Objectives: 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.
Design: A nationwide cohort study.
Setting: Using data from seven rounds of the China Health and Nutrition Survey (CHNS) from 1997 to 2015.
Participants: A total of 12,245 participants without hypertension at baseline were included in this study.
Exposures: Dietary intake was measured by three consecutive 24-h dietary recalls combined with a household weighing inventory.
Measurements: 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.
Results: 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 nonlinearity <0.001), 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 nonlinearity <0.001), 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 nonlinearity <0.001), 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).
Conclusions: 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.
Keywords: CHNS; Dietary iron; heme iron; new-onset hypertension; nonheme iron.