Association Between Dietary Intake of Phosphorus and Measures of Obesity in the Jackson Heart Study.

ABSTRACT

BACKGROUND: The relation between phosphorus (P) intake and obesity is equivocal, with hypotheses in both directions. OBJECTIVES: We investigated the relationship between P intake, assessed from a current database, and calculated bioavailable P intake and obesity among African-American adults. METHODS: We examined associations between original and bioavailable P (total, added, and natural) and BMI and waist circumference (WC) in a cross-sectional study of 5306 African-American adults (21-84 y) from the Jackson Heart Study. A total of 3300 participants had complete interviews, valid dietary data, and normal kidney function. Diet was assessed by food frequency questionnaire. A novel algorithm was used to estimate P bioavailability. BMI or WC was regressed on each P variable, adjusting for total energy intake and potential confounders. RESULTS: After adjusting for covariates, original P (total and added) and bioavailable P (total and added) intakes (expressed/100 mg) were associated with BMI (ß 0.11, 0.67, 0.31, and 0.71, respectively; all P < 0.0001). Neither original nor bioavailable natural P was significantly associated (ß -0.03 and 0.09, respectively; both P > 0.05). When added and natural P were included in the same model, added P (original and bioavailable) intakes remained strongly associated with BMI (0.70 and 0.73, respectively; both P < 0.0001). Similar results were seen for WC. Intake of original added P tended to be more strongly associated with BMI, in females (ß 0.72; P < 0.0001) than in males (ß 0.56; P = 0.003) (P-interaction = 0.06). CONCLUSIONS: We found that greater intake of added, not natural, which may be a proxy for intake of processed foods was associated with higher BMI and WC. These were somewhat stronger when bioavailability was considered and for women than for men. Further investigation is needed to fully understand the mechanisms driving these associations.