Omega-3 DHA may boost eyesight, but fails to affect mental function: Study

15-Mar-2012 - Last updated on 15-Mar-2012 at 15:29 GMT

Three months of supplementation with DHA may boost eyesight in older people, but the omega-3 did not affect cognitive function, says a new triple-blind placebo-controlled randomized trial.

A daily supplement providing 252 mg DHA and 60 mg EPA led to a 4% improvement in eyesight, report researchers from Swinburne University of Technology in Australia and United BioSource Corporation in the UK.

“The finding that 90-day DHA administration brought about an improvement to visual acuity in participants with corrected vision is encouraging,” they wrote in Neurobiology of Aging.

“In consideration of the high incidence of vision impairment in the elderly, and the increasing proportion of the population that makes up this demographic, this finding is worthy of further investigation.”

Omega-3s

A link between omega-3 and eye health has been reported previously, mostly in relation to its potential to reduce the risk of AMD (age-related macular degeneration).

DHA is known to be a major structural and functional component of the photoreceptor of the retina (93% of the omega 3 fatty acids and 30% of total fatty acids), and a 2008 study published in the American Journal of Clinical Nutrition (Vol. 87, pp. 1521-1529) indicated that DHA increases the macular pigment optical density (MPOD).

Furthermore, a meta-analysis by Australian scientists reported that a high intake of omega-3 fatty acids and fish may reduce the risk of AMD by up to 38% (Archives of Ophthalmology, 2008, Vol. 126, pp. 826-833).

New data

The Neurobiology of Aging study adds to this body of evidence and indicates that DHA may boost eyesight in a healthy aging population.

Seventy four healthy people aged between 45 and 77 were recruited to participate in the triple-blind placebo-controlled randomized repeated-measures trial. They received either a daily DHA supplement (1000 mg of tuna oil, providing 252 mg per day of DHA, 60 mg EPA and 10 mg vitamin E) or placebo (soybean oil) for 90 days.

Results showed that there were no changes in measures of cognitive function between the groups.

“There is the possibility that with a larger sample size significant cognitive effects associated with DHA supplementation may have been found. Similarly the possibility remains that significant cognitive effects may have been found if a higher dose of DHA or longer treatment duration was used,” wrote the researchers.

This view was shared by Harry Rice, PhD, VP of regulatory & scientific affairs for GOED, the omega-3 trade group. Dr Rice told NutraIngredients-USA: "One need only look at MIDAS (published in 2010) to know you can demonstrate an effect in a similar population. Thus said, it is my opinion that the no effect in the current study was a result of being too short, using too low a dose and in general under-powered."

The researchers did, however, report a significant improvement in eyesight was observed in the omega-3 group, a result described by the researchers as “encouraging”.

“These findings lend support to previous research which has associated DHA with improved membrane function in the lens and retina and better performance in brightness discrimination tasks,” they added.

The study used the HiDHA product from Sydney-based Clover Corp., and the company partly funded the trial.

Source: Neurobiology of Aging
April 2012, Volume 33, Issue 4, Pages 824.e1-824.e3, doi: 10.1016/j.neurobiolaging.2011.03.019
“The effects of 90-day supplementation with the Omega-3 essential fatty acid docosahexaenoic acid (DHA) on cognitive function and visual acuity in a healthy aging population”
Authors: C. Stough, L. Downey, B. Silber, J. Lloyd, C. Kure, K. Wesnes, D. Camfield