Pills or produce? The truth about antioxidants

You and I are browsing through a health food store, amidst aisles packed with antioxidant elixirs. They all claim to halt our inevitable enemy: free radicals. As a by-product of breathing and metabolism, there’s no way to stop free-radical formation. It seems our only defense is simple – stock up on as many antioxidants as possible. But which ones?

The antioxidant story is a complicated one. Not only are there dozens of antioxidant types, but how they interact with each other under various conditions is virtually impossible to define. Vitamins A and C were the first antioxidants discovered over 100 years ago, followed by vitamin E in the mid- 20th century. These three are the most thoroughly researched. But judging from the number of pill bottles and powdered concoctions, there’s more to antioxidants than the ace vitamins. We’re now blasted with terms like carotenoids, flavonoids, anthocyanins and phenols, and expected to make a purchase. There’s very little agreement, however, on how these molecules interact with each other, let alone how much we should consume.

Before we leave the store, let’s review the basics. Scientists rate an antioxidant’s power by measuring its total capacity to absorb free radicals. So if a food has a high capacity, it’s assumed to be a very healthy food. But scientists don’t know if this does anything helpful in our bodies. We don’t really know how the properties found in berries, herbs, citrus, teas, wines and chocolate translates into what they actually do. These foods are regularly cited as antioxidant powerhouses and are dehydrated, pulverized and put into pills to be sold in high concentrations – in an attempt to make them even more powerful.

Admittedly, powdered smoothies are quicker to create and enjoy than downing a whole grapevine. But a consistent theory in the complicated scientific research is that more is not necessarily better. There are several other factors at play. For instance, if you don’t eat enough carbohydrates during exercise, it stresses the body, disrupting immune function in the two-hour post-workout window. Immune function is also compromised when total energy intake or diet quality is poor – so it’s critical to eat well all the time, not just after your workout. Total energy intake and diet quality affect performance; high doses of antioxidants may not.

The reason mega-doses may not matter is due to training benefits. When training volume and intensity increase, cells are at a higher risk of free-radical damage. A training benefit beyond cardiovascular and muscular adaptation is immune adaptation – our ability to suppress oxidant damage improves as we get in better shape. Aerobic metabolism from running produces a particularly high number of free radicals from the increase in oxygen consumption, but the body’s natural defenses correspondingly heighten, too.

Some studies on mega-dosing suggest higher intake levels actually hurt cellular training adaptations. The immune system simply can’t adapt to the training stress with too many antioxidants doing the work for it. When taken in Health Canada’s daily recommended doses (see table) we know these antioxidants help to prevent cell damage. But the question remains, will more make me a better runner?

It’s true, a regular runner is under constant oxidative stress. But there is no evidence that antioxidant supplements above tolerable upper limits – the point at which the risk of side effects occurs – enhance physical performance. Unless you limit dietary intakes of fruits, vegetables, and whole grains, vitamin C pills will not help you cut seconds off your running times. If you’re trying to lose weight while training by cutting back on healthy fats and whole grains, you could be compromising your immune response to training. Here, a vitamin E pill could help. But supplementary vitamins won’t help if your intake is around Health Canada’s daily recommendations. Take more than the upper tolerable limit and antioxidants can oxidize themselves.

To date, there haven’t been any large placebo controlled,  double-blind studies defining how  much of which antioxidant to consume and when.  An intriguing study of Ironman athletes in Austria  revealed some promising direction, however. Athletes  maintained their antioxidant intakes within the  daily-recommended doses throughout the duration  of the study, eating only food sources of antioxidants.  They took no supplements.

The researchers found immediately post-race,  vitamin C and total antioxidants increased significantly  in blood, as cells responded to the oxidant  attack. Shortly after the race however, other antioxidants  decreased while vitamin C stayed the same.  Carotenoids (found in orange and red fruits and  vegetables) and vitamin E (found in whole grains and nuts) blood levels  dropped the most. Researchers concluded that vitamin C levels were maintained  because the athletes tended to consume vitamin C food sources, but  carotenoid and vitamin E levels dropped because they didn’t eat those foods  after a race. They argued that the study illustrated how important a diversified  and well-balanced diet was to maintaining antioxidant status – before, during  and especially immediately after endurance efforts.

Whether supplementation is useful to prevent  oxidative stress, or detrimental by interfering with  beneficial physiological effects of exercise training,  remains a hot debate. The battle is mostly fought on  health food store shelves. Rather than boosting antioxidant intake beyond  normal levels, eating a varied, balanced diet seems to be the best prescription  for success. Despite flashy labels and easy-to-open pill bottles, we can maintain  a well-functioning immune system by regularly eating a variety of fruits,  vegetables and whole grains. Rather than stressing over which antioxidant to  buy, let’s walk over to the produce section and stock up on colourful foods.  Until science definitely disproves fresh vegetables, my money is on produce.

– Bobbi Barbarich