Effect of high-fat diet on phosphorus absorption

Objective: Dietary carbohydrate/fat ratio may affect phosphorus metabolism because both calcium and phosphorus are regulated by similar metabolic mechanisms, and a high-fat diet (HF) induces deleterious effects on the absorption of dietary calcium. We hypothesized that the HF induces an increase in phosphorus absorption; therefore, this study aimed to evaluate the effects of differences in the quantity and quality of dietary fat on phosphorus metabolism over the short and long term. Research Methods & Procedures: Eighteen 8-week-old Sprague-Dawley male rats were fed an isocaloric diet containing varied carbohydrate/fat energy ratio and sources of fat (control diet [Control], HF, and high saturated-fat diet [HF-SFA]). At 3 days and 7 weeks after the allocation and initiation of the test diets, feces and urine were collected and used for phosphorus and calcium measurement. Results: The fecal phosphorous concentration (F-Pi) was lower in the HF-SFA group than in the other two groups; however, the urine phosphorus concentration (U-Pi) was significantly higher in the HF-SFA group than the other two groups when the rats were fed over the short (p<0.01) and long term (p<0.01 vs Control group, p<0.05 vs HF group). There were no significant differences in type-IIa sodium-phosphate cotransporter (NaPi-2a) and type-IIc sodium-phosphate cotransporter (NaPi-2c) mRNA expression, which are renal phosphate transport-related genes; however, the expression of type-IIb sodium-phosphate cotransporter (NaPi-2b) and type-III sodium-phosphate cotransporter (Pit-1) mRNA in the duodenum was higher in the HF and HF-SFA groups than in the Control group (p<0.05), although there were no significant differences in these in the jejunum. Conclusions: Our results indicated that HF, particularly HF-SFA, increases intestinal phosphate absorption compared with Control