MONDAY, March 25, 2002 (HealthDayNews) -- Into the continuing debate over a high-protein diet's link to bone health comes a new study showing that, when coupled with adequate calcium and vitamin D, protein may actually be good for your bones.
For years, scientists have theorized that a high-protein diet could increase the risk of calcium loss.
But in research reported today in the American Journal of Clinical Nutrition, doctors say elderly people who ate a diet high in animal or vegetable protein and took calcium and vitamin D supplements significantly increased their bone density. They did better than either those on a low-protein diet who took the same supplements or those who took no supplements at all.
"We assessed the protein intake of all the participants, and divided them into three groups -- low, middle and high. And our findings were that the higher the protein intake, the better the bone density changes over a period of three years if you were in the calcium-supplemented group," says study author Dr. Beth Dawson-Hughes, a Tufts University scientist.
However, in the control group, the higher amounts of protein had no such positive effect. In fact, Dawson-Hughes says, the more protein consumed without benefit of calcium supplementation, the greater the trend toward bone density loss, although that loss was not considered significant.
She emphasizes that her research does not conclude that a high-protein diet without calcium increases the risk of bone loss. Rather, she says, it suggests the "possibility that consuming more protein can be helpful to bone, as long as you're meeting the calcium requirements."
For endocrinologist Dr. Loren Wissner Greene, the finding is intriguing, partly because past research has shown that high-protein diets can harm bone health, mostly by increasing the rate of urinary calcium excretion and interfering with calcium absorption in the intestines.
"But this study proposes the idea that even if protein does have a negative effect on the bones, you can not only overcome this by the addition of adequate calcium and vitamin D, but that working synergistically, these nutrients may even cause the protein to turn around and become a helpful component," she says.
The latest research, a randomized, placebo-controlled trial, involved 342 healthy men and women over the age of 65. Each was given either a supplement containing 500 milligrams of calcium and adequate vitamin D for absorption or a placebo, which they took daily for three years.
At the start of the study, and in six- months intervals throughout, researchers measured the bone density of the participants, using a system known as dual-energy X-ray absorptiometry. Measurements were taken at various points in the body, including the neck and the spine.
Midway through the study, researchers also gave out a questionnaire to determine intake of both calcium-rich and high-protein foods.
Only at the conclusion of the study did the researchers find out who was taking the calcium supplements and who was not. They then tallied the food questionnaires to determine the amount of protein each person was consuming, as well as their level of dietary calcium.
From that they developed the following subgroups: low, medium and high protein intake, with an average of 870 milligrams of dietary calcium daily; and low, medium and high protein intake with an average of 1,300 milligrams of calcium daily with adequate vitamin D.
After adjusting for influences of age, sex, weight and total calorie intake, they determined that all those on the high-protein diet who took the calcium and vitamin D supplements saw positive effects on bone health. Those who ate the most protein saw the most dramatic effects, particularly in bone-density measurements of the neck.
By comparison, those who had no vitamin/mineral supplementation showed almost no positive changes in bone mass density, no matter how much their protein intake increased.
In fact, says Dawson-Hughes, there was some evidence to show that when higher amounts of protein were consumed without the benefits of calcium and vitamin D, bone health suffered.
What's important to note, she adds, is that even in the group consuming the greatest amount of protein, the level was not unusually high, averaging about 96 grams a day. The recommended amount of daily protein is between 40 grams and 60 grams daily.
For Wissner Greene, the message is that you can't go wrong if you supplement your diet with calcium and vitamin D.
"No matter how much protein you eat, getting adequate calcium and vitamin D will be healthy for your bones," she says.
What To Do
To learn more about bone health, visit The British Nutrition Foundation.
For a fun test of your "Calcium IQ," visit The Association of Reproductive Health Professionals.
