CAROTENOIDS IN ALZHEIMER’S

Supplementation with macular pigment carotenoids can restore pigment to the macula and bring about a significant improvement in the contrast sensitivity of Alzheimer’s disease patients, a recent study suggests.

“What we found in our interventional supplement trial was that we were able to rebuild the pigment in these patients, and the implication of that in a six-month period is that we were able to improve patients' vision,” lead investigator John Nolan PhD, Macular Pigment Research Group, Vision Research Centre, Waterford Institute of Technology, Ireland, told EuroTimes in an interview.

The randomised, double-blind trial involved 31 Alzheimer's disease patients and 31 age-controlled patients of a similar age who received six months of supplementation with either Macushield, consisting of 10.0mg meso-zeaxanthin, 10.0mg lutein and 2.0mg zeaxanthin, or sunflower oil as a placebo. At the end of the trial, both the Alzheimer’s disease and control patients receiving the supplement had significant increases in serum concentration of the three supplemented carotenoids, significant increases in central macular pigment, and significant improvements in contrast sensitivity. (Nolan et al, Journal of Alzheimer’s Disease 44 (2015) 1157–1169)

SIGNIFICANT RESULTS

Specifically regarding the improvements in contrast sensitivity, among those receiving the active supplement, paired sample t-tests from five spatial frequencies tested showed significant results for four spatial frequencies in the Alzheimer’s disease group, and for two spatial frequencies in the control group. The improvement in the Alzheimer’s disease patients was equivalent to a gain of one line on the Pelli-Robson chart.

Dr Nolan noted that the rationale of the trial was the findings of a previous study he and his associates conducted. It showed that in 36 patients with moderate Alzheimer’s disease the central macular pigment and macular pigment volume were significantly lower than in 33 control patients (p<0.001 for both).

The Alzheimer’s disease patients also had lower best corrected visual acuity (BCVA), contrast sensitivity, and lower serum concentrations lutein and zeaxanthin than the control patients (p<0.05, for all). (Nolan et al, Journal of Alzheimer’s Disease 42 (2014) 1191–1202)

The findings of the two studies add to a growing body of evidence suggesting that deficiency of macular pigment carotenoids in the central nervous systems may play a role in the cognitive decline of Alzheimer’s disease patients, Dr Nolan said. However, neither of the groups receiving the active supplement had any cognitive improvements, suggesting that the carotenoids may have a protective rather than a restorative effect regarding Alzheimer’s disease pathology, he added.

New clinical trials are currently under way testing the impact of the supplements in patients with mild cognitive impairment.

John Nolan: jmnolan@wit.ie