Iron intake and body iron stores, anaemia and risk of hyperglycaemia among Chinese adults: the prospective Jiangsu Nutrition Study (JIN)

Objective: Fe supplementation has been used to prevent anaemia in China; however, high Fe intake and body Fe stores may increase diabetes risk. The present study aimed to prospectively examine the association between Fe intake/stores and hyperglycaemia, and to assess the joint effects on anaemia. Design: We followed 1056 healthy adults aged 20 years and older from 2002 to 2007. Body Fe stores were measured. Dietary data were collected using a 3 d food record and FFQ. Hyperglycaemia was defined as fasting plasma glucose. >5.6 mmol/l. Results: Of the participants, 28.8% were anaemic at baseline. During the 5 years of follow-up, we documented 125 incident cases of hyperglycaemia, among them twenty-three were diabetic. Haem Fe intake was positively associated with the risk of hyperglycaemia in men and women: the OR (95% CI) across increasing quartiles of haem Fe intake was 1.00 (referent), 1.49 (0.74, 3.01), 2.16 (1.06, 4.42) and 3.48 (1.71, 7.11), respectively (P for trend <0.001). Comparing the fourth quartile of serum ferritin with the others, the age- and gender-adjusted OR (95% CI) was 1.54 (1.01, 2.34), P for trend = 0.043. The association between total Fe intake and the risk of hyperglycaemia was significant in men (P for trend = 0.002). Anaemia added additional risk of hyperglycaemia on haem Fe intake. Comparing extreme quartiles of haem Fe intake, the OR (95% CI) was 5.67 (1.43, 22.49) and 3.44 (1.51, 7.85) for hyperglycaemia among anaemic and non-anaemic participants (P for trend = 0.008 and 0.010, respectively). Conclusions: The present cohort study suggests that high haem Fe intake, anaemia and high ferritin are associated with an increased risk of hyperglycaemia in Chinese men and women. There was a joint effect between anaemia and haem Fe intake on the risk of hyperglycaemia.