In the news:Vitamins, Carotenoids & Age-related Cataract; B-vitamin Levels Clue to Omega-3 Brain Effects

Vitamins, Carotenoids May Lower Risk of ARC

Numerous studies suggest that dietary vitamins and carotenoids may be associated with a reduced risk of age-related cataract (ARC), but a quantitative summary of these associations has been lacking. That led university researchers in Xi’an China to conduct a meta-analysis of 8 randomized controlled trials (RCTs) and 12 cohort studies of vitamin and carotenoid intake and ARC risk (1).

Most of the nutrients evaluated in the cohort studies were significantly associated with a reduced relative risk for ARC including: Vitamin A (19%), Vitamin C (20%), Lutein or zeaxanthin (19%), and Vitamin E and beta-carotene (each 10%). In the RCTs, neither vitamin E nor beta-carotene reduced risk vs. placebo.

Further dose-response analysis indicated that in cohort studies the risk of ARC significantly decreased by 26% for every 10-mg/day increase in lutein or zeaxanthin intake and decreased by 18% for each 500-mg/day increase in vitamin C intake (P < 0.001, respectively).

The dose-response was more modest for beta-carotene at 8% risk decrease per 5-mg/day, and for vitamin A with a 6% risk decrease per 5-mg/day (P < 0.001, respectively).

“If we could delay the onset of ARC by 10 years, it could halve the number of people requiring surgery," stated one of the study’s co-authors.

Understanding Omega-3 Effects in Alzheimer’s

The OmegAD trial (2) was a 6-month double-blind trial in 204 mild to moderate Alzheimer’s patients randomized to 1.7 g DHA and 0.6 g EPA daily or placebo. The 1 outcome was cognitive change (measured by Mini-Mental State Examination or MMSE); the 2 outcome was clinical status (Clinical Dementia Rating Scale). The results showed positive effects only in a sub-group of patients with mild AD.

Significant interactions between omega-3 supple-mentation and baseline homocysteine levels on cognition and clinical stage were observed in the current analysis of OmegAD. In patients with elevated homo-cysteine (which reflects poor B-vitamin levels), supple-mental omega-3 significantly improved both measures of cognitive performance and clinical status.

B-vitamins (folic acid, vitamins B6 and B12) are necessary to form phosphatidyl choline, an important carrier of DHA and EPA in blood and across the blood brain barrier. So adequate B-vitamins could be important in delivering omega-3s to the brain.

An earlier RCT, VITACOG (3), evaluated high dose B-vitamins in mild cognitive impairment. Analysis found that a protective effect of the B vitamin intervention on brain atrophy rates was dependent on the plasma concentrations of DHA and EPA at the study’s start. Only those participants with high baseline plasma DHA and EPA showed lower rates (40%) of brain atrophy with the B-vitamin treatment vs. placebo.

Taken together, these findings suggest that both omega-3 and B-vitamin status are important in those with cognitive decline. The functional status of B-vitamins appears to be a relevant factor to consider when evaluating the effect of supplemental omega-3.

References

1. Hong Jiang, et al. Dietary vitamin and carotenoid intake and risk of age-related cataract. Am J Clin Nutr. 109: 43,54, 2019.
2. Jernerén F; et al. Homocysteine status modifies the treat-ment effect of omega-3 fatty acids on cognition in a randomized clinical trial in mild to moderate Alzheimer’s disease: The OmegAD Study. J Alzheimer’s Dis. Epub ahead of print, Apr 1, 2019.
3. Jernerén F, et al. Brain atrophy in cognitively impaired elderly: The importance of long-chain omega-3 fatty acids and B vitamin status in a randomized controlled trial. Am J Clin Nutr 102: 215-221, 2015.