Dietary Iron Intake and New-Onset Hypertension: A Nationwide Cohort Study from China

The relationship of dietary iron intake with the risk of hypertension remains uncertain. We aimed to investigate the prospective association between dietary iron intake and new-onset hypertension among Chinese adults.A nationwide cohort study.Using data from seven rounds of the China Health and Nutrition Survey (CHNS) from 1997 to 2015.A total of 12,245 participants without hypertension at baseline were included in this study.Dietary intake was measured by three consecutive 24-h dietary recalls combined with a household weighing inventory.The study outcome was new-onset hypertension, defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg or diagnosed by physician or currently under antihypertensive treatment during the follow-up.During a median follow-up of 6.1 years, 4,304 (35.1%) participants developed hypertension. Overall, there was a U-shaped association between dietary total iron intake and new-onset hypertension (P for nonlinearity0.001), with the lowest risk observed at 18.2-22.1 mg/day (quintile 2-3). Similarly, a U-shaped association between dietary nonheme iron intake and new-onset hypertension was found (P for nonlinearity0.001), with the lowest risk at 17.4-21.3 mg/day (quintile 2-3). However, the association between dietary heme iron intake and new-onset hypertension followed a L-shape (P for nonlinearity0.001), and a significantly lower risk of new-onset hypertension was found in participants with quintile 2-5 of dietary heme iron intake (adjusted HR, 0.75; 95% CI: 0.68, 0.82), compared with those in quintile 1 (0.25 mg/day).The association between dietary iron and new-onset hypertension was nonlinear in Chinese adults, following a U-shape for total or nonheme iron intake, and a L-shape for heme iron intake.