Calcium restriction for 28 days markedly and negatively influences bone mineral density of the femur and lumbar vertebrae regardless of the high-fat diet ingestion in young adult male rats

Calcium (Ca) is necessary for bone calcification, and Ca deficiency leads to decreased bone mineral density (BMD). Epidemiological studies have reported a correlation between Ca intake and BMD. Although the influences of Ca deficiency on BMD have been reported, the effects of Ca restriction on bone during high-fat diet ingestion remain unclear. Therefore, we hypothesized that high-fat diet ingestion would potentiate the negative effects of Ca restriction on bone. Sprague-Dawley strain male rats (aged 11 weeks) were divided into 4 groups: basic control diet (Cont.) (11% lipid energy rate, 0.5% calcium), basic control diet with Ca restriction (CaR) (11% lipid energy rate, 0.02% calcium), high-fat diet (HF) (40% lipid energy rate, 0.5% calcium), and high-fat diet with Ca restriction (HFCaR) (40% lipid energy rate, 0.02% calcium). At 28 days after starting the experimental diets, body weights were higher in the high-fat diet groups (HF and HFCaR) than in the standard-fat diet groups (Cont. and CaR) on 2-way analysis of variance. The apparent Ca absorption rate in the Ca-restricted groups (CaR and HFCaR) was higher than in the Ca-sufficient groups (Cont. and HF). BMD and bone strength parameters of the femur and lumbar vertebrae in the Ca-restricted groups were markedly lower than in the Ca-sufficient groups, whereas there were no significant differences between the standard-fat diet and HF diet groups. These results suggest that 28 days of Ca restriction increases the risk of bone fracture and osteoporosis. We examined the influences of Ca restriction and/or a high-fat diet on BMD. The apparent Ca absorption rate was significantly higher in the CaR and HFCaR groups compared with the Cont. and HF groups. BMD values of the femur or lumbar vertebrae were markedly lower in the CaR and HFCaR groups compared with the Cont and HF groups. There was no significant difference in BMD between the standard- and high-fat diet groups. Twenty-eight days of Ca restriction increases the risks of bone fracture and osteoporosis regardless of the high-fat diet. Different letters indicate significant differences (P < .05). Abbreviations: BMD, bone mineral density; Ca, calcium; Cont, basic control diet (standard fat and Ca sufficient); CaR, basic control diet with Ca restriction (standard fat); HF, high-fat diet (Ca sufficient); HFCaR, high-fat diet with Ca restriction. [Display omitted]