Dietary supplements are good for athletes – aren’t they?

Athletes tend to adopt a healthy life-style, and today this seems to include the regular intake of a range of dietary supplements. Supplements specifically marketed for sports-people promote good health and performance, we are constantly told – but is this true?

A 2010 review found that “there is good evidence that caffeine can improve single-sprint performance, while caffeine, creatine and sodium bicarbonate ingestion have all been demonstrated to improve multiple-sprint performance. The evidence is not so strong for the performance-enhancing benefits of β-alanine or colostrum. Current evidence does not support the ingestion of ribose, branched-chain amino acids or β-hydroxy-β-methylbutyrate, especially in well trained athletes.”

However, a 2011 paper was considerably more cautious: “For most supplements, the evidence is weak, or even completely absent. A few supplements, including caffeine, creatine, and bicarbonate, are supported by a strong research base. Difficulties arise when new evidence appears to support novel supplements: in recent years, β-alanine has become popular, and the use of nitrate and arginine is growing. Athletes seldom wait until there is convincing evidence of efficacy or of safety, but caution is necessary to minimize risk.”

The review suggests that about 90% of sports supplements contain estrogenic endocrine disruptors, and about 25% of them having a higher estrogenic activity than acceptable. About 50% of the supplements are contaminated by melamine, a source of non-protein nitrogen. Additional data accumulate toward the safety of nitrate ingestion. In the last 2 years, the safety of emerging supplements such as higenamine, potentially interesting to lose weight, creatine nitrate and guanidinoacetic acid has been evaluated but still needs further investigation.

The authors of this article claim that “the consumption of over-the-counter supplements is very popular in athletes. Although most supplements may be considered as safe when taking at the recommended doses, athletes should be aware of the potential risks linked to the consumption of supplements. In addition to the risks linked to overdosage and cross-effects when combining different supplements at the same time, inadvertent or deliberate contamination with stimulants, estrogenic compounds, diuretics or anabolic agents may occur.”

Despite these cautions, the market for supplements is growing and the myth that supplements are good for health continues. The truth is, however, more complex and far less encouraging:

• It is impossible to generalise across the entire range of highly diverse supplements.
• Some have positive effects.
• The vast majority do nothing at all.
• Most are quite harmless.
• Some can have serious adverse effects.
• All of them cause harm to your bank account.