(Charlotte Ball/PA) (PA Archive)
The researchers said their work, published in Elsevier's European Journal of Cancer, adds to evidence that vitamin D may have a protective effect against cancer. While the findings do not explain why this happens, the team said one possibility is that vitamin D supplements may induce anti-inflammatory, antioxidant, and DNA damage repair mechanisms, which can thwart mutations that allows tumours to grow.
Study author Ben Schottker, an epidemiologist at the German Cancer Research Centre, said: "Our findings identified a statistically significant relationship between vitamin D deficiency and increased mortality among several cancers. "These results can be explained by other studies, which found mechanisms by which vitamin D inhibits cancer growth and metastasis."
The NHS advice is that adults and children over four take a daily supplement containing 10 micrograms of vitamin D throughout the year. According to the Department of Health and Social Care, around one in six adults and almost 20% of children in the UK have vitamin D levels lower than government recommendations....Story continues....
By : Nilima Marshall
Source: Vitamin D intake 'may reduce cancer mortality in the population by 15%' | The Independent
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Critics:
The active vitamin D metabolite calcitriol mediates its biological effects by binding to the vitamin D receptor (VDR), which is principally located in the nuclei of target cells. The binding of calcitriol to the VDR allows the VDR to act as a transcription factor that modulates the gene expression of transport proteins (such as TRPV6 and calbindin), which are involved in calcium absorption in the intestine.
The vitamin D receptor belongs to the nuclear receptor superfamily of steroid/thyroid hormone receptors, and VDRs are expressed by cells in most organs, including the brain, heart, skin, gonads, prostate and breast. VDR activation in the intestine, bone, kidney, and parathyroid gland cells leads to the maintenance of calcium and phosphorus levels in the blood (with the assistance of parathyroid hormone and calcitonin) and to the maintenance of bone content.
One of the most important roles of vitamin D is to maintain skeletal calcium balance by promoting calcium absorption in the intestines, promoting bone resorption by increasing osteoclast number, maintaining calcium and phosphate levels for bone formation, and allowing proper functioning of parathyroid hormone to maintain serum calcium levels.
Vitamin D deficiency can result in lower bone mineral density and an increased risk of reduced bone density (osteoporosis) or bone fracture because a lack of vitamin D alters mineral metabolism in the body. Thus, vitamin D is also critical for bone remodeling through its role as a potent stimulator of bone resorption. The VDR regulates cell proliferation and differentiation. Vitamin D also affects the immune system, and VDRs are expressed in several white blood cells, including monocytes and activated T and B cells.
In vitro, vitamin D increases expression of the tyrosine hydroxylase gene in adrenal medullary cells, and affects the synthesis of neurotrophic factors, nitric oxide synthase, and glutathione. Vitamin D receptor expression decreases with age. A diet with insufficient vitamin D in conjunction with inadequate sun exposure causes vitamin D deficiency, which is defined as a blood 25(OH)D level below 12 ng/mL (30 nmol/liter), whereas vitamin D insufficiency is a blood 25(OH)D level of 12-20 ng/mL (30-50 nmol/liter).
An estimated one billion adults worldwide are either vitamin D insufficient or deficient, including in developed countries in Europe. Severe vitamin D deficiency in children, a rare disease in the developed world, causes a softening and weakening of growing bones, and a condition called rickets. Vitamin D deficiency is found worldwide in the elderly and remains common in children and adults.
Deficiency results in impaired bone mineralization and bone damage which leads to bone-softening diseases,including rickets in children and osteomalacia in adults. Low blood calcifediol (25-hydroxy-vitamin D) can result from avoiding the sun.
Being deficient in Vitamin D can cause the absorption of dietary calcium to fall from the normal fraction (between 60 and 80 percent) to as little as 15 percent. Dark-skinned people living in temperate climates have been shown to have low vitamin D levels. Dark-skinned people are less efficient at making vitamin D because melanin in the skin hinders vitamin D synthesis.
Vitamin D deficiency is common in Hispanic and African-Americans in the United States, with levels dropping significantly in the winter. This is due to the levels of melanin in the skin, as it acts as a natural protectant from sun exposure. Supplementation with vitamin D is a reliable method for preventing or treating rickets. On the other hand, the effects of vitamin D supplementation on non-skeletal health are uncertain.
A review did not find any effect from supplementation on the rates of non-skeletal disease, other than a tentative decrease in mortality in the elderly. Vitamin D supplements do not alter the outcomes for myocardial infarction, stroke or cerebrovascular disease, cancer, bone fractures or knee osteoarthritis.
A US Institute of Medicine (IOM) report states: "Outcomes related to cancer, cardiovascular disease and hypertension, and diabetes and metabolic syndrome, falls and physical performance, immune functioning and autoimmune disorders, infections, neuropsychological functioning, and preeclampsia could not be linked reliably with intake of either calcium or vitamin D, and were often conflicting."
Some researchers claim the IOM was too definitive in its recommendations and made a mathematical mistake when calculating the blood level of vitamin D associated with bone health. Members of the IOM panel maintain that they used a "standard procedure for dietary recommendations" and that the report is solidly based on the data..
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