Final answer:
Postmenopausal women like Sarah need to take vitamin D along with calcium to ensure efficient absorption of calcium from the intestine, which is vital for maintaining bone health and preventing osteoporosis.
Step-by-step explanation:
Sarah, who is postmenopausal, needs to take vitamin D along with her 1500 mg of calcium because vitamin D is essential for the intestinal absorption of calcium. Without adequate levels of vitamin D, the calcium consumed cannot be efficiently absorbed from the small intestine into the bloodstream, which can lead to brittle and weak bones and an increased risk of osteoporosis.
Vitamin D is crucial not only for calcium absorption but also for bone remodeling, which is a continuous process where new bone tissue replaces the old tissue. This helps maintain bone strength and health. After menopause, women experience a natural decline in estrogen, which is involved in calcium metabolism, leading to decreased blood calcium levels and the potential loss of bone density. Therefore, supplementing with vitamin D can help mitigate the risks associated with postmenopausal calcium deficiency and osteoporosis.