Some of the most sensational health claims ever advanced about a nutrient have recently been made for vitamin D. Not having enough of the sunshine vitamin has been linked to a slew of chronic ailments, including cancer, heart disease and diabetes.
Now, the purported benefits of taking extra vitamin D are about to receive high-level scientific scrutiny through a review conducted at the behest of the Canadian and U.S. governments. But the effort is already mired in controversy.
The panel selected to analyze the health claims is being criticized for not including the medical researchers whose work prompted intense scientific interest in the nutrient in the first place.
"If you were publicly in favour of vitamin D, you were not included, and I find that outrageous," said Reinhold Vieth, a professor in the department of nutritional sciences at the University of Toronto, and one of Canada's leading experts on the nutrient.
The composition of the panel, which had its first meeting last week in Washington and is chaired by an authority on vitamin A, has prompted concerns that it may not settle the contentious question of whether current vitamin D recommendations need to be revised upward.
Health Canada and U.S. health authorities call for taking 200 to 600 international units a day, depending on age. The levels were set mainly for the prevention of childhood rickets, a bone disease.
These levels are the reason typical multivitamins contain only 400 IU and fortified foods, such as milk, contain 100 IU per cup.
Since these intake amounts were set in 1997, there has been a flurry of research questioning their adequacy.
Many of the scientists conducting studies that found benefits from having more vitamin D, including Dr. Vieth, have publicly asserted that the current recommendations are woefully inadequate and that 2,000 IU daily or more may be needed for optimal health.
The Canadian Cancer Society has also recommended taking more - 1,000 IU daily - as a possible cancer-prevention step.
Dr. Vieth proposed six top vitamin D experts for the panel, but they were all rejected. They included Cedric Garland of the University of California, San Diego, one of the scientists who discovered a link between low vitamin D levels and colon cancer incidence, and Joan Lappe, a researcher at Creighton University who co-authored a study in 2007 that found women taking 1,100 IU a day as well as calcium supplements had a 60-per-cent reduction in cancer incidence.
Dr. Vieth says he has "total respect" for those selected to serve on the panel, but adds that as a group they do not represent the full scope of scientific expertise available.
The panel was assembled by the Washington-based Institute of Medicine after it solicited names of possible participants from the two governments and the research community. Health Canada and the U.S. government are paying for the panel, which also did the 1997 review, but the institute is conducting the work on an arms-length basis.
Christine Taylor, the institute's spokesperson for the vitamin D panel, denied that medical researchers who have publicly criticized current recommendations were excluded. "Certainly not," she said. "That would not have been a consideration at all."
She said the 13 experts chosen to sit on the panel were picked because they had expertise in such areas as bone metabolism, cancer and calcium levels, and she pledged that the panel would conduct a thorough review of claims about the vitamin.
Health Canada, in response to e-mailed questions from The Globe and Mail, said it submitted names for the panel but wouldn't identify them.
