People who have high levels of oxidative stress due to chronic health problems might benefit from taking supplements of vitamin E in doses higher than the currently recommended daily intake, say experts in the US.
They are not the first to call for changes to the established RDA levels in the US (15mg), which is based largely on data that is decades old and does not really explore the optimal intake for people who have depressed levels of micronutrients due to athletic exertion, heart disease, or simple lack of physical activity, according to vitamin E expert Maret Traber.
Traber and colleagues at the Linus Pauling Institute at Oregon State University recently reported that ultramarathon runners who used supplements of vitamins C and E for six weeks prior to their races totally prevented the increase in lipid oxidation that is otherwise associated with extreme exercise.
But the type of metabolic damage observed in these runners is also often found after heart attacks, strokes, surgery and other traumas, said the researchers.
The study, published in the 15 May issue of Free Radical Biology and Medicine (36(10), pp1329-41), provides more evidence for the value of vitamin E supplementation as an antioxidant that, at the least, can help prevent damaging lipid oxidation and some of the health concerns associated with it.
The trial involved 22 runners who performed in a 50km 'ultramarathon'. Half of the runners were given daily supplements of 1,000 milligrams vitamin C and 400 international units of vitamin E for six weeks prior to the race, while the other half ate only their normal, healthy diet.
An analysis of biomarkers in the control group showed significant increases in lipid peroxidation following the race - these biomarkers were at levels that are often seen after someone has had a heart attack. The runners taking vitamins C and E were comparatively normal.
"This study clearly showed that supplementation with these antioxidant vitamins could help prevent the significant levels of lipid oxidation that are associated with intense exercise," said Angela Mastaloudis, co-author on the study.
She added that the people who did not take supplements but had a vitamin E intake around the amount recommended by US health authorities did not gain those protective benefits.
The findings may have ramifications far beyond people who undergo unusual exercise regimens. Oxidative stress and higher levels of lipid oxidation are seen in a wide range of health problems, ranging from diabetes to heart disease, stroke, Alzheimer's disease, smoking and even obesity, the researchers said.
"We often can't do dietary studies with people who are very ill, due to ethical concerns, so we used marathon runners to learn more about the effects of stress and ways to prevent damage from it. These athletes in a race can have a 10- to 20-times increase in whole body oxygen consumption."
"However, this study does suggest that people who have high levels of oxidative stress and lipid oxidation due to other chronic health problems might benefit from supplements of vitamin E that are higher than the current RDA for this vitamin," Traber said.
The research was published around the same time as a major conference on vitamin E, where experts sought to discuss findings to date and research needs for the future. Most participants agreed that not enough is yet known to recommend optimal intake levels.
Traber argues that some of the newer theories on the vitamin have little evidence behind them but that its role as an antioxidant is widely supported.
"One of the things we're finding more and more is that different antioxidants have fairly specific jobs that often don't overlap all that much. For instance, some claims have been made that vitamin E can play a role in preventing DNA damage, muscle fatigue, muscle damage or improved performance, and we simply don't find much evidence to support that," said Traber.
But when it comes to preventing lipid oxidation and the health concerns associated with that, vitamin E may be of profound benefit.
"I think it's pretty safe to say, at this point, that marathon runners should absolutely be taking supplements of vitamin E," Traber said. "A larger question is to determine who else could benefit."