De zon, vitamine D goed voor u*
Uit verschillende studies blijkt dat regelmatig in de zon heel goed voor u is, dat is goed voor voldoende
vitamine D in uw lichaam en dat is weer goed tegen hart- en vaatziekten en gezonde botten.
Uit een gecombineerde Amerikaanse-Deense studie blijkt dat de voordelen van het regelmatig in de zon zijn vele malen groter zijn dan de kans op huidkanker. Zeker mensen in
Midden- en Noord Europa omdat daar al minder zon is. Mensen net onder de evenaar in Australië produceren met eenzelfde tijd in de zon
wel 3,4 keer meer vitamine D dan mensen hier in Nederland en wel 4,8 keer meer als mensen in de Scandinavische landen. Daarom komt in landen rond de evenaar kanker ook veel minder voor en sterven ook aanzienlijk minder mensen aan darm-, long-, borst- en prostaatkanker.
Uit een Amerikaanse studie onder ruim 1.700 mensen van gemiddeld 59 jaar blijkt dat mensen met lage bloedwaarden vitamine D wel 60% meer kans hebben op het krijgen van problemen met hart en bloedvaten zoals een hartaanval, hartfalen of een beroerte als mensen met hoge vitamine D waarden. Slechts 10% van de mensen hadden bloedwaarden vitamine D van 30 ng/ml of hoger. Terwijl toch 30 ng/ml al voor goede botopbouw van belang is. 37% van de mensen had waarden lager dan 15 ng/ml.
-Low blood levels of vitamin D linked to heart attacks and strokes
The same vitamin D deficiency that can result in weak bones now has been associated with an increased risk of cardiovascular disease, Framingham Heart Study researchers report in Circulation: Journal of the American Heart Association.
"Vitamin D deficiency is associated with increased cardiovascular risk, above and beyond established cardiovascular risk factors," said Thomas J. Wang, M.D., assistant professor of medicine at Harvard Medical School in Boston, Mass. "The higher risk associated with vitamin D deficiency was particularly evident among individuals with high blood
pressure."
In a study of 1,739 offspring from Framingham Heart Study participants (average age 59, all Caucasian), researchers found that those with blood levels of vitamin D below15 nanograms per milliliter (ng/mL) had twice the risk of a cardiovascular event such as a heart attack, heart failure or stroke in the next five years compared to those with higher levels of vitamin D.
When researchers adjusted for traditional cardiovascular risk factors such as high cholesterol, diabetes and high blood pressure, the risk remained significant with a 62 percent higher risk of a cardiovascular event in participants with low levels of vitamin D compared to those with higher levels.
Researchers observed the highest rate of cardiovascular disease events in subset analyses dividing 688 participants according to high blood pressure status. After researchers adjusted for conventional cardiovascular risk factors, participants with hypertension and a vitamin D deficiency had about 2 times the risk of having a cardiovascular disease event in five years.
Researchers also found an increase in cardiovascular risk with each level of vitamin D
deficiency.
"We found that people with low vitamin D levels had a higher rate of cardiovascular events over the five-year follow-up period," Wang said. "These results are intriguing and suggestive but need to be followed up with further study."
Study participants had no prior cardiovascular disease and were tested for vitamin D status and then followed for an average of 5.4
years.
The participants attended the offspring examinations between 1996 and 2001. Researchers obtained medical history, physical examinations and laboratory assessments of vascular risk factors. They also obtained medical records related to cardiovascular
disease.
Overall, 28 percent of individuals had levels of vitamin D below15 ng/mL and 9 percent had levels below10 ng/mL. Although levels above 30 ng/mL are considered optimal for bone metabolism, only 10 percent of the study sample had levels in this range, researchers said.
During follow-up:
* 120 participants developed a first cardiovascular event including fatal and nonfatal coronary heart
disease;
* 28 participants had fatal or nonfatal cerebrovascular events such as nonhemorrhagic
stroke;
* 19 participants were diagnosed with heart failure; and
* 8 had occurrences of claudication, fatigue in the legs during activity.
"Low levels of vitamin D are highly prevalent in the United States, especially in areas without much sunshine," Wang said. "Twenty to 30 percent of the population in many areas has moderate to severe vitamin D
deficiency."
