WASHINGTON — Daily doses of 600 international units of vitamin D and between 700 and 1,300 mg of calcium are enough for most children and adults in the United States and Canada, according to a report on new dietary reference intakes issued by the Institute of Medicine.
These new dietary reference intakes for calcium and vitamin D should provide “greater assurance that widespread vitamin D deficiency is not a public health problem,” Dr. Steven Clinton, a member of the IOM committee that issued the report at a press briefing.
After reviewing national databases on blood levels from the United States and Canada, the committee determined that most people in both countries are currently meeting their needs for vitamin D. Adequate vitamin D was defined as blood levels of at least 20 ng/mL as measured in the United States (50 nmol/L as measured in Canada).
Dr. Clinton, a medical oncologist at Ohio State University, Columbus, predicted that physicians will become more comfortable using recommended dietary allowances to advise patients about calcium and vitamin D intake and noted that vitamin D screening “probably should not be part of routine medical care.”
The IOM reviewers examined approximately 1,000 published studies and scientific testimonies to determine the levels of calcium and vitamin D needed to maintain health.
Based on their findings, 700 mg/day of calcium is enough for most children aged 1-3 years, and 1,000 mg is appropriate for most children aged 4-8 years. Older children and teens aged 9-18 years need no more than 1,300 mg/day, and most adults aged 19-50 years and men through 71 years need no more than 1,000 mg daily. For women aged 51 years and older and men aged 71 years and older, 1,200 mg of calcium per day is recommended, but more than that is unnecessary, according to the report.
As for vitamin D, the IOM report states that 600 IU/day meets the needs of almost all children and adults aged 1 year through 70 years, including pregnant and lactating women. For men and women aged 71 years and older, the RDA increases to 800 IU/day to accommodate age-related physical and behavioral changes.
The report lists an upper level for daily vitamin D intake of 1,000 IU for infants up to 6 months of age and 1,500 IU for infants aged 6 months to 12 months. The upper levels for children aged 1-3 years and 4-8 years are 2,500 IU and 3,000 IU, respectively. For all other life stages, the upper level is 4,000 IU.
“What we have concluded may be surprising to some,” Dr. Ross said. “I was surprised to find that vitamin D requirements don't vary much by age.”
The new recommendation came not a moment too soon, said Dr. Russell Chesney, professor and chairman of pediatrics at the University of Tennessee Health Science Center in Memphis, at the annual meeting of the American Academy of Pediatrics in San Francisco.
Dr. Chesney, who cited a long list of potential health benefits for the substance. “Vitamin D truly is the center of the universe,” he joked.
Among the conditions that vitamin D may ameliorate include infectious diseases, ovarian cancer, multiple sclerosis, rheumatoid arthritis, inflammatory bowel syndrome, wheezing, diabetes type 1 and 2, hypertension, atherosclerosis, colorectal cancer, prostate cancer, and breast cancer.
Actually, vitamin D supplementation dates back to the days when mothers spooned cod-liver oil into their children's mouths to prevent rickets. Since then, evidence has mounted for other benefits. Most claims are based on epidemiologic studies. For example, people who live at higher altitudes and get more sunshine exposure – which causes vitamin D synthesis – may suffer less from tuberculosis. “Our ancestors were right when they said we should go to sanatoriums in the mountains,” said Dr. Chesney.
He added that prospective trials are still needed. “This is suspected. This is not proven.”But a few small studies have already reinforced such findings.
In one recent study that Dr. Chesney described, a group of 167 Japanese children took supplements of 1,200 IU of vitamin D, while another group of 167 took a placebo. Those who took the vitamin D had half the influenza incidence of the placebo group, as well as fewer attacks of asthma. Other research suggests that vitamin D inhibits proinflammatory and autoimmune cytokines and promotes those that are anti-inflammatory, said Dr. Chesney.
So many claims of benefits for one vitamin might sound exaggerated, he acknowledged. But it's also true that vitamin D levels are declining in the United States as Americans spend more time indoors and take precautions to avoid skin cancer.