Association between magnesium: Iron intake ratio and diabetes in Chinese adults in Jiangsu Province

Background: The intake of iron is positively related to the risk of diabetes, whilst magnesium intake is inversely related. However, it is unknown whether there is an interaction between dietary magnesium and iron expressed as a ratio and diabetes. Methods: This is a cross-sectional household survey carried out in 2002 in Jiangsu Province, China. A total of 2849 men and women aged ≥ 20 years participated (participation rate 89.0%). Iron and magnesium intake was assessed by 3-day weighed food records. Fasting plasma glucose, serum ferritin and haemoglobin were measured. Results: The mean intake of iron and magnesium was 25 mg/day and 332 mg/day, respectively. The prevalence of diabetes was 3.0% in men and 2.6% in women. Magnesium intake was negatively associated with diabetes when adjusted for age and sex, but not in a fully adjusted model. A strong inverse association between magnesium : iron intake ratio and diabetes was observed. In the fully adjusted model, the odds ratios of diabetes across quartiles of magnesium : iron intake ratio were: 1.0, 0.63 [95% confidence interval 0.32-1.25], 0.36 (0.16-0.81) and 0.48 (0.20-1.14) (P for trend 0.038). There was an interaction between central obesity and magnesium : iron ratio. Conclusion: Magnesium : iron intake ratio is an independent risk marker for diabetes in Chinese adults. As this is a cross-sectional study, we cannot establish any causal relationship.