Science of Sport: Supplements

Diane Back checks out a second batch of over-the-counter potions claiming to boost athletic performance

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Given the range of supplements available and the intensity with which they are promoted, it is very easy for an athlete to be sidetracked into chasing the latest fad and neglecting their basic diet, training and recovery regimes.

One athlete I know of was popping more pills per day than your average pensioner and spending in excess of £100 a month. His daily intake included:

• 1 x multi vitamin
• 1 x multi mineral
• 1 x Vitamin C mega dose
• 1 x Vitamin B complex
• 1 x Vitamin E
• 1 x chromium picolinate
• 3 x creatine supplements
• 1 x calcium tablet
• 1 x echinacea tablet
• 1 x ginseng tablet
• 1 x gingko biloba
• 1 x omega fish oil
• 3 x garlic tablet

If your client is similarly attached to pillpopping, it may be worth reminding them that their habit has more base in faith than science. Published studies will often show positive results for a specific sport or activity, but be contradicted by other studies trying out the supplement for a different sport. They may show benefits for men but not for women. And crucially, they usually involve taking the trial supplement in massive doses which are not commercially supplied.

If your athlete is preoccupied with supplements, you should consider undertaking a thorough review of their eating habits and diet. Supplements are not a substitute for a balanced diet and in certain sports, especially those where weight is an issue (gymnastics, dance, power lifting etc), there may be something more serious developing. Do not forget the female triad, where young women will take supplements in an attempt to convince themselves they are eating properly.

Having said this, for certain athletes in your care, a multi-vitamin and mineral supplement is a good idea:

Vegetarians and vegans: pay particular attention to the Vitamin B complex. It is well recognised that the vegan and vegetarian diet tends to be deficient in Vitamin B and athletes are no exception.

Diabetic athletes: there is evidence that diabetics may well have poor zinc and magnesium absorption from the gut, and healing from injuries may be slow because of imbalances in their blood sugar metabolism.

Athletes with digestive disorders: this includes Crohn’s disease, ulcerative colitis etc. An iron supplement may also be advisable.

Patients with a gluten intolerance would benefit from seeing a specialist sports dietician. Many power bars, gels and drinks have gluten in them.

Caffeine

What is it?

A naturally occurring substance found in numerous plant leaves, nuts and some types of seeds. We consume it in tea, coffee, carbonated drinks and overthe- counter medications, such as painkillers and flu remedies. In drinks the dose is usually 30-50mg and in medications it can be as high as 100- 200mg per tablet.

How does it work?

It has long been believed that caffeine improves endurance performance by increasing fat-burning, thereby sparing glycogen stores. This is contentious though: we do not know the actual mechanism by which caffeine may do this; it has a very short-lived and inconsistent effect; and some athletes fail to respond at all.

Is there any evidence for its use?

There is evidence that it works in certain sporting situations, such as in intense bursts of activity (1-5 minutes), and in long- and ultra-endurance events of continuous activity (four hours duration or more). Most studies have been laboratory based and there is little done on athletes in the field.

Any adverse side effects?

Higher doses of caffeine are known to increase heart rate and over-stimulate the individual. This could affect performance and prolong recovery time. From studies done (on non-athletes) involving experimental tasks to test motor control, it is reasonable to suggest that in sports requiring fine motor control and technique, caffeine can have a detrimental effect on coordination.

Should you recommend it?

Until recently caffeine was on the World Anti Doping Codes prohibited list. It has now been removed. There are no specific sports formulations, although the newer drinks (eg Red Bull and guarana-based drinks) are promoted as suitable for athletes. The current recommended dose is 6mg/kg body weight, taken one hour before sport.

There is sound evidence that caffeine can improve performance in some circumstances, but there is no evidence that bigger doses are more effective and many athletes do not respond at all. It is probably not worth bothering with.

Probiotics

What are they?

In official blurb, they are a ‘live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance’. Otherwise known as friendly and very trendy bacteria. The ones we mainly encounter are lactobacillus acidophilus and bifidobacterium bifidum, often added to dairy based products such as yoghurt, although they are also available in capsule, tablet and drink forms.

How do they work?

The claims for the benefits of probiotics are widespread and extravagant: a reduced incidence of cancers, reduced lactose intolerance, increased bioavailability of nutrients, reduced allergic sensitivity, improved immunity – to name just a few. However, very little exists in the literature to help us understand the mechanism of action.

Is there any evidence for their use?

I have been unable to find any evidence that they improve performance in athletes, although one study reported by the Australian Institute of Sport did state that lactobacillus fermentum reduced the symptom days of distance runners. I can’t enlighten you further, because the study does not explain.

Any adverse side effects?

There are reports of bacteraemias (bacterial infection in the bloodstream) and endocarditis (heart valve bacterial infection) in immuno-compromised patients, and gastrointestinal disturbances in patients with digestive tract disorders.

Should you recommend them?

It’s hard to justify using probiotics as a supplement when you can obtain them from a properly balanced diet that contains dairy products.

Glycerol

What is it?

A three-carbon molecule similar to alcohol. It occurs naturally in the body as a component of stored fat.

How does it work?

When it is eaten in a large single dose it is distributed throughout the body and exerts an osmotic effect that causes the body to retain water. Studies have suggested that up to 600ml of fluid may be retained. This could in theory benefit endurance athletes where dehydration can be an issue.

Current suggested dosages are 1.0- 1.5mg/kg body weight combined with 25-35ml of fluid. You need to follow specific loading protocols for proper absorption, from 2.5 hours to 1 hour before exercise. If the event lasts more than two hours, it may be advisable to ingest a 5% glycerol solution at the rate of 400-800ml/hour during the event.

Is there any evidence for its use?

Yes and no! There has been extensive research done on athletes in the field, showing decreased urine volumes and a 20% improvement in performance, based on increased time taken to fatigue. Other studies have shown no improvement in performance – but questions have been raised about the conduct of these studies. Until 1997 glycerol was classified as a diuretic by the doping agencies and was thus a banned substance. But since research has shown that it is not a diuretic (it does not act on the kidneys to increase urine output), it is no longer banned.

Any adverse side effects?

Some athletes have reported headaches and gastrointestinal disturbances after ingestion.

Should you recommend it?

Glycerol may be helpful for:

• endurance athletes where adequate hydration is a problem;
• rehydration in athletes where dehydration has been used to reduce weight to make a weight category;
• swimmers in endurance races.

HMB

What is it?

β hydroxy β methylbutyrate. It is a natural compound that the human body makes following metabolism of the amino acid leucine. The body uses it to make cholesterol. We produce 0.2- 0.4mg of HMB daily. As a supplement it is used to reduce muscle breakdown after exercise and improve repair.

How does it work?

HMB is believed to have a protective effect on muscle tissue during exercise. When athletes are exercising hard, their bodies in theory cannot make enough HMB to help protect their muscle cells, thus some people advocate increasing the intake of HMB to make up the deficit.

Studies suggest that 3g per day in several doses is the optimum regime. Larger doses don’t show any added benefit.

What evidence is there for its use?

Quite a bit, if your aim is to increase body mass. A number of studies have shown that HMB promotes an increase in lean body mass and a reduction in fat. One study from Poland showed the biggest improvements from a combined regime of HMB and creatine supplementation.

On the other hand, I have been unable to find any studies that suggest any improvements in performance.

Any adverse side effects?

None reported to my knowledge.

Should you recommend it?

It’s debatable, and will depend on the athlete’s goals. It is widely used in the body-building industry.

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