Nitrate intake linked to lower risk of early age-related macular degeneration

Total nitrate intake, especially from vegetable sources, is associated with the incidence of early age-related macular degeneration (AMD), reports a new Australia study.

Using a semi-quantitative food frequency questionnaire, researchers evaluated the dietary intake of 2,856 adults. Follow-up after 15 years was conducted on 2,037 participants (mean age 63.8±8.3 years; 43.3 percent male). AMD incidence, the main study outcome, was assessed from retinal photographs.

At baseline, 12.4 percent of the participants were current smokers and more than half (59.4 percent) consumed at least one serving of fish per week. The incidence rates of early and late AMD were 15.3 percent and 4.1 percent, respectively.

Dividing participants into quartiles according to energy-adjusted daily nitrate intake, researchers showed that those in the third quartile (119.5–162.3 mg/day; adjusted odds ratio [OR], 0.61; 95 percent CI, 0.41–0.90; p<0.05) were significantly less likely to develop early AMD than those in the first quartile. No significant differences were observed for the second and fourth quartiles (p=0.19 for trend).

Stratified analysis according to nitrate source showed that the protective effect of being in the third quartile remained significant for vegetable nitrates (adjusted OR, 0.65; 0.44–0.96; p<0.05) but not for nonvegetable nitrates (adjusted OR, 0.79; 0.54–1.17).

On the other hand, nitrate consumption was consistently unrelated to the risk of late AMD, regardless of source of daily intake volume.  

Though future studies are still required to confirm and strengthen the present conclusions, the findings of the current study indicate that adopting diets rich in nitrate sources such as beetroot and green leafy vegetables may potentially be a simple strategy to minimize early AMD risk, said researchers.