Study: 40 percent of U.S. may be deficient in vitamin D
According to the study, a person would have to drink 2 quarts of milk a day to get a sufficient amount of vitamin D
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March 18, 1998
Web posted at: 8:55 p.m. EST (0155 GMT)
BOSTON (CNN) -- Researchers estimate that as much as 40 percent of the U.S. population -- including many who take recommended vitamin dosages -- may lack sufficient quantities of the essential vitamin D.
A study conducted by the Harvard Medical School found that nearly 60 percent of patients at a Boston hospital were deficient in vitamin D, and that 46 percent of those who took vitamin supplements still lacked enough vitamin D.
Based on their findings, they estimate that between 30 and 40 percent of healthy Americans may be vitamin D deficient.
"Vitamin D deficiency is much more common than most people had anticipated," said study co-author Dr. Joel Finkelstein.
Too little vitamin D can lead to weak bones
Vitamin D is needed so bones will absorb calcium. Evidence is accumulating, however, that it may also be essential to muscle function, immune defenses and warding off some kinds of cancer.
When the body fails to get enough, the bones soften, producing rickets, or a condition known as osteomalacia. In older people, too little vitamin D increases the risk of a bone fracture.
The body makes vitamin D naturally from exposure to sunlight, and in tropical climates the sun alone is usually enough to make adequate vitamin D.
However, people in the north typically make little vitamin D in the winter, when the sun is weak and they stay indoors or cover most of their skin when they go outside.
'Dramatic results' surprise researchers
Vitamin D is found in oily fish, tuna, salmon, dairy products and eggs. Most foods naturally contain some vitamin D, although it is added to milk and many brands of cereal. A quart of milk contains 400 international units.
The vitamin can also be given as a shot that lasts for four
to six months.
The study, which appears in Thursday's edition of the New England Journal of Medicine, was conducted on 290 consecutive patients admitted to Massachusetts General Hospital's general medical wards in 1994.
It was conducted in March, when vitamin D levels in the northern states are typically the lowest, and in September, when they are highest.
Overall, 57 percent of the patients were vitamin D deficient, 22 percent severely. Forty-six percent of those who said they took vitamins regularly were nonetheless deficient in vitamin D, and a third of those who said they consumed the recommended amounts from cereal and milk also lacked sufficient vitamin D.
But the study suggests that it's not just the old and sick who lack vitamin D. Researchers studied 77 people who were under age 65 and reasonably healthy and found that 42 percent were vitamin D deficient -- 11 percent severely so.
"Although we expected to see significant levels of vitamin
D deficiency in the patients studied (because they were ill or housebound), we were surprised the results were so dramatic," Finkelstein said.
Degree of deficiency a surprise
Liver is a good source of vitamin D
The researchers said the degree of the deficiency was a surprise, even in Boston where the winter climate aggravates the problem. They said it suggests that too little vitamin D is probably an underappreciated condition across much of the country.
They recommend that people be routinely screened for vitamin D deficiency, and that vitamin D supplements should be more widely used. Stand-alone vitamin D pills are not widely available.
Dr. Melissa K. Thomas, who directed the study, said she recommends that patients who are deficient in vitamin D take two multivitamin pills a day. One multivitamin typically contains 400 international units of vitamin D.
In an accompanying editorial, Dr. Robert D. Utiger, a deputy editor of the journal, said the findings "support the conclusion that many people do not take the recommended amount, however defined, and that this amount is too low anyway."
"Even the new 'adequate intake' values may be too low," Utiger said. "Sick adults, older adults, and perhaps all adults probably need 800 to 1,000" units daily.
Utiger also suggested that more foods be fortified with vitamin D.
Dosage increase disputed
But Dr. Bess Dawson-Hughes, a bone loss researcher at Tufts University, said increased dosages were "a very bad idea, because people could take in too much vitamin A, which can be hazardous.
She and other members of a committee of the Institute of Medicine recently recommended -- and the federal government agreed -- that Americans aged 51 to 70 increase their vitamin D intake from 200 to 400 units, and that those over 70 take 600 units.
Correspondent Elizabeth Cohen and Reuters contributed to this report.