Dairy products 2. Canned fish 6. Leafy green vegetables 7. A shortage of calcium causes osteoporosis where the bones become thin and are likely to break easily. Calcium is also needed for muscle contraction, regulation of the heartbeat, and is involved in the process of blood clot formation.
Vitamin D is needed to help calcium get absorbed into the body.
It's made under the skin in response to sunlight and can also be found in foods such as cod liver oil, mackerel, canned salmon, eggs, and milk. The four pea-sized parathyroid glands are responsible for regulating the body's calcium levels. These small glands, which are embedded in the tissue of the thyroid gland, detect fluctuations in the level of calcium in the blood. This causes calcium to be released from the bones, more calcium to be reabsorbed through the kidneys, and more to be absorbed from food in the intestine. If the level of calcium rises too high then PTH secretion is decreased and calcium levels return to normal again.