What inhibits calcium absorption?

Medications, such as corticosteroids, proton pump inhibitors, tetracycline and thyroid hormones can inhibit calcium absorption. Smoking, lack of exercise and stress also affect the body's ability to absorb calcium. Iron supplements can also interfere with iron absorption, and vitamin D deficiency lowers the body's ability to absorb calcium.

Substances in some foods can inhibit calcium absorption. Excess protein, sodium, insoluble fiber and caffeine are a few culprits. Oxalates, found in spinach, beet greens, rhubarb, chocolate and berries, bind with calcium, causing excretion of calcium via the feces. Phosphorus, found in many colas and processed foods, also inhibits calcium absorption. Excessive alcohol intake is also known to upset the balance of calcium in the body.