Dietary Zinc Intake and Its Association with Metabolic Syndrome Indicators among Chinese Adults: An Analysis of the China Nutritional Transition Cohort Survey 2015

The dietary zinc consumed in Chinese households has decreased over the past decade. However, the national dietary zinc intake in the last five years has seldom been investigated. Using data from 12,028 participants 18 to 64 years old (52.9% male) in the China Nutritional Transition Cohort Survey (CNTCS) 2015, we describe the intake of dietary zinc and the contributions of major foods and we examine the relationship between the level of dietary zinc intake and metabolic syndrome indicators, including blood pressure, fasting glucose, and triglycerides (TG), in Chinese adults. We assessed dietary zinc intake using 24 h recalls on three consecutive days. The mean daily dietary zinc intake for all participants was 10.2 milligrams per day (males 11.2 mg/day, females 9.4 mg/day, p < 0.001). The mean daily dietary zinc density for all participants was 5.2 mg/day per 1000 kilocalories. Among all participants, 31.0% were at risk of zinc deficiency, with dietary zinc intakes of less than the Estimated Average Requirement (EAR) (males 49.2%, females 14.8%, p < 0.050), and 49.9% had adequate dietary zinc intakes, equal to or greater than the recommended nutrient intake (RNI) (males 30.7%, females 67.0%, p < 0.050). We found substantial gender differences in dietary zinc intake and zinc deficiency, with nearly half of the men at risk of zinc deficiency. Males of younger age, with higher education and incomes, and who consumed higher levels of meat, had higher zinc intakes, higher zinc intake densities, and higher rates of meeting the EAR. Among all participants, grains, livestock meat, fresh vegetables, legumes, and seafood were the top five food sources of zinc, and their contributions to total dietary zinc intake were 39.5%, 17.3%, 8.9%, 6.4%, and 4.8%, respectively. The groups with relatively better dietary zinc intakes consumed lower proportions of grains and higher proportions of livestock meat. For males with adequate dietary zinc intake (≥RNI), TG levels increased by 0.219 millimoles per liter (mmol/L) compared with males with deficient dietary zinc intake (<EAR). For females in the ≥RNI group, diastolic blood pressure decreased by 0.963 millimeters of mercury (mmHg) and fasting glucose decreased by 0.187 mmol/L compared with females in the <EAR group; in addition, TG increased by 0.097 mmol/L in females in the ≥RNI group and by 0.120 mmol/L in females in the equal to or greater than the EAR and less than the RNI (EAR-RNI) group compared with females in the <EAR group. Adequate dietary zinc was associated with reduced diastolic blood pressure and fasting glucose levels in female Chinese adults, but with raised TG levels in all Chinese adults. We recommend strengthened nutrition interventions for Chinese males and lower socioeconomic subgroups.