Low B vitamin status has been shown to increase the risk of memory problems and dementia in the elderly. Trials using supplements of B vitamins have found benefits to cognitive performance, possibly because B vitamins are required for the production of important neurotransmitters. Antioxidant vitamins have also shown beneficial effects in preventing the oxidative stress that can lead to neurodegeneration. Supplementation with antioxidant vitamins may therefore be beneficial to cognitive function if taken in sufficient doses to reduce oxidative stress. The brain is particularly vulnerable to oxidative stress because of the high concentrations of polyunsaturated lipids which can undergo lipid peroxidation. The difficulty with researching vitamin supplements are the confounding variables that generally make interpretation of epidemiological data difficult. Those taking vitamin supplements are more likely to be non-smokers, to take regular exercise and also to have a higher overall diet quality.
The use of clinical trials to assess the benefits of vitamin intake on cognitive performance has been reported in the literature. For example, researchers1 from France used data from the SU.VI.MAX double blind randomised controlled trial which involved 4447 French subjects aged between 45 and 60 years. Between 1994 and 2002, participants took an antioxidant vitamin supplement that contained 120mg vitamin C, 6mg of β-carotene, 30mg vitamin E, 100µg selenium and 20mg zinc, or a placebo tablet. When the cognitive performance of the subjects was assessed between 2007 and 2009 with 4 neuropsychological tests, it was found that the subjects receiving the antioxidant vitamin supplement had significantly higher scores for episodic memory. In addition, principle component analysis showed that verbal analysis was improved following antioxidant vitamin supplementation, but only if the subject was a non-smoker, or who had low baseline vitamin C concentrations.
These results support the hypothesis that antioxidant vitamins are beneficial at improving some aspects of cognition in the elderly. The antioxidant supplement used in this trial contained only low doses, and these amounts would be attainable in the diet if it was of high quality. It is important to understand that the effects of vitamin supplements are likely due to corrections of sub-clinical deficiencies, and those with adequate vitamin status through diet will not benefit through supplementation. Another important consideration is that high doses of single antioxidant vitamins can have pro-oxidant effects in vivo, and therefore antioxidant supplements should always contain combinations of vitamins as in this study. For example, supplementation of β-carotene to smokers has been shown to increase the risk of lung cancer in more than one study, most probably because of increased rated of oxidative stress.
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