Vitamin D deficiency is linked to an increased risk of cancer, researchers have told attendees at the annual meeting of the American Association for Cancer Research, with results from a clinical trial hoped to show benefits of high-dose vitamin D replacement in individuals with a high risk of lung cancer.
The link between vitamin D intake and protection from cancer dates from the 1940s when Frank Apperly demonstrated a link between latitude and deaths from cancer, and suggested that sunlight gave "a relative cancer immunity."
Two inactive precursors
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Increased risk of number of cancers
Donald Trump, president and CEO of Roswell Park Cancer Institute told attendees at the American Association for Cancer Research's centennial meeting that substantial epidemiological data indicate a link between low vitamin D levels and an increased risk of a number of cancers.
Trump said that no large-scale prospective trials have been conducted to test the hypothesis that aggressive vitamin D supplementation may influence cancer risk, and Roswell Park Cancer Institute recently initiated a clinical trial of high-dose vitamin D3 in individuals with high risk of lung cancer.
"The goal of this study is to delineate the biologic effects of 1,25(OH)2D supplementation in high-risk patients," said Trump.
Preclinical studies have demonstrated an anti-proliferative and pro-differentiative effects of high-dose 1,25(OH)2D in vitro and in vivo, said Trump, with all tumour models sensitive to vitamin D.
"While preclinical data and limited clinical data strongly suggest that 1,25(OH)2D… has a role in the suppression of established cancer, there are numerous unanswered questions about optimal dose, schedule and formulation of 1,25(OH)2D," said Trump.
More vitamin D necessary
Calls to increase vitamin D intake have been growing. Indeed, only recently fifteen experts from universities, research institutes, and university hospitals around the world called for international agencies to "reassess as a matter of high priority" dietary recommendations for vitamin D because current advice is outdated and puts the public at risk of deficiency (The American Journal of Clinical Nutrition, Vol. 85, pp. 860-868).
A recent review of the science reported that the tolerable upper intake level for oral vitamin D3 should be increased five-fold, from the current tolerable upper intake level (UL) in Europe and the US of 2000 International Units (IU), equivalent to 50 micrograms per day, to 10 000 IU (250 micrograms per day). - (Decision News Media, April 2007)
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