WASHINGTON — Although it triples the amount of recommended daily vitamin D levels for many age groups, a report issued Nov. 30 by the Institute of Medicine also finds most Americans and Canadians are getting enough vitamin D and calcium. According to the report, calcium and vitamin D promote bone health, but more evidence is needed to support other health benefits, such as protecting against cancer.
“What we have concluded may be surprising to some,” said A. Catherine Ross, chair of the I.O.M. committee and a professor in the Department of Nutritional Sciences at Pennsylvania State University in University Park, Pa.
The I.O.M. set daily reference intakes (D.R.I.s) for vitamin D at 600 international units (I.U.) for people age 1 to 70 and at 800 I.U. for people over age 70. These levels compare to I.O.M. levels set in 1997 of 200 I.U. for people up to age 50, 400 I.U. for people age 51 to 70, and 600 I.U. for people over age 70. People may receive vitamin D through sunshine, food and dietary supplements. The D.R.I.s for vitamin D take into account food and dietary supplements, but the I.O.M. does not specify which source people should consume, Dr. Ross said. She mentioned fatty fish such as salmon as a source of vitamin D along with fortified foods such as milk, breakfast cereal and juice.
Calcium levels did not change nearly as much. According to the new report, the amount of calcium that people need ranges based on age from 700 to 1,300 mg per day. The D.R.I.s serve as a guide for good nutrition and provide the basis for developing nutrient guidelines in both the United States and Canada.
The report’s recommendations take into account nearly 1,000 published studies as well as testimony from scientists and stakeholders. After reviewing national surveys of blood levels, the committee determined the majority of Americans and Canadians are getting enough vitamin D and calcium. The I.O.M. said there has been confusion about the amount of vitamin D needed to prevent deficiency. Measurement labs used to determine if someone is deficient are not standardized with different labs using different standards, leading to potential overestimation of deficiency.
“This widespread problem we couldn’t see to exist,” Dr. Ross said of vitamin D deficiency.
Some adolescent girls may not get enough calcium and a greater chance exists that elderly individuals may fall short of the necessary amounts of calcium and vitamin D, according to the report.
The committee that wrote the report confirmed calcium and vitamin D play an important role in promoting skeletal growth and maintenance and amounts needed to avoid poor bone health, but the committee found conflicting and mixed results that did not offer the evidence needed to confirm that vitamin D has an impact in protecting against cancer, heart disease, autoimmune diseases and diabetes. Other studies and reports have suggested such benefits from vitamin D.
“The data was far less consistent than I had originally thought,” Steven K. Clinton, a member of the I.O.M. committee and a professor in the Division of Medical Oncology at The Ohio State University in Columbus, Ohio, said of research on vitamin D and cancer.
Future research may offer more compelling evidence on vitamin D’s effects on diseases.
“We are still very enthusiastic about this molecule (vitamin D),” said Glenville Jones, a member of the I.O.M. committee and a professor in the Department of Biochemistry at Queen’s University in Ontario.
The report also established upper intake levels, suggesting the highest amount of these nutrients people may consume safely, instead of the amounts people should try to consume. Upper intake levels for vitamin D generally doubled and were set at 4,000 I.U. for people age 9 and older. Consuming more than the recommended 600 I.U. to 800 I.U. of vitamin D was not associated with additional health benefits, Dr. Jones said.
The committee also said getting too much calcium from supplements has been associated with kidney stones, and excessive vitamin D may damage the kidneys and heart. There is also some evidence to suggest other risks associated with long-term high vitamin D intake.