This study evaluating the relationship between protein intake and bone mass in elderly women, included 1077 women around the age of seventy-five. Protein intake was evaluated by food intake questionnaires and bone mass was measured by heel ultrasound at the start and hip bone mineral density after one year.
One third of the women with the lowest protein intake ate less than 66 g. of protein per day and had the lowest bone masses and bone densities. One third of the women with the highest protein intakes ate over 87 g. of protein per day and had the highest bone masses and bone densities. (The daily suggested intake of protein in Australia and the U.S. are 0.75 and 0.80 mg. protein/kg. body weight.)
The results seem to be at odds with previous studies, which have shown a negative effect of protein intake on calcium metabolism. Although calcium intake did increase with protein intake, calcium intake did not significantly correlate with heel bone mass or hip bone mineral density. (High calcium intake seen with high protein intake is probably due to dairy product use.)
High protein diets in young women can cause hypercalciuria (high urine calcium) from increased absorption of calcium in the intestine. Low protein diets have been shown to cause secondary hyperparathyroidism due to reduced absorption of calcium.
CONCLUSION: Women in the group in the highest protein intake had the highest starting bone mass and bone mineral densities at one year. Women eating protein in the lowest third of the group had the lowest bone masses and bone mineral densities. Suggested protein intakes for elderly women may need to be increased for better bone health. “Protein intake over 66 g. protein/d (0.84 g. protein/kg. body wt.) is required in elderly women to maximize bone mass”.
NOTE: A 65 kg. woman eating 0.80 g./kg. of protein per day would be eating only 52 g. of protein and would need to continue eating to reach the U.S. current protein recommendations.
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