Because of it's higher content of sulfur-bearing amino acids, excess
*animal* protein promotes calcium loss much more than excess plant protein.
When excess animal protein is broken down for energy or storage as fat,
acid-forming sulfates are released which require neutralization with calcium
from body reserves before being excreted in the urine (along with the calcium).
Most studies show that excess plant protein isn't a significant risk factor
in osteoporosis. However, a study of 86,000 nurses found that those eating
over 95 grams a day of animal protein (esp. red meat) had 22% more forearm
fractures than those consuming the least.
There are other dietary and lifestyle factors that probably increase
osteoporosis risk more than excess protein:
1. In a recent trial (see Amer. Journal of Clinical Nutrition, 10/95),
sodium intakes over 2600 mg a day increased calcium lossed by as much as 891
mg a day compared to low intakes.
2. Alcohol in excess is the worst beverage for enhancing calicum losses,
more so than coffee or soft drinks. The association of soft drinks with
osteoporosis may have more to do with the calories consumed displacing those
from calcium sources like yogurt and milk.
4. Lack of weight-bearing exercise can easily negate sound dietary habits.
5. Dieting without exercise is especially risky for older women. A study by
the National Institute of Aging found that women over age 50 who lose more
than 10% of their body weight by dieting had twice the risk of hip fractures
unless they also performed regular weight-bearing exercise.
In China and the Third World, calcium intakes average just 300-400 mg/day,
yet osteoporosis is rare, largely due low animal protein intake (just 10% of
ours), greater physical activity, and fewer women who smoke or drink.
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