Association of dietary calcium and its food sources with age-related macular degeneration in China: a population-based case-control study.

Background & aims: Recent studies, primarily in developed countries, suggest that higher dietary calcium intake is associated with lower odds of age-related macular degeneration (AMD). However, evidence on this association is lacking in China, where the population has unique dietary patterns and relatively low calcium intake. The aim of this study was to investigate the association of dietary calcium and its major sources with the likelihood of AMD in a Chinese population. Methods: A case-control study was performed within the frame of the Xi'an Eye Study. A total of 284 AMD cases and 284 matched controls who completed the eye examination and a detailed semi-quantitative food frequency questionnaire were included in the present analysis. Multivariable-adjusted conditional logistic regression models were applied to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of dietary calcium and its main sources. Results: In the multivariable adjusted model, an increasing amount of dietary calcium intake was associated with significantly lower odds of AMD, especially among participants with a dietary calcium intake of less than 800 mg per 2000 kcal per day. The OR for the comparison of the top with the bottom tertile of dietary calcium intake was 0.46 (95%CI: 0.23, 0.90; P-trend = 0.02). Regarding major sources of calcium, a significant inverse association was only observed for dairy-based calcium intake, with an OR of 0.45 (95%CI: 0.23, 0.89; P-trend = 0.02). Consumption of dairy products, particularly milk (OR: 0.45 from a comparison of ≥4 servings per week with never/rarely; 95%CI: 0.22, 0.90; P-trend = 0.05) and yogurt (OR: 0.38 from a comparison of ≥2 servings per week with never/rarely; 95%CI: 0.19, 0.78; P-trend = 0.01), was also associated with lower odds of AMD. No significant associations were found for milk powder or dietary intake of calcium from vegetables or legumes. Conclusions: Higher intake of calcium and its major food sources, such as milk and yogurt, was associated with a significantly decreased likelihood of AMD in a Chinese population with relatively low dietary calcium intake. These findings align with current public health recommendations for maintaining adequate calcium status and emphasize that the health implications of calcium may depend on its dietary sources.