All these years, you thought it was just another vitamin.
Used to treat rickets nearly a century ago, vitamin D has seen its stock rise in recent years with waves of research suggesting it's an indispensable dietary dynamism whose daily dose delivers dramatic results.
D is becoming vitamin deity.
Actually it's not a vitamin. The fat-based seco-steroid hormone that skin produces with sun exposure has shown a long list of benefits.
The Vitamin D Council, a nonprofit organization in Atascadero, Calif., led by Dr. John J. Cannell, links about 65 diseases, conditions or health problems to a vitamin D deficiency.
Lack of vitamin D is a major factor in the pathology of at least 17 varieties of cancers including breast and prostate cancers, heart disease, stroke, hypertension, autoimmune disease, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects and periodontal disease, the council states.
"In humans, vitamin D is critically important for the development, growth and maintenance of a healthy body, from birth until death," the council says on its Web site, www.vitamindcouncil.org.
It suggests 50 to 80 nanograms per milliliter of vitamin D in the blood year round. Dr. Cannell said people who do not get regular daily sun exposure need 5,000 international units a day of vitamin D -- more than 12 times the current recommended 400 IU daily allowance. Those amounts can be achieved with a conservative regimen of sun exposure.
"The older the skin the less effective and efficient the skin is in making vitamin D," he said. "If you are 70, you have to stay out in the sun twice as long as someone who is 30 to produce the same amount of vitamin D."
He said people rightfully are jaded by claims of health benefits from vitamins. "Many do not turn out to be true, so they hear about vitamin D and they will not fall for it again," Dr. Cannell said.
But volumes of research are proving vitamin D's importance.
Natural production of vitamin D3 cholecalciferol in the skin "is the single most important fact every person should know about vitamin D -- a fact that has profound implications for the natural human condition," the Vitamin D Council states.
Lack of sunlight exposure and declining nutrition in the American diet has produced a vitamin D deficiency throughout the population.
Nowadays some nutritionists have bumped up the daily dose to 1,000 IU and, if Dr. Cannell's recommendations are any indication, significantly higher. An overdose of vitamin D can be toxic, even deadly. But Dr. Cannell said even 5,000 IUs a day are safe for days when the person receives no sun exposure.
Dr. Betsy Blazek-O'Neill, medical director of Allegheny General Hospital's Integrated Medicine Program, said the problem is the lack of food sources containing vitamin D. "There is some in fish and dietary sources, but the main source is sunshine," she said.
Dr. Blazek-O'Neill said a precursor chemical in the skin when exposed to sunshine changes into vitamin D, and "that's why it is known as the sunshine vitamin."
Twenty minutes of sunshine each day on the face, parts of the arms and chest should provide sufficient vitamin D.
"There are a whole bunch of studies that show that people who are low in vitamin D suffer from depression, skin cancer and heart problems, but there are not good studies that show whether the supplement can reverse those problems," Dr. Blazek-O'Neill said. "But people over 50 who took vitamin D seemed to have a lower mortality than those who didn't take it as a supplement."
She said it also has a major impact on mental health, including mood and depression and even chronic pain: "People with chronic pain are more likely to be low in D," she said. "When they get normal levels of vitamin D, some do better."
Roger Mason of www.youngagain.org said the nation is experiencing "an epidemic deficiency" of vitamin D but said a daily dose of 800 IUs is sufficient. Cod liver oil has been an important supplement throughout the decades because it's high in vitamin D.
While most people are deficient in D, the poor and elderly are most susceptible.
"The science behind this is just overwhelming," states an article Mr. Mason wrote about vitamin D. "People of all ages should take it. The internationally published science is endless and growing."
Dr. Blazek-O'Neill and Dr. Cannell recommend that people be tested for vitamin D levels in their blood before a vitamin regimen is prescribed. But Dr. Cannell said to make sure patients specifically get the "25 hydroxycholecalciferol vitamin D test." Another test -- 1,25 dihydroxycholecalciferol vitamin D test -- is done to gauge the impact of renal failure. Dr. Cannell said doctors sometimes confuse the two.
But research on the benefits of vitamin D has become so pervasive that even mainstream physicians have begun recommending supplements for patients.
There are various types of D, including D1, D2 and D3. The first two are precursors in the skin, while D3 can be taken orally.
"There's definitely value in it," Dr. Blazek-O'Neill said. "In the popular press, you have to wonder if the claims are exaggerated. We'll have to see what the research is on that."
Vitamin D is but one vitamin deficiency the aging population can experience. Recommended dietary allowances for heart health include B12, which people over 50 have a reduced ability to absorb. To get the recommended daily allowance of 2.4 micrograms per day of B12, people should eat fortified cereals and other foods or take the crystalline form of vitamin B12 supplements.