A long-awaited report from a panel of independent scientists
recommends
tripling the amount of vitamin D most Americans should take and
small
increases in calcium levels for children to build and maintain
strong
bones, but some specialists warned that the recommendations were
flawed.
The Institute of Medicine panel's findings, being released
Tuesday, carry
considerable weight - government agencies rely on the
recommendations to
set food policy, everything from product labeling to requirements
for
school lunch programs. And a raft of health-related organizations,
such as
the National Osteoporosis Foundation, use the guidelines to set
their
policies for nutrient recommendations for specific groups of
patients.
Some research has suggested that consumption of even higher
amounts of
vitamin D could protect against heart disease and various cancers,
but the
panel said that after scrutinizing nearly a thousand studies, it
could not
find sufficient evidence that more vitamin D would be beneficial
and safe.
It said the best evidence it could find showed that the new
recommended
levels of vitamin D and calcium were the optimum ones for building
strong
bones without risking harmful side effects.
"More is not necessarily better for vitamin D," said panel
member Dr.
JoAnn Manson, a Harvard Medical School professor and chief of
preventative
medicine at Brigham and Women's Hospital.
"We need to consider the lessons of other nutrients, such as
vitamin E and
beta-carotene, as cautionary tales," Manson said, referring to
earlier
popular wisdom that those nutrients held promise as weapons against
illnesses. "Randomized clinical trials did not find benefit and
suggested
harm."
For vitamin D, the panel tripled the daily recommended allowance
from 200
international units to 600 units for people aged 1 to 50. It also
recommended that amount for people up age 70. Previously, the
amount for
that group had been 400 units. Over age 70, it recommended 800
units.
The guideline changes for calcium were less dramatic: The panel
suggested
700 milligrams daily for children 1 to 3 years old, up from 500
now; and
1,000 mg. for 4- to 8-year-olds, up from 800. For most adults, the
daily
intake remains at 1,000 mg. It kept the recommended 1,200 mg. for
women
over 50, but reduced the amount for men that age to 1,000.
The guidelines have not been updated by the institute since
1997, and in
the interim various organizations have issued their own
recommendations,
producing confusing and sometimes conflicting advice for consumers.
The 14-member panel also concluded that most laboratories are
setting the
bar too high when they measure whether patients have adequate
vitamin D in
their bloodstream, a test that then prompts physicians to prescribe
higher
doses.
"We are not making any blanket statements that if your doctor
recommends
high dose supplements that you should stop taking them," Manson
said.
Instead, she said, the panel's aim was to spur consensus among
labs to
create more uniform, lower guidelines.
Other specialists who were invited by the panel to review its
work said its
recommendations for adequate vitamin D levels fell short, and that
older
patients especially would lose out.
Dr. Bess Dawson-Hughes, director of the Bone Metabolism
Laboratory at Tufts
University, said that the panel's recommendations for how much
vitamin D
patients over age 60 should have in their blood stream was too low.
She said her studies and those of other researchers have shown
that older
patients need higher levels of D in their blood stream than the
panel
recommended.
"The older population will have fewer fractures and falls,
across the
board, if they have higher (blood) levels," said Hughes, who was a
member
of the 1997 panel that last updated the recommendations.
Otherwise, she said, she found the recommendations generally on
target.
But Dr. Walter Willett, chair of the nutrition department at
Harvard's
School of Public Health, said the panel's recommendations for
vitamin D
were too low and its recommendations for calcium too high.
He said the panel's conclusion that the "majority of
Americans" are
receiving adequate amounts of vitamin D is "flawed." He said
strong
evidence indicates that most adults need nearly twice the amount of
vitamin
D that the panel recommended - at least 1,000 units a day, not 600.
He said
there is strong evidence that higher levels of vitamin D not only
reduce
the risk of fractures in older adults, they also reduce the risk
for colon
cancer.
Willett also said that other international panels of scientists,
including
the World Health Organization, recommend half the amount of calcium
for
adults, suggesting 500 milligrams daily, not 1,000. He said strong
evidence
suggested that elevated calcium levels increase the risk of fatal
prostate
cancer, and possibly ovarian cancer. He said that calcium is added
to so
many foods, such as orange juice, that Americans may unwittingly be
consuming far too much calcium.
"These guidelines get translated to dietary policy ... how many
glasses of
milk a day consumers should have ... and schools have to conform to
them,
so they have a big downstream impact," Willett said.
The federal departments of Health and Human Services and
Agriculture are
finalizing new daily guidelines, expected out by year's end, on a
broad
array of nutrients.
A spokesman for the Agriculture Department said it is still
studying the
institute's calcium and vitamin D recommendations.
A spokeswoman for the National Osteoporosis Foundation said her
organization had not yet decided whether to change its
recommendations for
vitamin D intake. The foundation has recommended substantially
higher
levels of vitamin D for adults over 50 - as much as 1,000 units -
than was
included in the institute's new guidelines.
c.2010 The Boston Globe