Tuesday, November 30, 2010

New vitamin D guidelines, a disappointment

Over the past decade, there has been tremendous excitement in the world of nutrition centered around the "sunshine vitamin" for its association with reducing risk of influenza, osteoporosis, autoimmune diseases, heart disease, and even some cancers such as prostate and breast cancer. 

However, this morning, the Institute of Medicine, of the National Academy of Sciences released new guidelines for vitamin D (and calcium) that will come as a disappointment to several researchers who consider the report too conservative to deal with a widespread epidemic.

"Vitamin D is the most common medical condition in the world, believe it or not" said Michael Holick, of Boston University Medical Center, to me in a recent interview. Holick, who routinely prescribes 2000-3000 IU per day to his patients, has studied Vitamin D for more than 40 years. In the 1970s he was the first to isolate the major circulating form of Vitamin D in plasma, 25-hydroxyvitamin D, as well as the active form produced in the kidneys. 

In his recently published book, The Vitamin D Solution, Holick cites evidence that: 
  • Half of all children in the US and Europe are Vitamin D deficient at some time, but almost every single one has vitamin D insufficiency.
  • Over the last 10 years there's been 22 percent reduced levels of vitamin D in the US
  • Last year, a study published in Archives of Internal Medicine, showed 70 percent of whites, 90 percent of Hispanics and 97 percent of blacks in the US have insufficient levels.
  • Even near the equator (where you'd think people were getting plenty of sun –think Saudi Arabia, India, Australia, Brazil, Mexico – between 30 to 80 percent of children and adults are deficient or insufficient.
  • Three out of four people in the US are deficient, most are insufficient. Twenty years ago it was only 1 out of 2.
  • New research has linked several common problems of poor health and accelerated aging to one single thing – vitamin D deficiency or insufficiency
Despite these data, the IOM reported that most people in the U.S. and Canada should be able to obtain sufficient amounts from their diet to meet Dietary Recommended Intakes (DRIs), assuming no other vitamin D was synthesized from the sun in the skin.

The IOM raised the DRIs of vitamin D to 600 International Units (IU) for ages 1-70 and to 800 IU for ages 70 and older. Previously the DRIs were 200 IU for ages 1-50, 400 IU for ages 51-70, and 600 IU for ages 70 and older.

The Tolerable Upper Limit was also raised from 2,000 IU to 4,000 IU for adults, which will allow major manufacturers such as the dairy industry and Coca Cola who make Minute Maid orange juice to consider doubling vitamin D in their products.

The IOM committee chair Catharine Ross, of Penn State, said that after reviewing more than 1,000 published studies and listening to testimonies of scientists there still wasn't enough solid evidence for raising vitamin D DRIs or ULs any higher.

In a press conference this morning, she said, "What we were not able to do is take the currently available clinical data including randomized clinical trials and use that information for Dietary Recommended Intakes. The data are not sufficient at present to conclude that intakes should be higher."

When asked about why the Upper Limit was not raised higher, Ross said, "We needed to take a cautious approach because we're looking to reduce risk to the public. There's evidence of harm at the level of 10,000 IU. So we used 4000 IU per day." She said that there was a gap in evidence in between the two numbers.

Other scientists on the committee chimed in:

"There's considerably more evidence, a tremendous amount for vitamin D," said Patsy Brannon, of Cornell, yet not enough to guide decision making on greater intake. She added, "There is research that points to risk. There's also research that shows no risk. We also lack RCTs. We're still needing more research."

Oncologist Steven Clinton, of Ohio State University, said, "As you look across the literature there are inconsistencies." For example, regarding calcium, it's associated with less colon polyps, but increased risk in prostate cancer. He says that in the future as more data become available, there will be more individualized approaches.

"We are still interested in this molecule that affects thousands of genes in the body. But we cannot make this leap at this point," added biochemist Glenville Jones, of Queens University.

The committee had been asked to set new guidelines for DRIs of calcium and vitamin D as well as Upper Limit intakes.

What about supplements?

Despite headlines from the New York Times and several other news outlets, the IOM committee voiced that they did not intend for this kind of position and clarified that they did not specify where the vitamin D amounts should come from--whether it be from the sun, supplements or diet.

Clinton added that, "especially in Canada, we don't want to close the door on those supplements. There's possibility of using supplements." Although, he said he wondered about whether or not the Canadian Cancer Society would change its recommendation from 1,000 IU to 600-800 IU in light of the IOM's new recommendations.

When asked what to make of the new recommendations when it's clear that skin synthesis upon sun exposure yielded amounts of 20000 IU or higher, Brannon responded: "We set our recommendations based on data for total consumption of vitamin D."

She added that the difference between dietary intakes and the skin synthesis is that the body has a natural ability to rid itself of excess made by the sun, "The sun giveth, the sun taketh away."

Apart from Holick, other scientists have voiced their opinions like those representing the Vitamin D Council: Bruce Hollis of Medical University of South Carolina and Robert Heaney of Creighton University.

They have long recommended taking a supplement by as much as 5,000 IU per day to maintain blood levels between 50-80ng/mL year-round.

As Science News reports, Hollis called the IOM report "a big waste of money," although agreed with the panel's decision to double recommendations for children. In addition, Heaney said, “I don’t think this does anything to create confidence in IOM recommendations."

The entire IOM report is summed up by registered dietitian Debra Riedesel, who posted on Twitter, as @NutritionistaRD, in response to the debate, "Do you trust the scientists who've researched Vit D for years or 14 IOM scientists who only read the research?"