Evidence builds for boosting vitamin D levels

by Jeff Gelski
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A meta-analysis soon to be published provides evidence that the daily Adequate Intake (A.I.) level of vitamin D for the elderly may need to increase. Among youth, however, more research may be required before their A.I. level for vitamin D is raised, according to a presentation given Aug. 4 by Connie Weaver, distinguished professor of food and nutrition at Purdue University in West Lafayette, Ind. She spoke at an Institute of Medicine committee meeting in Washington to discuss intake levels for both vitamin D and calcium.

The committee expects to release a report next May. Revising the A.I. levels potentially may alter how food and beverage manufacturers may achieve label claims for calcium and vitamin D. For example, increasing the A.I. level for calcium or vitamin D also may increase the amount in a product needed to achieve a "good source" or "excellent source" claim.

An updated meta-analysis on vitamin D and the prevention of falls and fractures in people age 65 and older will be published soon in the British Medical Journal, said Bess Dawson-Hughes, a senior scientist at Tufts University in Boston who spoke at the Aug. 4 meeting. The meta-analysis studied low-dose trials (200 to 600 International Units (I.U.) per day) and high-dose trials (700 to 1,000 I.U. per day).

Fall risk reduction begins at a mean administered dose of 700 I.U. per day and increases progressively with higher doses, Dr. Dawson-Hughes said. Non-vertebral fracture risk begins to decrease at a mean received dose of 482 I.U. per day and continues to drop with higher doses.

"These results support the use of higher doses, defined as somewhere north of 700 units in this analysis," she said.

The current A.I. levels for vitamin D are 200 I.U. for people age 0-50, 400 I.U. for people age 51-70 and 600 I.U. for people over age 70.

More research may focus on vitamin D and calcium intake among youths age 0-3, said Stephanie Atkinson, professor in the Department of Pediatrics at McMaster University in Hamilton, Ont. She served on an Institute of Medicine committee that established the current A.I. levels 14 years ago.

"They are often the forgotten group," Dr. Atkinson said of youth age 0-3. "I’m not sure how much richer the data has become over those 14 years."

Researchers may consider special needs for multiple births, closely spaced pregnancies, adolescent pregnancies, interaction of calcium/vitamin D status and skin color/latitude, she said. Dr. Atkinson said she hopes the committee recommends upgrading calcium and vitamin requirements from an A.I. to an estimated average requirement (E.A.R.) or a recommended dietary allowance (R.D.A.).

"Hopefully you will find some nutrient specific data that is geared toward children," Dr. Atkinson said.

Ms. Weaver also spoke about vitamin D and calcium levels among adolescents.

"I don’t think you have really good data for setting vitamin D requirements in adolescents," she said. "You need more research there."

Robert Heaney, a professor in the Department of Medicine at Creighton University in Omaha, spoke about how vitamin D and calcium react.

"The message here is in the absence of vitamin D you cannot absorb enough calcium," Dr. Heaney said, and added the question then becomes how much vitamin D is adequate for this purpose.

He said many studies focus on too small amounts of vitamin D, such as 1,000 I.U. per day and below. He said a study at Creighton involved 66 healthy adults who over a 5-month period were given daily doses of vitamin D that ranged from 0 to 10,000 I.U. per day.

Dr. Heaney said input from all vitamin D sources combined, including sunlight, food and supplements, should range from 3,500 to 5,000 I.U. per day.

Michael Holick, professor of medicine, physiology and biophysics at Boston University School of Medicine, spoke about dietary vs. solar sources of vitamin D. He said he recommends A.I. levels of 400 to 1,000 I.U. for babies up to 1-year-old, 1,000 to 2,000 I.U. for children ages 1-12, and 1,500 to 2,000 I.U. for teenagers and above.

Dr. Holick also advocated raising the safe upper limits for vitamin D. The upper limits currently are 1,000 I.U. for babies up to 1-year-old and 2,000 I.U. for everybody over age 1. Dr. Holick said in his opinion the upper limits should be 2,000 I.U. for neonatal, 5,000 I.U. for children ages 1-12, and 10,000 I.U. for teenagers and adults.

This article can also be found in the digital edition of Food Business News, September 1, 2009, starting on Page 24. Click here to search that archive.

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