by Marcelle Pick, OB/GYN NP
Calcium is one of the most important minerals in the body, not only for bones which store up to 99% but other physiological functions, including nerve transmission, blood clotting, muscle growth and contraction, heart function, hormone function, and metabolism.
Whenever your body needs calcium, it calls upon the bone tissue to release some of its stores into your blood. Your bones comply by upping the rate of resorption (osteoclasts skim off old bone into the blood stream). Whatever doesn’t get used gets excreted through the kidneys—this is why doctors test your urine for calcium as one marker of bone loss. Excessive calcium can cause other difficulties, like kidney stones, gallstones and hypercalcemia.
If your body can’t metabolize calcium properly from your diet because of deficiencies elsewhere it won’t matter how much calcium you eat, your body will take it from your bones. This triggers more osteoblast activity, but bone needs the same nutrients to form—so over time the whole system weakens and affects other body functions.
Even though we have an ample supply of calcium in our diets through dairy products, leafy green vegetables, and seaweed products, many women lack the other minerals necessary for the proper absorption of calcium. A mineral deficiency is usually seen first in non-vital areas like your teeth, hair, and nails.
Vitamin D is crucial to the proper metabolism of calcium, in conjunction with stomach acids and vitamin C. One reason older women have a hard time absorbing calcium is that they lack the digestive acids necessary to break down the mineral.
Magnesium is another mineral that must be present for you to utilize calcium. Magnesium increases calcium absorption form the blood into the bone. Dairy products contain little magnesium and alcohol depletes it. Too much calcium blocks the absorption of magnesium, leading to a deficiency characterized by hair loss, muscle cramps, irritability, trembling, and disorientation.
Trace minerals like boron, selenium, copper, silicon, manganese, and zinc are also important in supporting the healthy balance that makes bone. For an in-depth explanation of all this and more, I encourage you to read Annemarie Colbin’s wonderful book, Food and Our Bones.
Calcium metabolism is dependent on a range of other factors, but I’ll cover only two other substances here: calcitonin and parathyroid hormone—both secreted by the thyroid gland. The former is excreted to stabilize high levels of calcium; the latter is triggered by low levels of calcium, usually characterized by high levels of phosphorous in the blood. Phosphorous is as important to bone strength as calcium, in the right amount. Soda and red meat—two staples of the American diet—are chock full of phosphorous.