Most of this is attributed to lack of sun exposure, pigmented skin that prevents penetration of the sun's rays and inadequate dietary intake of vitamin D enriched foods, researchers
said.
"A growing body of evidence suggests that low levels of vitamin D may adversely affect the cardiovascular system," Wang said. "Vitamin D receptors have a broad tissue distribution that includes vascular smooth muscle and endothelium, the inner lining of the body's vessels. Our data raise the possibility that treating vitamin D deficiency, via supplementation or lifestyle measures, could reduce cardiovascular risk.
"What hasn't been proven yet is that vitamin D deficiency actually causes increased risk of cardiovascular disease. This would require a large randomized trial to show whether correcting the vitamin D deficiency would result in a reduction in cardiovascular risk."
Therfore, Wang doesn't recommend physicians check for vitamin D deficiency or that those with a known vitamin D deficiency be treated to prevent heart disease at this time.
During the past decade, researchers have studied several other vitamins that initially showed promise in reducing heart disease. But the vitamins didn't reduce heart disease in subsequent large randomized trials.
"On the flip side, just because other vitamins haven't succeeded doesn't preclude the possibility of finding vitamins that might prevent cardiovascular disease," Wang said. "This is always an area of great interest. Vitamins are easy to administer and in general have few toxic
effects."
The American Heart Association recommends that healthy people get adequate nutrients by eating a variety of foods in moderation, rather than by taking supplements. Food sources of vitamin D include milk, salmon, mackerel, sardines, cod liver oil and some fortified cereals. Vitamin or mineral supplements aren't a substitute for a balanced, nutritious diet that limits excess calories, saturated fat, trans fat, sodium and dietary cholesterol. This dietary approach has been shown to reduce coronary heart disease risk in healthy people and those with coronary disease.
-Researchers say health benefits of sunshine outweigh the skin cancer risk and might help you live longer
According to a new study sunshine might help you live longer and for some people the health benefits possibly outweigh the skin cancer risk of skin cancer.
Researchers are suggesting that because people have become frightened of getting skin cancers they are avoiding the sunshine, but sunshine offers one of the best sources of vitamin D which protects the body from a number of diseases.
Sunlight stimulates the body to produce vitamin D which has been proven to offer protection from some cancers, osteoporosis, rickets and diabetes.
The scientists at the U.S. Department of Energy's Brookhaven National Laboratory and colleagues at Norway's Institute for Cancer Research in Oslo, say the health benefits from some sun exposure are far larger than the skin cancer risk.
Lead researcher Johan Moan says modest sun exposure gives enormous vitamin D benefits and though certain foods contain vitamin D, the body's main source is from the sun.
The researchers have worked out that given the same amount of time spent outside, people living just below the equator in Australia produced 3.4 times more vitamin D than people in Britain and 4.8 times more than Scandinavians.
They say even though rates of internal cancers such as colon cancer, lung cancer, breast cancer and prostate cancer are greater in the north than the south, people from the southern latitudes were significantly less likely to die from these internal cancers than people in the north.
Richard Setlow of the U.S. Department of Energy's Brookhaven National Laboratory, who worked on the study says current data provides a more information on the beneficial role of sun-induced vitamin D for cancer prognosis.
Setlow says although increased UVB exposure may result in an increase in non-melanoma skin cancers these are relatively easy to cure and have very low mortality rates compared with the internal cancers vitamin D appears to protect against.
Moan says for people living in countries such as Scandinavia where long winters and short days during the year limit exposure to the sun getting more vitamin D is critical to help the body's immune system work properly.
Moan has estimated that doubling the sun exposure for the general population in Norway would also double the number of annual skin cancer deaths to about 300 but that 3,000 fewer people would die from other cancers and he believes the benefits could also be significant for people in other countries.
Moan recommends daily sun exposure for about half the time it takes a person to get sunburn; another way to access more vitamin D could be by designing sunscreens which block the long ultraviolet wavelengths that trigger the deadliest forms of skin cancer while letting through short ultraviolet wavelengths that produce the vitamin.
Vitamin D is present in many foods such as cod liver oil and milk, and in can also be taken as a dietary supplement.
The study is published in the Proceedings of the National Academy of Sciences. (Februari
2008)
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