High animal protein intake may increase risk of bone loss and fractures in elderly women, UCSF study finds

December 21, 2000

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."
-end-
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.

University of California - San Francisco

Related Protein Articles from Brightsurf:

The protein dress of a neuron
New method marks proteins and reveals the receptors in which neurons are dressed

Memory protein
When UC Santa Barbara materials scientist Omar Saleh and graduate student Ian Morgan sought to understand the mechanical behaviors of disordered proteins in the lab, they expected that after being stretched, one particular model protein would snap back instantaneously, like a rubber band.

Diets high in protein, particularly plant protein, linked to lower risk of death
Diets high in protein, particularly plant protein, are associated with a lower risk of death from any cause, finds an analysis of the latest evidence published by The BMJ today.

A new understanding of protein movement
A team of UD engineers has uncovered the role of surface diffusion in protein transport, which could aid biopharmaceutical processing.

A new biotinylation enzyme for analyzing protein-protein interactions
Proteins play roles by interacting with various other proteins. Therefore, interaction analysis is an indispensable technique for studying the function of proteins.

Substituting the next-best protein
Children born with Duchenne muscular dystrophy have a mutation in the X-chromosome gene that would normally code for dystrophin, a protein that provides structural integrity to skeletal muscles.

A direct protein-to-protein binding couples cell survival to cell proliferation
The regulators of apoptosis watch over cell replication and the decision to enter the cell cycle.

A protein that controls inflammation
A study by the research team of Prof. Geert van Loo (VIB-UGent Center for Inflammation Research) has unraveled a critical molecular mechanism behind autoimmune and inflammatory diseases such as rheumatoid arthritis, Crohn's disease, and psoriasis.

Resurrecting ancient protein partners reveals origin of protein regulation
After reconstructing the ancient forms of two cellular proteins, scientists discovered the earliest known instance of a complex form of protein regulation.

Sensing protein wellbeing
The folding state of the proteins in live cells often reflect the cell's general health.

Read More: Protein News and Protein Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.