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.