Trying to shine some light on the importance of vitamin D or lack of it.
Low Levels can cause serious illness, but no major tests have been run
By Jane E. Brody
as published in the Jakarta Post Wednesday 14 March 2012
Although there are still no large trials to prove or disapprove the full worth of vitamin D, studies have linked lower levels of it to risk of hearth disease, high blood pressure, cancer, rheumatoid arthritis.
Often, though the concern is bone health. Without vitamin D, the body can not properly absorb calcium and bone can become fragile. At the annual meeting of the American Academy of Orthopaedic Surgeons last month, researchers reported that among 889 adult patients treated for a fracture at a Missouri trauma center , blood level were “insufficient” in 78 percent and “frankly deficient” in 39 percent. The study group excluded those with known risk factors for vitamin D deficiency.
And a report by doctors in Soul found vitamin D levels were “significantly lower” among postmenopausal women who had broken wrist than among 107 age-matched control without a fracture.
Meantime, many studies in recent years have linked low levels of vitamin D to health risks like heart diseases, high blood pressure, cancer, rheumatoid arthritis and other autoimmune disease, prompting many health-conscious men and women to think supplements of vitamin D are protective.
Alas, there are still no large-scale randomized controlled clinical trials to prove or disapprove the value of vitamin D supplementation.
But Kevin Fiscella, a public health specialist and family physician at the University of Rochester in New York, has decided to take 1000 international units of vitamin D each day, based on data from his studies linking radical disparities in vitamin D levels to diseases risk and his belief that “it can’t hurt and it may help”
In an interview, Dr. Fiscella emphasized that his findings strongly suggest, but do not prove, that vitamin D deficiencies cause or contribute to diseases like colorectral cancer, high blood pressure and kidney and heart diseases, which affect black Americans at higher rates than whites. The findings are bolstered by known biological effects of vitamin D and the fact that widespread vitamin D deficiencies occurs among black living in the Northern Hemisphere.
Nearly every body tissue has receptors for vitamin D, among them the intestines, brain, heart,sex organs, breasts and lymphocytes, as well as the placenta. The vitamin, which acts as a hormone, is known to influence the expression of more than 200 genes.
In lab studies, it has been shown to have anticancer activity , inhibiting the growth and spread tumors. There is also suggestive but inconclusive evidence that vitamin D deficiency plays a role in asthma, Type 2 diabetes, autoimmune diseases like multiple sclerosis and rheumatoid arthritis, pre-eclampsia and low birth weight, and disorder like depression, autism and memory loss.
Very few foods naturally contains meaningful levels of vitamin D: mostly they are fatty cold-water fish like salmon, mackerel, bluefish, anchovies, sardines and tuna, as well as cod liver oil. Some foods are fortified with it: milk, instant formula, and some brand of orange juice, yoghurt, cheese and breakfast cereal.
Several factors work against achieving the levels of vitamin D known to prevent bone loss, let alone other diseases should a cause-and-effect ever be established.
One is the skin color. Dark skin evolved in equatorial Africa, where the sun is intense year round and just a brief daily exposure to UVB (the sun’s burning rays) is sufficient to achieve adequate blood levels of vitamin D. But melanin in the skin acts as a natural sunblock, and among blacks living in the United States, where sun is less intense, less of the previtamin is produced.
Dr.Fiscella studies, based on thousands of adult participants in the National Health and Nutrition Examination Survey conducted from 2001-2006, revealed much higher rates vitamin D deficiency among non-Hispanic blacks than non-Hispanic whites. In separates studies, lower levels of vitamin D among blacks across the United States were assoiciated with a greater incidence of colorectral cancer, high blood pressure, protein in urine ( a precursor of kidney disease) and cardiovascular deaths.
Warnings about the cosmetic and cancerous consequences of sun exposure have prompted millions of health-conscious people to protect themselves from UVB with protective clothing and liberal use of sunscreen on exposed skin. The latter can reduce previtamin D production in skin more than 90 percent.
Meanwhile, the Endoctrine Society recommends that people at risk for vitamin D deficiency be screened to determine their serum levels. People taking drugs like anticonvultants, glucocorticoids, antiretrovirals, antifungals and cholestyramine also should be tested.
And Dr. Fiscella said certain groups at risk for a deficiency also warrant screening: blacks, obese children and adults, and pregnant or nursing women