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Tuesday, 26 December, 2000, 00:00 GMT
Meat 'bad for bone health'
Vegetable proteins could be good for bones
Vegetable proteins could be good for bones
Elderly women who get too much protein from animal products like meat and cheese risk fractures and bone loss, researchers are warning.

They say women can improve their bone health by using vegetables as a greater source of protein.

In a study, women who got a high ratio of their protein from meat or dairy products rather than vegetables, had three times the rate of bone loss than those at opposite end of the scale.

But experts insist women should not stop eating meat or cheese and say they should eat more fruit and vegetables instead.

Others say a high protein intake balanced by high calcium will not affect bone health.

Questionnaire

Researchers from the University of California in San Francisco (UCSF) gave more than 1,000 aged 65 to 80 a questionnaire which covered 64 different kinds of foods.

They then broke the results down to show how much of each food group the women ate and looked at how much protein the women got from animal products and how much from vegetables.

They were then categorised into those who ate a high level of animal protein, a medium level and a low level.

Initial bone mineral density checks showing no real differences between the groups were followed up seven years later.

Vegetables - key part of diet
Vegetables - key part of diet
In addition to having three times the amount of bone loss, women who had a high ratio of animal to vegetable protein had 3.7 the rate of hip fractures compared to the low ratio group.

Professor Deborah Sellmeyer, director of the UCSF Bone Density Clinic, said: "We adjusted for all the things that could have an impact on the relationship of high animal protein intake to bone loss and hip fractures, but the relationship was still there."

The cause of the problem could be the high amount of acid in animal products, which Professor Sellmeyer said could be detrimental to bone health.

Loss of mass

Vegetables have some acid, but they have a substance called base - a bicarbonate - which neutralises acid.

She said: "Our bodies don't like too much acid so our kidneys help us adjust be excreting acid in urine.

"But as we get older, our kidneys are less and less capable of excreting the acid."

She said this meant that bones, which are partly made up of base, step in to try to neutralise the acid.


if a high protein diet is matched by a high calcium intake it need not adversely affect bone health

National Osteoporosis Society
Over decades, this process causes the bone to dissolve, causing it to lose mass and calcium. Losing mass increases the risk of fractures.

Professor Sellmeyer added: "Protein is very important in maintaining strong bones and muscles. We don't want people to stop eating animal protein.

"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."

Risk of falling

The National Osteoporosis Society said the issue of whether too much protein affects the body's ability to absorb calcium is currently being debated.

A spokesman said too much protein could have a negative effect on bone health, but added recovery from hip fractures could be helped by protein-rich dietary supplements.

He added: "Malnutrition, and hence a deficiency of protein, has also been shown to contribute to bone loss, the risk of falling, and the response to injury.

"Other studies show that the body can compensate for this extra loss of urinary calcium by absorbing more calcium. So if a high protein diet is matched by a high calcium intake it need not adversely affect bone health."

He added that healthy bones needed a balanced diet.

The study is published in the American Journal of Clinical Nutrition.

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See also:

19 Sep 00 | Health
Lead threat from calcium tablets
24 Aug 99 | Medical notes
Osteoporosis
21 Sep 98 | Health
A baffling bone problem
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