Skip to main content

  • Impact of Dietary Nitrate on AMD

    By Jean Shaw
    Selected and reviewed by Neil M. Bressler, MD, and Deputy Editors
    Add to My Bookmarks

    Journal Highlights

    JAMA Ophthalmology, February 2023

    Download PDF

    Does a high intake of dietary nitrate have an impact on the progression of age-related macular degeneration (AMD)? Broadhead et al. addressed this question in an analysis of data from the Age-Related Eye Disease Study (AREDS) and AREDS2. They found that higher nitrate intake was associat­ed with a lower overall risk of progres­sion to late AMD, including both late AMD subtypes: neovascular AMD and geographic atrophy (GA). However, much of this association was confound­ed by participants’ plant-based dietary patterns. Such patterns tend to be rich in foods that supply nitrates, such as leafy greens.

    In AREDS and AREDS2, validated food frequency questionnaires were administered to all participants (N = 7,788). For this post hoc analysis, the researchers performed regression anal­yses for the outcomes of progression to late AMD or large drusen. They also explored potential interactions with other dietary components, including lutein and zeaxanthin, and performed a genetic risk analysis. The combined AREDS/AREDS2 cohort comprised 4,396 women and 3,392 men. All self-identified as White, and their mean age was 71.1 years. There were 13,511 eligible eyes at baseline—and by final follow-up, 4,575 eyes (33.9%) had progressed to late AMD.

    In the AREDS/AREDS2 cohort, those with the highest dietary intake of nitrate (quartile 4) had the lowest risk of progression to AMD (hazard ratio [HR], .77 (95% CI, .69-.86 for quartile 4 vs. quartile 1). These HRs were .71 (95% CI, .61-.83) and .85 (95% CI, .73-.99) for GA and neovascular AMD, respectively. However, when the studies were considered separately, nuances emerged: in AREDS, increased nitrate intake was associated with a decreased risk of GA but not neovascular AMD—and in AREDS2, there was no associ­ation between nitrate intake and late AMD.

    With regard to genetic interactions with nitrate intake, associations were not statistically significant by genotype; however, this analysis was conducted in only a subset of participants. As for other dietary components, high intake of a number of vitamins, minerals, and healthy fats were positively correlated with nitrate intake, and it was not possible to disentangle their individual impact on AMD outcomes.

    In their discussion, the authors cautioned that the results of this study do not support recommending nitrate supplementation. However, as they point out, “Much of the outcome associated with nitrate intake can be at­tributed to plant-based dietary patterns in general, such as a Mediterranean diet.” (Also see related commentary by Michael Larsen, MD, DMSc, in the same issue.)

    The original article can be found here.