Calcium study points to lower AMD risk

Higher calcium intake was linked to a markedly lower likelihood of age-related macular degeneration in a Chinese case-control study that adds fresh evidence to a growing debate over whether diet can help shape the course of one of the world’s leading causes of vision loss in older adults. The findings, published on 14 April in Food & Function, suggest that calcium from dairy foods such as milk and yoghurt may be associated with the strongest effect, though the researchers stopped short of claiming a direct cause-and-effect relationship.

The study was carried out within the Xi’an Eye Study and analysed 284 people with age-related macular degeneration alongside 284 matched controls who underwent eye examinations and completed a detailed food frequency questionnaire. After adjusting for multiple factors, the authors found that people with higher dietary calcium intake had significantly lower odds of having the disease. Comparing the highest and lowest thirds of calcium intake, the odds ratio was 0.46, indicating substantially lower likelihood among those consuming more calcium.

The association appeared strongest in participants whose calcium intake was below 800 mg per 2,000 kcal a day, a detail that matters in a country where calcium consumption has long trailed recommended levels. Among the main food sources assessed, only dairy-based calcium showed a statistically significant inverse association. People who drank milk at least four times a week had lower odds of age-related macular degeneration than those who rarely or never consumed it, while those eating yoghurt at least twice a week also showed lower odds. No significant association was found for milk powder, vegetables or legumes as calcium sources.

That nuance is likely to shape how the findings are read by clinicians and public health specialists. The paper does not argue that calcium alone protects eyesight, nor does it prove that adding milk or yoghurt to the diet will prevent disease. Case-control studies can identify associations, but they cannot establish causation with the same confidence as long-term prospective trials or randomised interventions. Diet also tends to travel with other factors, including income, health awareness, access to care and broader lifestyle habits, which can influence outcomes even after statistical adjustment.

Still, the study lands in a field where nutrition has long been viewed as one of the few modifiable elements in macular degeneration risk. Age-related macular degeneration affects the macula, the central part of the retina needed for sharp vision, and it is a leading cause of vision loss among older adults. Global estimates published in The Lancet Global Health projected that 196 million people would be living with the condition in 2020, rising to 288 million by 2040. In mainland China alone, a modelling study published this year estimated that 32.42 million people aged 40 to 89 were living with some form of the disease in 2020, with overall prevalence at 4.70 per cent.

The Chinese findings also fit into a broader, if still unsettled, body of evidence. A 2023 study indexed on PubMed likewise reported that lower dietary calcium consumption was associated with higher risk of age-related macular degeneration in a Chinese population. Earlier work from the US National Eye Institute found no evidence that calcium intake increased risk and suggested that higher intake might even be protective in some groups, while stressing that the evidence was not strong enough to justify changing calcium use specifically to prevent the disease.

What strengthens the relevance of the new paper is the nutritional backdrop. Multiple studies indicate that calcium intake in China remains well below recommended thresholds for a large majority of adults. One 2025 China CDC Weekly analysis reported that 96.1 per cent of adults had calcium intake below the estimated average requirement, while earlier nutrition work found median intake levels near half the recommended amount. Against that backdrop, the researchers’ emphasis on a population with relatively low calcium intake is more than a technical detail; it may help explain why dietary differences were easier to detect.

For ophthalmologists and nutrition researchers, the practical message is measured rather than dramatic. The paper supports the view that adequate calcium intake, particularly through dairy foods, may sit within a broader pattern of healthier ageing and eye protection. It does not overturn established guidance that smoking, age and genetic predisposition remain central risk factors, and it does not suggest supplements should replace balanced diets or regular eye checks. What it does offer is a more specific clue about how everyday nutrition may intersect with retinal health in populations where calcium intake is habitually low, giving researchers a clearer path for the next round of prospective studies.