CALCIUM Calcium is essential for the formation and maintenance of bones and teeth,blood clotting,normal heart beat and hormone secretion DRI:1000 mg ADA.M
3. Absorption and Metabolism 1) Mechanism of absorption: ➢ Position: in the small intestine ➢ Transcellular(跨细胞): saturable(可饱和的) (active) transfer that involves a calcium-biding protein, calbindin (钙结合蛋白). ➢ Paracellular (同细胞水平): a nonsaturable (diffusional 扩散) transfer that is a linear(一维的) function of the calcium content of the chyme(食糜)
3. Absorption and Metabolism 1) Mechanism of absorption: ➢ Position: in the small intestine ➢ Transcellular(跨细胞): saturable(可饱和的) (active) transfer that involves a calcium-biding protein, calbindin (钙结合蛋白). ➢ Paracellular (同细胞水平): a nonsaturable (diffusional 扩散) transfer that is a linear(一维的) function of the calcium content of the chyme(食糜)
Ca, P metabolism
Ca, P metabolism
2) Affecting factors Age ➢children: 75% 0f ingested Ca; >40% of food Ca ➢adults: 30%-60%; 20% ~ ➢> 70y 1/3 of adult’s; < 15% ~ Sex ➢male > female Physiological situation ➢pregnancy and breast-feed > others Body Ca conc
2) Affecting factors Age ➢children: 75% 0f ingested Ca; >40% of food Ca ➢adults: 30%-60%; 20% ~ ➢> 70y 1/3 of adult’s; < 15% ~ Sex ➢male > female Physiological situation ➢pregnancy and breast-feed > others Body Ca conc
Dietary factors ➢ increasing Ca absorption: Vit. D, Lactose, Some amino acids: Arginine(精氨酸), lysine (赖氨酸) ➢ decreasing Ca absorption : phytate(植酸盐), oxalate(草酸盐), fibre, fatty acid, alcohol; thyroid hormone(甲状 腺素), cortisol(皮质醇), and antibiotics: penicillin, chloramphenical (氯霉素), neomycin (新霉素)
Dietary factors ➢ increasing Ca absorption: Vit. D, Lactose, Some amino acids: Arginine(精氨酸), lysine (赖氨酸) ➢ decreasing Ca absorption : phytate(植酸盐), oxalate(草酸盐), fibre, fatty acid, alcohol; thyroid hormone(甲状 腺素), cortisol(皮质醇), and antibiotics: penicillin, chloramphenical (氯霉素), neomycin (新霉素)