Deficiencies of calcium and vitamin D are thought to increase the risk of certain cancers, such as cancer of the colon. Excess calcium has been linked to an increase in prostate cancer. Calcium is also important in the prevention and treatment of osteoporosis.
Forty percent of calcium in the blood is bound to a large protein in the blood called albumin. Ten percent is bound to other substances. The remainder is free in the blood.
Calcium is regulated by parathyroid hormone (PTH), which is secreted by the parathyroid glands. Parathyroid hormone causes a release of calcium from the bone, increased absorption of calcium in the intestines, and it prevents calcium loss through the kidneys. All of this is in response to low blood calcium levels.
Calcitonin is secreted by the thyroid gland in response to high blood calcium levels. It has the effect of decreasing the release of calcium from the bone and it inhibits parathyroid hormone release.
Calcium is an important nutrient since it can bind free fatty acids, bile acids, and unconjugated bile in the intestine. This is the natural way for excretion of toxins from the body. Calcium plays an important role in this process.
Calcium has been shown some to exert a weak to moderate degree of protection from colon cancer. High levels, however, have been shown to increase the risk of prostate cancer. Dietary intake of 500 to 600 milligrams seems to increase the risk of cancer. Most of the calcium in the American diet is from milk and diary products, which is a highly absorbable form of calcium. The average American consumes about 750 milligrams of calcium per day, where as the intake is recommended to be 1200 to 1500 milligrams a day.
Vitamin D acts more like a hormone than a vitamin. Vitamin D is found in fish and eggs. It is also added to milk and butter. However, most of our Vitamin D is produced in our own bodies with the help of sunlight. Vitamin D has been shown to exert a weakly protective effect against colon cancer. However, milk has been shown to increase the risk for prostate cancer.
Vitamin D comes in several forms, but two will be discussed here. Sunlight produces Vitamin D called 1, 25 (OH 2) D while milk is fortified with Vitamin D called 25 (OH) D. The difference is 1, 25 (OH 2)D only stays around in our system for four to six hours, while 25 (OH) D stays around for about three weeks. Some have speculated that this form of Vitamin D may have too much of a stimulatory effect and might increase the risk of some cancers.
With both calcium and Vitamin D, you should ask your physician about types and doses to fit your lifestyle and health needs.