The risk assessment provides companies with a guide for safe upper levels for product formulations, and consumers with vital information on safe dosage levels from products.
"This risk assessment was needed to show that newer evidence supports the conclusion that vitamin D is much safer then previously thought, particularly because of all the emergence research that shows benefit for vitamin D at higher levels than consumers were traditionally taking," lead author John Hathcock told NutraIngredients.com.
Currently, the tolerable upper intake level (UL) in Europe and the US is set at 2000 International Units (IU), equivalent to 50 micrograms per day. However, recent research, particularly from clinical trials, suggests that this should be raised. The CRN scientists state that this could be raised to 10,000 IU (250 micrograms per day).
"New data continue to emerge regarding the health benefits of vitamin D beyond its role in bone," wrote the reviewers in the American Journal of Clinical Nutrition.
"The intakes associated with those benefits suggest a need for levels of supplementation, food fortification, or both that are higher than current levels."
The reviewers, from the CRN, Mount Sinai Hospital in Toronto and Crieghton University in Nebraska, pooled data from 21 clinical trials using doses ranging from 10 to 2500 micrograms.
The risk assessment also included data from animal studies, some of which used "extraordinarily high doses of vitamin D3".
"The lack of adverse effects in clinical trials that used intake up to 1250 micrograms vitamin D per day and the lack of adverse effects at lower doses inspires a high level of confidence in the data from the strongly designed clinical trials that used 250 micrograms vitamin D per day," said the reviewers.
The researchers also note that for practically all the reported cases of vitamin D toxicity have involved doses that were in excess of those studied in the clinical trials.
"Newer clinical trial data are sufficient to show that vitamin D is not toxic at intakes much higher than previously considered unsafe," said the reviewers.
"This demonstrated safety profile of vitamin D should safely permit increased intakes to achieve additional benefits of this vitamin at higher levels than previously recognised."
Vitamin D is made by the body on exposure to sunshine, or can be consumed in small amounts in milk, fish, liver and egg yolk. However because of the low amounts present in the diet, and lack of sunshine in northern climates, with some estimates claiming that as much as 60 per cent of northern populations may be vitamin D deficient.
And since dietary intakes are small, the best method for getting adequate levels of the vitamin appears to be from supplements and/or fortified foods.
Indeed, the reviewers note that normal dietary sources provide about 2.5 micrograms per day, while this can be increased up to 10 micrograms with fortified foods. Dietary supplements would provide higher doses.
"Unfortified foods, fortified foods, and most dietary supplements, combined, do not contribute to a total exposure anywhere near the recommended vitamin D UL of 250 micrograms per day," they said.
"We applied the same method to our risk assessment as the Food and Nutrition Board had used years ago, and our results concluded vitamin D could be safely taken in much higher amounts," Hathcock told this website.
"We hope that the Food and Nutrition Board along with health professionals and regulators will take our assessment and recommendation seriously," he said.
Source: American Journal of Clinical Nutrition January 2007, Volume85, Pages 6-18 "Risk assessment for vitamin D" Authors: J.N. Hathcock, A. Shao, R. Vieth, R. Heaney