September 11, 2015
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Protein, certain amino acids may improve bone health in women

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Women who consume more protein-rich foods — particularly foods containing the amino acids alanine and glycine — are more likely to have a higher bone mineral density and to lower their risk for osteoporosis vs. women who consume less protein, according to research in the Journal of Bone and Mineral Research.

In a cross-sectional study of female identical twins in the United Kingdom, researchers also found that women who consumed a higher proportion of amino acids from vegetable sources, rather than animal sources, lowered their risk for developing osteoporosis or osteopenia.

“The twin population provided the unique opportunity to control for potentially confounding genetic influences by comparing identical twins who were discordant for protein or amino acid intake,” the researchers wrote. “The monozygotic twins with higher intakes of alanine and glycine had significantly higher BMD at the spine than their co-twins.”

Amy Jennings, PhD, of the department of nutrition at Norwich Medical School at the University of East Anglia, and colleagues analyzed data from 3,160 female monozygotic twins (mean age, 48 years) from the TwinsUK registry, a nationwide registry of adult twin volunteers.

Participants completed lifestyle and food frequency questionnaires, allowing researchers to measure amino acid intake and physical activity. Each entry in the food frequency questionnaire had values assigned for 18 individual amino acids; all foods were classified as animal origin, vegetable origin or both. Researchers used DXA to measure BMD at the lumbar spine, femoral neck and peripheral BMD at the forearm.

Aedin Cassidy

Aedin Cassidy

Among the cohort, the average daily total protein intake was 80.5 g, with 16.5% contributing to total energy intake. The most consumed amino acids were glutamic acid (19.8%) and leucine (7.9%).

Among identical twin pairs with differing amino acid intakes (n = 135), researchers found that the women with a higher intake of alanine and glycine had significantly higher BMD at the spine vs. their co-twins (0.012 g/cm² vs. 0.014 g/cm²). Within the cohort, high protein intake was significantly associated with BMD at the spine and forearm, with six specific amino acids — alanine, arginine, glutamic acid, leucine, lysine and proline — associated with higher BMD.

Whether the protein source was vegetable or animal had no effect on BMD at any site, according to researchers; however, the prevalence of osteoporosis or osteopenia was 13% lower in the highest quartile of vegetable protein intake when compared with the lowest quartile.

“Women who eat higher intakes of protein and who eat high levels of certain amino acids (the building blocks of proteins) found in fish/meat and plant-based protein sources have better bone health,” study researcher Aedin Cassidy, PhD, a professor at the University of East Anglia, told Endocrine Today. “Consuming a higher proportion of amino acids from vegetable rather than animal sources showed the greatest benefit. The magnitude of the associations was similar to those previously observed for calcium and vitamin C intake. We need carefully controlled clinical trials to pin down which amino acids and what dose are required for optimal bone health.” – by Regina Schaffer

Disclosure: The researchers report no relevant financial disclosures.