nonanabolic supplement use (1,2). A frequently cited study (6) performed at the Australian Institute of Sport comprised 82 elite athletes in four sports – basketball, gymnastics, rowing and swimming. Athletes were randomly assigned in a controlled, blinded fashion to their usual diet or a diet with a markedly enhanced intake of vitamins and minerals – 10 to 50 times the recommended daily intake of vitamins A, B₁, B₂ (riboflavin), B₆, B₁₂, C, E, folate, calcium, phosphorus, aluminum, copper, magnesium and zinc. Athletes were followed for up to eight months to assess performance and side effects. Athletes on the supplemented diet had significantly increased blood levels of several vitamins, but no benefit to athletic performance was seen.

Concern has arisen regarding the safety of the use of performance-enhancing substances in adolescents (7–10). Few safety studies of supplements have included adolescents, who may be at particular risk when using caffeine-ephedra and anabolic steroid combinations. In a study (7) of 742 high school athletes, 38% used supplements. The most common reasons given by the athletes for nutritional supplement use were to promote healthy growth, prevent illness and improve performance. Sixty-two per cent believed that supplement use improved athletic performance (7). The variety of supplements used may have significant implications for the medical care of adolescents (Table 1), who do not regularly inform their physicians about their use. Health care professionals need to educate themselves about supplement use and ask informed questions to their adolescent patients (8–10).

ANABOLIC STEROIDS

In response to the controversy over the use of anabolic steroids (2, 11–13), the American Academy of Pediatrics has condemned their use for bodybuilding or performance enhancement in adolescents (12). However, abuse of anabolic steroids, such as androstenedione and dehydroepiandrosterone, to increase muscle mass is a serious problem not only among professional athletes but also among bodybuilders and teenagers (12). Among high school students, 3% to 12% of males and 1% to 2% of females admit to anabolic steroid use at some time (13). Long-term effects and fatalities due to anabolic steroid abuse have been reported, including liver tumours, myocardial infarction, stroke and severe arteriosclerosis (Table 1). A significant black market has been established in the gym culture, but studies of anabolic steroids bought on the black market have shown that 35% do not contain the expected ingredients (11).

HUMAN GROWTH HORMONE

Human growth hormone (HGH) has a number of accepted medical uses due to its anabolic effect on protein metabolism, but it has become a popular ergogenic aid among athletes (2,14). The supraphysiological effects of HGH lead to lipolysis, with increased muscle volume (14). HGH may also be used for its anabolic effect, but data on this effect are lacking in adolescents. Due to the ethical limitations of studying the use of high doses of HGH in isolation or combined with anabolic steroids, the scientific literature has not produced compelling results on its efficacy. HGH has led to some improvement in athletic performance in isolated studies (2,14). Despite the lack of compelling data, HGH has developed a reputation among athletes for enhancing performance (2,14).

PROGRAMMED INTERVENTION: INNOVATION LEADING TO IMPROVED ADOLESCENT HEALTH

An innovative prospective controlled trial (15) of 18 high schools, including 928 students from 40 participating sports teams, was designed to prevent young female high school athletes’ disordered eating and body-shaping drug use. Balanced random assignment was used to assign the schools to the intervention (eight weekly 45 min sessions) or to usual-care control conditions. Experimental athletes reported significantly less ongoing and new use of diet pills, and less new use of performance-enhancing substances (amphetamines, anabolic steroids and sports supplements). Other health-harming actions were also reduced (eg, fewer instances of riding with an alcohol-consuming driver, more seat belt use and less new sexual activity). The experimental athletes had coincident positive changes in strength-training self-efficacy and healthy eating behaviours. Thus, sports teams can be effective natural vehicles for peer-led curricula to promote healthy lifestyles in adolescents and to deter disordered eating, performance-enhancing substance use and other health-harming behaviours.

CONCLUSIONS

Amateur and professional athletes use numerous ergogenic aids that claim to enhance sports performance. Although some studies have indicated a performance benefit in particular athletic situations, there are few available data regarding efficacy or safety in competitive or noncompetitive adolescents (8–14). Common ergogenic aids include nutritional supplements, anabolic steroids and HGH. Physicians can evaluate these products by examining four factors that can help them counsel their adolescent patients: method of action, available research, adverse effects and legality. However, athletes report that their most common sources of dietary and supplement information to be (in rank order) their trainer or coach, a family member or friend, magazines and books, a physician and a nutritionist (1). While most adolescents may not seek information about ergogenic benefits from medical professionals, they may seek information about side effects or contraindications if the physician is open and nonjudgemental. An honest discussion of the limitations of most supplements, and acknowledgement that some supplements may work some of the time, may allow the physician to be more credible and useful in providing medical care and guidance to the adolescent seeking to improve body image or athletic performance.