Nitrates offer protection against age-related macular disease

Dietary nitrate intake contributes to a lower risk of age-related macular disease (AMD), although this association seems to disappear when Mediterranean dietary patterns are taken into account, according to a study.

The study used data from the prospective Age-Related Eye Disease Study (AREDS) and AREDS2 randomized clinical trial cohorts and their extended follow-up studies. The combined cohort included 7,788 participants (AREDS: n=4,288; AREDS2: n=3,610 participants [110 participated in both studies]) who had nonlate AMD in at least one eye.

The cohort had a mean age of 71.1 years, and 56 percent were women. In total, 13,511 eligible eyes were examined. Researchers looked at the potential association between dietary nitrate intake and development of late AMD (neovascular AMD [nAMD] or geographic atrophy [GA]) or large drusen. They also examined the interactions of dietary patterns with common at-risk single-nucleotide polymorphisms.

Compared with the lowest quartile of dietary nitrate intake, the highest quartile was associated with a lower risk of progression to late AMD (hazard ratio [HR], 0.77, 95 percent confidence interval [CI], 0.69–0.86) and a decreased risk of GA (HR, 0.71, 95 percent CI, 0.61–0.83) and nAMD (HR, 0.85, 95 percent CI, 0.73–0.99) in the combined cohort.

In AREDS alone, the highest quartile of nitrate intake appeared to have a protective effect on the risk of late AMD (HR, 0.77, 95 percent CI, 0.65–0.91) and GA (HR, 0.80, 95 percent CI, 0.65–0.97) but not nAMD. Meanwhile, in AREDS2, increased nitrate intake had a null association with late AMD (HR, 0.90, 95 percent CI, 0.80–1.02) and nAMD (HR, 0.93, 95 percent CI, 0.78–1.11).

Of note, dietary nitrate intake was correlated with Mediterranean dietary patterns (p<0.001).

The present data may be subject to potential bias and are hypothesis-generating in nature, thereby precluding them from supporting new clinical recommendations. More studies are needed before dietary nitrate intake can be recommended as a therapy for AMD.