The so-called sunshine vitamin is poised to become the nutrient of the decade, if a host of recent findings are to be believed. Vitamin D, an essential nutrient found in a limited number of food, has long been renowned for its role in creating strong bones, which is why it is added to milk.
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Now, a growing legion of medical researchers has raised strong doubts about the adequacy of currently recommended levels of intake, from birth through the sunset years. The researchers maintain, based on a plethora of studies, that vitamin D levels considered adequate to prevent bone malformations like rickets in children are not optimal to counter a host of serious ailments that are now linked to low vitamin D levels.
To be sure, not all medical experts are convinced of the need for or the desirability of raising the amount of vitamin D people should receive, either through sunlight, food, supplements, or all three. The federal committee that establishes daily recommended levels of nutrients has resisted all efforts to increase vitamin D intake significantly, partly because the members are not convinced of assertions for its health-promoting potential and partly because of time-worn fears of toxicity.
MYRIAD LINKS TO HEALTH
* Strong bones. Last year, a 15-member team of nutrition experts noted in The American Journal of Clinical Nutrition that "randomized trials using the currently recommended intakes of 400 IU vitamin D a day have shown no appreciable reduction in fracture risk."
"In contrast," the experts continued, "trials using 700 to 800 IU found less fracture incidence, with and without supplemental calcium. This change may result from both improved bone health and reduction in falls due to greater muscle strength."
A Swiss study of women in their 80s found greater leg strength and half as many falls among those who took 800 Hi of vitamin D a day for three months along with 1,200 milligrams of calcium, compared with women who took just calcium. Greater strength and better balance have been found in older people with high blood levels of vitamin D.
* Reduced tumor risk. In animal studies, vitamin D has strikingly reduced tumor growth, and a large number of observational studies in people have linked low vitamin D levels to an increased risk of cancer, including cancers of the breast, rectum, ovary, prwostate, stomach, bladder, esophagus, kidney, lung, pancreas, and uterus, as well as Hodgkin's lymphoma and multiple myeloma.
Researchers at Creighton University in Omaha reported last year in The American Journal of Clinical Nutrition that over the course of four years, those taking calcium and 1,100 IU of vitamin D3 each day developed about 80 percent fewer cancers than those who took just calcium or a placebo.
* The immune system. Vitamin D seems to dampen an overactive immune system. The incidence of autoimmune diseases like Type 1 diabetes and multiple sclerosis has been linked to low levels of vitamin D. A study published Dec. 20, 2006, in The Journal of the American Medical Association, examined the risk of developing multiple sclerosis among more than 7 million military recruits followed for up to 12 years. Among whites, but not blacks or Hispanics, the risk of developing MS increased with ever lower levels of vitamin D in their blood serum before age 20.
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Vitamin D is a fat-soluble vitamin that when consumed or made in the skin can be stored in body fat. In summer, as little as five minutes of sun a day on unprotected hands and face can replete the body's supply. Any excess can be stored for later use. But for most people during the rest of the year, the body needs dietary help.
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A study published in Neurology in 2004 found a 40 percent lower risk of MS in women who took at least 400 IU of vitamin D a day.
* Diabetes. A study of a national sample of non-Hispanic whites found a 75 percent lower risk of diabetes among those with the highest blood levels of vitamin D.
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WHERE TO OBTAIN IT
* Sunlight: the primary source of vitamin D, which is formed in skin exposed to ultraviolet B radiation (the UV light that causes sunburns).
* Fortified drinks like milk, soy milk, and some juices
* Oily fish like salmon, mackerel, bluefish, catfish, sardines, and tuna
* Cod liver oil and fish oils
* The amount of vitamin D in breakfast cereals is minimal at best.
* As for supplements, vitamin D is found in prenatal vitamins, multivitamins, calcium-vitamin D combinations, and plain vitamin D. Check the label, and select brands that contain vitamin D3, or cholecalciferol. D2, or ergocalciferol, is 25 percent less effective.
HOW MUCH
Vitamin D content is listed on labels in international units (IU). An 8-ounce glass of milk or fortified orange juice is supposed to contain 100 IU. Most brands of multivitamins provide 400 a day. Half a cup of canned red salmon has about 940, and 3 ounces of cooked catfish about 570.
As for a maximum safe dose, researchers like Bruce W. Hollis, a pediatric nutritionist at the Medical University of South Carolina in Charleston, maintain that the current top level of 2,000 RI is based on shaky evidence. Hollis has been giving pregnant women 4,000 RI a day, and nursing women 6,000, with no adverse effects. Other experts, however, are concerned that high vitamin D levels (above 800 RI) with calcium can raise the risk of kidney stones in susceptible people.
* To determine how much vitamin D is needed from food and supplements, take into account factors like skin color, where you live, time of year, time spent out of doors, use of sunscreens and cover-ups, and age.
* Sun avoiders and dark-skinned people absorb less UV radiation. People in the northern two- thirds of the country make little or no vitamin D in winter, and older people make less vitamin D in their skin and are less able to convert it into the hormone that the body uses.
* Babies fed just breast milk consume little vitamin D unless given a supplement.
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Source: Manila Bulletin
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