Subject: High animal protein intake increases risk of bone loss and
fractures in elderly women, UCSF study finds
EMBARGOED FOR RELEASE: 22 DECEMBER 2000 AT 05:00
ET US
Contact: Leslie Harris
[2][log in to unmask]
415-885-7277
[3]University of California, San Francisco
Elderly women who get a much higher intake of their dietary
protein
from animal products rather than vegetables have an increased
risk of
bone loss and hip fracture, a University of California, San
Francisco
study has found, suggesting women may be able to improve
bone health
by eating more vegetables.
"We should be encouraged to eat more vegetables and realize
that our
diets play an important role for our bones as we get older," said
lead author Deborah Sellmeyer, MD, UCSF assistant professor
of
medicine and director of the Bone Density Clinic at UCSF
Medical
Center at Mount Zion. "There are lots of things we can do to
improve
bone health."
The study will be published in the January issue of the American
Journal of Clinical Nutrition.
In the study, researchers gave 1,035 women enrolled in the Study of
Osteoporotic Fractures a food frequency questionnaire, asking how
much they ate of 64 different kinds of foods. They broke the food
down into grams of protein, potassium, salt and other categories.
They scrutinized the protein part more carefully, determining how
much protein the women were getting from animal products compared
with vegetables.
The women, ages 65 to 80, were grouped into three categories: those
with a high ratio of animal to vegetable protein, a middle range
ratio and low ratio, Sellmeyer explained. Researchers took the ratio
and compared it with bone mineral density, bone loss and fractures in
a seven year follow up period.
While there was no difference in initial bone mineral density among
the groups of women, the high ratio category had three times the rate
of bone loss as the women in the low group during the follow up
period. The high group also had 3.7 times the rate of hip fractures
compared to the low group. This is after researchers adjusted for
age, weight, estrogen use, tobacco use, exercise, total calcium
intake and total protein intake.
"We adjusted for all the things that could have had an impact on the
relationship of high animal protein intake to bone loss and hip
fractures," Sellmeyer said. "But we found the relationship was still
there."
The most significant possible reason for this link between high
animal protein and bone loss and hip fractures is because animal
products have a high amount of acid, Sellmeyer said. Too much acid
may be detrimental to bone health. While vegetables have some acid,
they have much higher levels of base. Base is a bicarbonate, a
substance that works to neutralize acid. The body works to achieve a
balance between base and acid and gets rid of excess acid through
urine.
"Our bodies don't like too much acid so our kidneys help us adjust by
excreting the acid in urine," Sellmeyer said. "But as we get older,
our kidneys are less and less capable of excreting the acid."
This causes bone-which is built of base and other components-- to
step in to neutralize the acid. As a byproduct of this action, the
bone dissolves over time-causing it to lose mass and calcium.
"We believe this happens very slowly, over decades," Sellmeyer
said. Decreased bone mass makes fractures more likely.
While it appears that increasing vegetable protein intake and
decreasing animal protein intake can decrease the risk of bone loss
and hip fracture in elderly women, Sellmeyer stressed that the point
of the study is not to recommend women give up eating meat or cheese.
"Protein is very important in maintaining strong bones and muscles.
We don't want people to stop eating animal protein," she said. "But
we do want people to work in more fruits and vegetables into their
diets--not only because of the impact it could have on bone health,
but also the impact it can have on lowering the risk of heart
disease, diabetes and other illnesses. This study is yet another
reason to eat more fruits and vegetables."
###
Other study authors are Katie L. Stone, PhD, specialist in the UCSF
School of Medicine; Anthony Sebastian, MD, UCSF professor of medicine
and co-director of the General Clinical Research Center, and Steven
R. Cummings, MD, UCSF professor of medicine.
The National Institutes of Health funded this study.
______________________________________________________________
|