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In the news: Vitamin C & Artery Health, Lutein & Brain Function

Vitamin C Especially Vital for Those at Risk of CVD

The results of a new review suggest that vitamin C provides benefits for certain groups of people. In the study (1), British scientists report that vitamin C in doses higher than 500 mg daily may improve functioning of the inner lining of blood vessels (the endothelium), and support heart heath for those who need it most – those with diabetes, atherosclerosis and heart failure.

The endothelium helps maintain the elasticity of blood vessels and helps regulate the activity of white blood cells (neutrophils) that are a key component of the immune system. Impaired endothelial function can lead to arteries that are not as supple, raising the risk of hypertension. Poor endothelial function can also lead to arteries that are chronically inflamed.

Forty-four randomized controlled trials involving more than 1,100 participants were included in this meta-analysis and systematic review evaluating the effect of supplemental vitamin C on endothelial function.

The meta-analysis showed a significant positive link between the dose of vitamin C and improvement in endothelial function. The effect of vitamin C supple-mentation also appeared to be dependent on health status, with stronger effects seen for those who are more at risk for cardiovascular disease.

These beneficial effects may be due to vitamin C’s ability to help keep oxidative damage and vessel inflammation in check, as well as increasing the availability of nitric oxide, a compound that dilates vessels and helps maintain endothelial function.

Role for Lutein in Supporting Brain Function?

One exciting topic discussed at the International Carotenoid Society (ICS) meeting held this July, was the potential role of the carotenoids lutein and zeaxanthin in cognitive function, e.g. the process of knowing, perceiving, and remembering.

lutein and zeaxanthin are the only two carotenoids that cross the blood barrier of the retina to form the eye’s macular pigment. Studies have found that these two carotenoids also accumulate in the brain in preference to other carotenoids in our diets such as alpha and beta-carotene, lycopene and beta-cryptoxanthin.

The concentration of lutein and zeaxanthin in the eye’s macula corresponds to the concentration of these carotenoids in brain tissue. So researchers now consider macular pigment density to be a ‘bio-marker’ of lutein / zeaxanthin levels in the brain (2). This is intriguing because a significant correlation between macular pigment density and measures of cognitive function has been seen in studies of older individuals (3).

lutein / zeaxanthin have antioxidant and anti-inflammatory effects, and help stabilize cell membranes – actions which are important for healthy cognition. The Center for Nutrition, Learning and Memory has been established at the University of Illinois to better understand exactly how and where these carotenoids work in the brain.

Results of the cognitive function sub-study from the AREDS2 trial were announced at the ICS meeting. While the study found no association between lutein / zeaxanthin supplementation and cognitive function overall, the researchers have not yet ruled out the possibility that supplements made a difference for those whose dietary intake of these carotenoids was low at the study’s start.

In contrast to the AREDS2 findings, several small, exploratory studies have reported promising results. In a 4-month double blind, placebo controlled study, verbal fluency scores improved in older women given supplemental lutein, DHA or both nutrients. Memory scores and rates of learned also improved in the combined treatment group (4).

References

1. Ashor AW, et al. Effect of vitamin C on endothelial function in health and disease: A systemic review and meta-analysis of randomized controlled trials. Atherosclerosis 235:9-20, 2014.
2. Johnson EJ. Review. A possible role for lutein and zeaxanthin in cognitive function in the elderly. AJCN 96(suppl):1161S-5S, 2012.
3. Vish-wanathan  R, et al. Macular pigment optical density is related to cognitive function in older people. Age Aging 43:271-5, 2014.
4. Johnson EJ et al. Cognitive findings of an exploratory trial of DHA and lutein supplementation in older women. Nutr Neurosci 11:75-83, 2008.