Abstract
ABSTRACTAlthough a higher protein intake, particularly from vegetable sources, has been shown to be associated with higher bone mineral density (BMD) the relative impact of specific amino acids on BMD and risk of osteoporosis remains to be determined. Mechanistic research suggests that a number of specific amino acids, including five nonessential amino acids—alanine, arginine, glutamic acid, glycine, and proline—may play a role in bone health, principally through improved production of insulin and insulin‐like growth factor 1 and the synthesis of collagen and muscle protein. However to date, no previous studies have examined the associations between habitual intake of amino acids and direct measures of BMD and prevalence of osteoporosis or osteopenia, and no studies have examined this relationship in discordant identical twin‐pairs. In these analyses of female monozygotic twin‐pairs discordant for amino acid intake (n = 135), twins with higher intakes of alanine and glycine had significantly higher BMD at the spine than their co‐twins with within‐pair differences in spine‐BMD of 0.012 g/cm2 (SE 0.01; p = 0.039) and 0.014 g/cm2 (SE 0.01; p = 0.026), respectively. Furthermore, in cross‐sectional multivariable analyses of 3160 females aged 18 to 79 years, a higher intake of total protein was significantly associated with higher DXA‐measured BMD at the spine (quartile Q4 to quartile Q1: 0.017 g/cm2, SE 0.01, p = 0.035) and forearm (Q4 to Q1: 0.010 g/cm2, SE 0.003, p = 0.002). Intake of six amino acids (alanine, arginine, glutamic acid, leucine, lysine, and proline) were associated with higher BMD at the spine and forearm with the strongest association observed for leucine (Q4 to Q1: 0.024 g/cm2, SE 0.01, p = 0.007). When intakes were stratified by protein source, vegetable or animal, prevalence of osteoporosis or osteopenia was 13% to 19% lower comparing extreme quartiles of vegetable intake for five amino acids (not glutamic acid or proline). These data provide evidence to suggest that intake of protein and several amino acids, including alanine and glycine, may be beneficial for bone health, independent of genetic background. © 2015 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.
Highlights
There is currently no clear consensus on the role of protein in bone health because protein may have competing effects on bone
Arginine, lysine, alanine, proline, leucine, and glutamine have been shown in vitro to stimulate insulin secretion, which promotes osteoblast growth and differentiation.[15,16] Arginine has been shown to stimulate growth hormone secretion thereby promoting production of insulin-like growth factor 1 (IGF-1),(17) whereas arginine, lysine, and glycine have been associated with an improvement in collagen formation or synthesis.[18,19] Leucine has a direct effect on the initiation of mRNA translation and is thought to be the most efficient of the branched-chain amino acids at increasing muscle protein synthesis, which is critical for the maintenance of adequate bone strength and density.[20]
SE 0.01; p trend 1⁄4 0.06) and proline intake and forearm bone mineral density (BMD) (Q5 to Q1: 0.01; SE 0.003; p trend 0.07). This is the first cross-sectional study to examine associations between dietary intakes of amino acids, which have previously been linked in mechanistic research to bone health, BMD, and prevalence of osteoporosis or osteopenia
Summary
There is currently no clear consensus on the role of protein in bone health because protein may have competing effects on bone. We examined for the first time the relationship between intakes of seven specific amino acids with known mechanistic links to bone health, BMD, and prevalence of osteoporosis or osteopenia in a cohort of 3020 healthy women aged 18 to 79 year. On the basis of previous research, it was hypothesized that participants with higher intakes of amino acids that have been shown in vitro to be associated with bone health (alanine, arginine, glutamic acid, glycine, leucine, lysine, and proline) would be associated with a lower prevalence of osteoporosis and higher BMD
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