Sunday, October 11, 2009

More about Vitamin D

This is straight from Wikipedia:

Role in cancer prevention and recovery

The vitamin D hormone, calcitriol, has been found to induce death of cancer cells in vitro and in vivo. The anti-cancer activity of vitamin D is thought to result from its role as a nuclear transcription factor that regulates cell growth, differentiation, apoptosis and a wide range of cellular mechanisms central to the development of cancer.[65] These effects may be mediated through vitamin D receptors expressed in cancer cells.[14]
A search of primary and review medical literature published between 1970 and 2007 found an increasing body of research supporting the hypothesis that the active form of vitamin D has significant, protective effects against the development of cancer. Epidemiological studies show an inverse association between sun exposure, serum levels of 25(OH)D, and intakes of vitamin D and risk of developing and/or surviving cancer. In 2005, scientists released a metastudy which demonstrated a beneficial correlation between vitamin D intake and prevention of cancer. Drawing from a meta-analysis of 63 published reports, the authors showed that intake of an additional 1,000 international units (IU) (or 25 micrograms) of vitamin D daily reduced an individual's colon cancer risk by 50%, and breast and ovarian cancer risks by 30%.[66][67][68] A scientific review undertaken by the National Cancer Institute found that vitamin D was beneficial in preventing colorectal cancer, which showed an inverse relationship with blood levels of 80 nmol/L or higher associated with a 72% risk reduction. However, the same study found no link between baseline vitamin D status and overall cancer mortality.[69]
A 2006 study using data on over 4 million cancer patients from 13 different countries showed a marked difference in cancer risk between countries classified as sunny and countries classified as less–sunny for a number of different cancers.[70] Research has also suggested that cancer patients who have surgery or treatment in the summer — and therefore make more endogenous vitamin D — have a better chance of surviving their cancer than those who undergo treatment in the winter when they are exposed to less sunlight.[71] Another 2006 study found that taking the U.S. RDA of vitamin D (400 IU per day) cut the risk of pancreatic cancer by 43% in a sample of more than 120,000 people from two long-term health surveys.[72][73] A randomized intervention study involving 1,200 women, published in June 2007, reports that vitamin D supplementation (1,100 international units (IU)/day) resulted in a 60% reduction in cancer incidence, during a four-year clinical trial, rising to a 77% reduction for cancers diagnosed after the first year (and therefore excluding those cancers more likely to have originated prior to the vitamin D intervention).[74][75] Research has also indicated beneficial effects of high levels of calcitriol on patients with advanced prostate cancer.[76]
Low levels of vitamin D in serum have also been correlated with breast cancer disease progression and bone metastases,[77] and studies suggest that increased intake of vitamin D reduces the risk of breast cancer in premenopausal women.[78] Polymorphisms of the vitamin D receptor (VDR) gene have been associated with an increased risk of breast cancer.[77] Impairment of the VDR-mediated gene expression is thought to alter mammary gland development or function and may predispose cells to malignant transformation. Women with homozygous FOK1 mutations in the VDR gene had an increased risk of breast cancer compared with the women who did not. FOK1 mutation has also been associated with decreasing bone mineral density which in turn may be associated with an increase in the risk of breast cancer.[79]
[edit]Role in cardiovascular disease prevention

Research indicates that vitamin D may play a role in preventing or reversing coronary disease.[80][81] Vitamin D deficiency is associated with an increase in high blood pressure and cardiovascular risk. When researchers monitored the vitamin D levels, blood pressure and other cardiovascular risk factors of 1739 people, of an average age of 59 years for 5 years, they found that those people with low levels of vitamin D had a 62% higher risk of a cardiovascular event than those with normal vitamin D levels.[82] Low levels of vitamin D have also been implicated in hypertension, elevated VLDL triglycerides, and impaired insulin metabolism.[83]
A report from the National Health and Nutrition Examination Survey (NHANES) involving nearly 5,000 participants found that low levels of vitamin D were associated with an increased risk of peripheral artery disease (PAD). The incidence of PAD was 80% higher in participants with the lowest vitamin D levels (<17.8 ng/mL).[39] Cholesterol levels were found to be reduced in gardeners in the UK during the summer months.[84] Heart attacks peak in winter and decline in summer in temperate[85] but not tropical latitudes.[86]
The issue of vitamin D in heart health has not yet been settled. Exercise may account for some of the benefit attributed to vitamin D, since vitamin D levels are generally higher in physically active persons.[87] Moreover, there may be an upper limit after which cardiac benefits decline. One study found an elevated risk of ischaemic heart disease in Southern India in individuals whose vitamin D levels were above 89 ng/mL.[52] These sun-living groups results do not generalize to sun-deprived urban dwellers. Among a group with heavy sun exposure, taking supplemental vitamin D is unlikely to result in blood levels over the ideal range, while urban dwellers not taking supplemental vitamin D may fall under the levels recognized as ideal.
[edit]Role in all-cause mortality

Using information from the National Health and Nutrition Examination Survey a group of researchers concluded that having low levels of vitamin D (<17.8 ng/mL) was independently associated with an increase in all-cause mortality in the general population.[88] The study evaluated whether low serum vitamin D levels were associated all-cause mortality, cancer, and cardiovascular disease (CVD) mortality among 13,331 diverse American adults who were 20 years or older. Vitamin D levels of these participants were collected over a 6-year period (from 1988 through 1994), and individuals were passively followed for mortality through the year 2000.
Among many factors that may be responsible for vitamin D's apparent beneficial effect on all-cause mortality is its effect on telomeres and its potential effect on slowing aging. Shortening of leukocyte telomeres is a marker of aging. Leukocyte telomere length (LTL) predicts the development of aging-related disease, and length of these telomeres decreases with each cell division and with increased inflammation (more common in the elderly) Research indicates that vitamin D is a potent inhibitor of the proinflammatory response and slows the turnover of leukocytes. Higher vitamin D levels were also associated with longer leukocyte telomere length, indicating that vitamin D sufficiency may be play a role in preventing age-related diseases.[89]

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