Nutrition Lecture 7: Calcium Flashcards
What are rich sources of dairy?
Dairy products, fortified alternatives, tofu, leafy greens (kale), almonds
What happens to the bioavailability of calcium over a lifetime?
Decreases with age
What is the bioavailability of calcium from dairy products?
30%
What is the bioavailability of calcium from fortified soy milk?
20-30%
What is the bioavailability of calcium from kale?
40%
When does bioavailability of calcium decrease?
may be poorly absorbed from foods rich in oxalic acid or phytate
What foods are rich in oxalic acid?
spinach, rhubarb
What foods are rich in phytate?
Seeds, nuts, wholegrains
What is the absorption of calcium from supplements?
30%
At higher does what happens to calcium absorption?
absorption reduces at higher doses (>500mg) increases when consumed with a meal
What is VDR?
Vitamin D receptor
What are the two mechanisms for calcium to cross the intestinal mucosa?
- Absorbed by active transport (transcellular)
- Passive diffusion (paracellular)
What does active transport of calcium require?
Vitamin D
When does the passive diffusion of calcium become increasingly important?
as Ca intakes increase
How tightly is calcium homeostasis controlled?
Levels of circulating Ca must be within a narrow physiological range for body to function normally
What is the serum calcium physiological range?
2.12-2.62
How are serum calcium levels maintained?
Through an endocrine system with strict controlling factors and feedback mechanisms
What molecules play key roles in maintaining Ca homeostasis?
Vitamin D (calcitriol) and parathyroid hormone (PTH)