A new paper in Biology Letters raises more questions about the benefits of vitamins as a health supplement.

High doses of dietary antioxidants such as vitamins are claimed to slow the process of cellular aging by lessening the damage to proteins, lipids and DNA caused by free radicals. Some research has found that the longevity of mice could be extended by administering particular vitamin supplements, despite the supplements' limited effectiveness in reducing free radical damage. However, the opposite was found to be true in voles in a new study.

Instead, vitamin C and vitamin E were found to dramatically reduce the lifespan of voles, found the biologists. The team fed field voles a diet supplemented with high levels of vitamin E or vitamin C from the age of two months in either warm or cold conditions and compared their longevity to groups of voles fed a regular diet.

Voles in cold conditions fed supplements of vitamin E or vitamin C lived much shorter on average than those fed a regular diet. Similarly, in warm conditions, supplemented voles fed vitamin E or vitamin C lived much shorter than those fed a regular diet. Compared to animals on a regular diet, lifespan was reduced by 11% and 26% for vitamin E and C voles in the cold and by 17% and 18% for vitamin E and C voles in the warm. Despite the effect on the voles' lifespans, the researchers found that the vitamin supplements did have some effect in decreasing free radical damage.

Kaplan–Meier survival curves of voles maintained in the cold (a) 7 ± 2°C or warm (b) 22 ± 2°C and given access to either a control diet, a vitamin E-supplemented diet or a vitamin C-supplemented diet from two months of age. (a) Solid blue line denotes control, stippled green line denotes vitamin E and broken orange line denotes vitamin C groups. (b) Solid red line denotes control, stippled green line denotes vitamin E and broken orange line denotes vitamin C groups. Credit and link:doi: 10.1098/rsbl.2013.0432

Professor Colin Selman of the University of Glasgow's Institute of Biodiversity, Animal Health and Comparative Medicine, who was first author on the work, said, "When we began our research, we expected that voles' lifespans would be boosted by the vitamin supplements in a similar way to the mice we had tested previously, so we were surprised to see that was not the case. Our findings suggest that major differences exist in the effects of high doses of antioxidants on oxidative damage and lifespan across species."

Professor John Speakman, of the University of Aberdeen, who led the work, said, "It's unlikely that randomized controlled trials examining the effects of antioxidant supplementation on human lifespan would be possible, so we are dependent on the results of animal studies. It's impossible at this stage to extrapolate the results from this small amount of data we have on voles and mice but it does suggest that caution is warranted in the use of high doses of antioxidant vitamins."

The work was funded by BBSRC.

Citation: Colin Selman, Jane S. McLaren, Andrew R. Collins, Garry G. Duthie and John R. Speakman, 'Deleterious consequences of antioxidant supplementation on lifespan in a wild-derived mammal', Biol. Lett. 23 August 2013 vol. 9 no. 4 doi: 10.1098/rsbl.2013.0432