antioxidant diets

Antioxidant Diets: Low antioxidant diets may hamper fuel delivery

Although the jury’s still out on the pros and cons of antioxidant supplementation for athletes, a consensus of scientific opinion is beginning to form around the notion that low antioxidant intakes are undesirable for various reasons. The latest evidence comes from a new Australian study on the relationship between reduced levels of dietary antioxidants and levels of free fatty acids in the blood (free fatty acids are a major fuel source for humans at rest and during moderate intensity exercise, when blood levels rise markedly).

Seventeen trained athletes followed a restricted antioxidant diet, markedly different from their normal diet, which was designed to supply only a third of the normal levels of the antioxidant vitamins C and beta-carotene. All the subjects underwent submaximal and incremental exercise testing to exhaustion on two occasions – the first while consuming their habitual high antioxidant diet and the second after two weeks on the low antioxidant diet. After both tests, blood was analysed for fatty acid content.

The results were intriguing because, although the same types and amounts of fats were consumed with both diets, the circulating levels of blood fatty acids, particularly omega-3 and omega-6, were significantly reduced on the low antioxidant diet. Moreover, although exercise time to exhaustion was the same for both diets, athletes reported a higher perceived rate of exertion during submaximal exercise on the low antioxidant diet.

Although it’s not possible to draw firm conclusions from just one study, this provides evidence that dietary antioxidants not only play a crucial role in protecting the body from free radical damage but may also be required for the mobilisation of free fatty acids, which are a major source of fuel during exercise.

Lipids, 2005; 40(4):433-5

Help at hand for footballer’s headache

Headache is very common among sportsmen and women – particularly, it seems, among footballers. According to a recent unpublished survey of elite professional Australian football, about 80% of players had regular headaches, of which one third could be classified as migraine.

But now help is at hand in the form of a nasal spray which has been shown to be highly effective in a pilot trial of professional Australian footballers.

Players were asked to report to their club doctor when they developed a headache and, in the absence of contraindications, were treated with a single dose of 20mg sumatriptan nasal spray. Players were asked to record the severity of the headache at 30 minutes, two hours and 24 hours after the treatment.

In all, 38 attacks were analysed in 26 footballers, seven of them being migraine with aura, 10 migraine without aura, 11 moderate or severe but non-migrainous and the remaining 10 mild.

The two-hour response showed that 86% of attacks of migraine with aura and all the attacks of migraine without aura responded to treatment, with complete relief reported by 71% of those with migraine with aura and 90% of those without aura. Recurrence rates were generally low, with no migraine headaches and 25% of non-migraine attacks recurring at 24 hours.

Players were judged able to return to match play after treatment in 31 attacks (82%), with the remainder of headaches occurring during training or when concurrent injuries – eg concussion – prevented further participation. In players who returned to match participation after treatment, no deterioration in performance was evident.

Minor side effects of treatment, most commonly an unpleasant taste in the mouth, were reported in 28 attacks.

The researchers point out that treatment of headache in professional sport is often difficult, with many conventional treatments, including beta-blockers, caffeine and codeine- containing preparations, banned.

Sumatriptan, on the other hand, ‘has no known performance enhancing properties and can be used in professional and Olympic sporting events’.

The results of this trial must be treated with a degree of caution since participants were not ‘blinded’ to treatment and no untreated placebo group was included for purposes of comparison.

‘This… trial suggests,’ conclude the researchers, ‘that sumatriptan nasal spray may be a valuable, effective and convenient treatment of headache in professional sport. A randomised placebo controlled trial would be appropriate to confirm these preliminary results.’

Br J Sports Med 2005; 39:552-554

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