Calcium intake and hypertension among obese adults in United States: associations and implications explored

The relationship between calcium intake and hypertension is receiving increased research attention. The prevalence of hypertension is high among the obese populations. Calcium is a mineral that influences blood pressure. The aim of the study was to examine the association between calcium intake and hypertension in a large nationally representative sample of obese American adults. A total of 14 408 obese adults aged 20 years or older were obtained from the 1999-2010 National Health and Nutrition Examination Survey. Analysis of variance and linear regression models were used to examine relationships between calcium intake and systolic blood pressure (SBP) as well as diastolic blood pressure (DBP). Multiple logistic regression models were used to examine the association between calcium intake and hypertension after adjusting for potential confounders and interactions, including: age, race, education level, alcohol use, smoking, diabetes status, sodium intake and potassium intake. Calcium intake was significantly lower for the hypertensive group compared with the normotensive group (P < 0.0001), especially among those obese female young adults aged 20-44 years and among non-diabetic obese adults. Based on ordinary linear regression analysis, a significant inverse relationship was detected, SBP and DBP decreased if calcium intake increased (SBP: regression coefficient estimate = -0.015, P < 0.0001; DBP: regression coefficient estimate = -0.028, P < 0.0001). Multiple logistic regression showed that calcium intake was negatively associated with the probability of hypertension (odds ratio (OR) = 0.81, 95% confidence interval (CI): 0.74-0.87, P < 0.0001). In stratified analysis, calcium intake in youngest adults (age 20-44 years) had the lowest likelihood of hypertension (OR = 0.77, 95% CI: 0.64-0.93, P < 0.0001), the inverse relationship between calcium intake and probability of hypertension was stronger among females (OR: 0.68, 95% CI: 0.55-0.84, P < 0.0001), when compared with the whole sample including all of 14 408 obese adults. The protective effect of calcium intake and hypertension was found significantly in obese non-diabetic adults (OR: OR = 0.77, 95% CI: 0.67-0.89, P < 0.0001) not in obese diabetic adults. SBP, DBP and calcium intake were log transformed for both ordinary linear regression analysis and logistic regression analysis. Our study findings underscore the need to explore the physiological mechanism between calcium intake and hypertension. In this study, increased calcium intake was associated with the lowest risk of hypertension. Future studies utilizing longitudinal research designs are needed to quantify therapeutic levels of calcium for control of hypertension among obese adults. Increasing calcium intake among American adults may offer promise as a cost-effective strategy to improve hypertension among obese adults; however, further scientific exploration is warranted.