Vitamin D is actually a family of related essential compounds, referred to as vitamins D-1, D-2, and D-3. Vitamin D is required for the proper regulation and absorption of the essential minerals calcium and phosphorus. Available primarily from animal sources, vitamin D is also commonly called the sunshine vitamin because of the body’s unique ability to synthesize Vitamin-D from brief but regular exposure to sunlight.
Adequate levels of Vitamin D are required for the proper absorption of calcium and phosphorus in the small intestines. Vitamin D further supports and regulates the use of these minerals for the growth and development of the bones and teeth. Because of this vital link, adequate intake of Vitamin D is critically important for the proper mineralization of bones and teeth in developing children. Vitamin D also aids in the prevention and treatment of osteoporosis, osteomalacia, and hypocalcemia in adults.
A prolonged Vitamin D deficiency may result in rickets, an early childhood bone disease that can produce such conditions as bowlegs and knock-knees. Common early symptoms of rickets include restlessness, profuse sweating, poor muscle tone, delayed tooth formation, and impaired development of basic motor skills such as crawling and walking. Rickets is a relatively rare disease due to the modern practice off supplementing dairy foods, such as milk, with vitamin D-2.
Osteomalacia, the adult version of vitamin D deficiency disease, can resemble osteoporosis, a bone condition characterized by an increased tendency of the bones to fracture. One important difference between these two diseases is that osteomalacia is easily treated with vitamin D supplements.
Common food sources of vitamin-D include Fish liver oil, sardines, tuna, salmon, liver, and eggs. Vitamin D is also available in its supplement or food form, as vitamin D-2, called ergocalciferol, and as vitamin D-3, or cholecalciferol. Ultra violet rays acting directly upon the skin can synthesis vitamin D, so exposure to sunlight 2 to 4 times per week is usually an effective way to for assure adequate levels of Vitamin D. This process can be limited for those who live in high-smog areas, who wear sun blocking agents, or by those with naturally dark or tanned skin.
The current Recommended Daily Allowance of Vitamin-D is 400 iu, or international units per day. Common current supplemental doses of Vitamin D range from 400 to 1,000 iu per day, and are extremely safe at this level.
High levels of vitamin D can be toxic. Children begin to show toxic effects when dosages exceed 1,800 iu per day. Adults can show toxic effects with dosages ranging from 10,000 to 20,000 iu per day over extended periods. Symptoms of vitamin D toxicity can include weakness, loss of appetite, unusual thirst, nausea, vomiting, high blood pressure, and elevated calcium levels in the blood. Toxic effects are easily corrected by simply cutting back on the daily intake of vitamin-D. Prolonged exposure to sunlight, while unsafe for other reasons, cannot lead to vitamin D toxicity.
VITAMIN D AS AN ADJUVANT FOR CANCER TREATMENT: There is increasing evidence that vitamin D and its analogs help to prevent and treat several forms of cancer. In a study in the Feb 1994 issue of Research Communications in Chemical Pathology and Pharmacology, vitamin D-3 analogs were less toxic and more effective than fish oil derived vitamin D in normalizing malignant Iymphoma and leukemia cell lines. In the April 1, 1994 issue of Cancer Research, vitamin D analogs effectively prevented and treated breast cancer in rats, significantly enhancing the ability of tamoxifen to render the rats tumor free by the end of the experiment. In the Feb 1994 issue of Leukemia, vitamin D-3 significantly enhanced the effect of Bryostatin 5 in treating human leukemia cell lines. In the Feb. 1994 issue of Pathologie Biologie, vitamin D analogs were shown to be important in regulating the immune system by enhancing immune function against cancer cells and infectious agents, and by preventing autoimmune diseases such as lupus and diabetes.
In a study from The Netherlands in the Feb 1994 issue of Breast Cancer Research and Development, relatively low doses of vitamin D analogs combined with tamoxifen produced “potent inhibition of breast cancer cell proliferation…and indicated a benefit of combining these agents as a treatment for breast cancer.”
Some of these vitamin D analogs are available in Europe and are slowly being accepted by oncologists in the United States as effective adjuvants to conventional cancer therapy. The advantage of using vitamin D analogs is that they do not cause the body to absorb too much calcium, which is one of the toxic effects of ingesting too much vitamin D. For breast and prostate cancer patients, researchers often suggest adding about 3,000 IU of vitamin D-3 based upon the latest findings.