Sports Supplements: Reduce oxidative stress

Antioxidants compared

Sports Supplements reduce oxidative stress

A fruit and vegetable juice concentrate is as good as a high-dose vitamin supplement at reducing the oxidative stress caused by intense aerobic exercise. That’s the implication of a new US study – the first to compare these two forms of antioxidant treatment on exercise-induced oxidative stress.

Intense and prolonged aerobic exercise can generate destructive chemicals known as reactive oxygen/nitrogen species (RONS), sometimes called ‘free radicals’. When your body produces RONS in amounts that overwhelm its natural antioxidant defence system, you are said to be suffering from oxidative stress. A growing body of evidence has implicated oxidative stress as a contributory cause of various degenerative diseases, including diabetes, certain cancers and heart disease.

The researchers in this study set out to compare the effects of two antioxidant formulas on biological ‘markers’ of oxidative stress before and after aerobic exercise. Forty-eight aerobically trained men and women were assigned to one of three treatments which they took daily for two weeks, as follows:

  • Antioxidant vitamin supplements – 400 international units (IU) of vitamin E and 1,000mg of vitamin C daily;
  • A mixed fruit and vegetable juice powder concentrate taken in capsule form and containing 108 IU of vitamin E and 276mg of vitamin C;
  • Placebo – a dummy treatment.

The athletes completed an initial submaximal exercise bout – a 30-minute run at 80% of VO2max – immediately before the two weeks of supplementation. They repeated it at the end of the two weeks and for a third time after a one-week ‘washout’ period without the supplements.

Blood samples were taken before and immediately after exercise and analysed for levels of three markers of oxidative stress: protein carbonyls (PCs), malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG) as well as vitamins C and E.

Key findings were as follows:

  • Blood levels of vitamin C and E were increased after taking the vitamin supplements but not the fruit and vegetable juice concentrate;
  • Both the active treatments modified the exercise-induced increase in PCs, with no significant difference between them;
  • This suppression of PCs following exercise was partially maintained for both of these treatments during the third exercise bout after the week-long washout period;
  • Neither treatment had any impact on the other two markers of oxidative stress – MDA and 8-OHdG.

The researchers had initially assumed that the vitamin supplements would provide greater protection against oxidative stress than the juice concentrate since they delivered higher doses of antioxidant vitamins. But, despite the fact that blood levels of vitamins E and C were higher after taking vitamins than after taking concentrate, both treatments yielded similar results in relation to suppressing protein oxidation.

The researchers acknowledge that the protection afforded by both these treatments against oxidative stress was limited and modest.

But, as they point out, ‘The finding that supplementation with a fruit and vegetable juice concentrate can provide protection against exercise-induced oxidative stress in a similar manner as higher dosages of vitamins C and E deserves attention. This is true especially in light of research suggesting adverse health outcomes with higher-dose, long-term vitamin E supplementation’.

Med Sci Sports Exerc, vol 38, no 6, pp1098-1105

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