Amino Acid Profile Associated with Bone Mineral Density and Fracture Risk in Older Adults

by | Apr 27, 2021 | 2019, Aging, Amino Acids, Bone Health

Written by Angeline A. De Leon, Staff Writer. This study suggests that a specific amino acid (AA) profile is associated with greater bone mineral density (BMD) and lower subsequent fracture risk, independent of diet and lifestyle factors.

bone healthWith increasing age, the risk of osteoporotic fracture grows exponentially 1, with decreased bone mineral density (BMD) representing the most significant risk factor for fracture 2. While strategies for maintaining and/or improving bone strength have typically relied on bolstering protein intake, the effects of dietary protein on BMD remain mixed 3,4. An emerging view in the study of bone health suggests that such inconsistencies in the literature may be due to differences in protein sources and amino acid (AA, building block of proteins) composition 5. A growing body of evidence indicates that specific AAs are particularly beneficial for bone health, with branched-chain AAs (BCAAS), for example, playing a role in muscle protein synthesis 6 and aromatic AAs (AAAs) supporting skeletal growth through regulation of insulin-like growth factor-1 (IGF-1) levels 7. Newer work suggests that osteoporosis is associated with specific changes in circulating AA profile 8 and that certain AAs, such as tryptophan and glutamine, are correlated to BMD 9. To further explore the relationship between AA profile and bone health, particularly in later life, a longitudinal study 10 published in Bone (2020) looked at the associations of BCAAs, AAAs, and sulphur-containing AAs (SAAs) with BMD and osteoporotic fracture risk in older adults.

A large-scale longitudinal cohort study was conducted with 2,997 older adults living in China (mean age = 72.5 years) who completed an AA assay at baseline. Measured serum AAs included BCAAs (valine, leucine, isoleucine), AAAs (phenylalanine, tryptophan, tyrosine), and SAAs (methionine, taurine, total homocysteine [tHcy]). Lifestyle data (physical activity levels, smoking and alcohol consumption, etc.) and dietary data (based on food frequency questionnaires) were collected at baseline, and hip BMD was assessed at baseline and at 4-year-follow-up. Incidence of major osteoporotic fractures (MOFs) was tracked over a median follow-up period of 9.6 years.

After multiple adjustments for variables like age, protein intake, physical activity level, and body fat concentration, statistical analyses revealed that among BCAAs, higher serum valine (per 1 standard deviation increase in AA concentration, Odds Ratio = 0.83, 95% Confidence Interval: 0.75 to 0.91), leucine (OR = 0.92, 95% CI: 0.87 to 0.98), and isoleucine (OR = 0.87, 95% CI: 0.79 to 0.96) were associated with lower risk of BMD decline over 4 years. Among AAAs, tryptophan was linked to BMD decline (OR = 0.88, 95% CI: 0.80 to 0.96), and among SAAs, tHcy (OR = 1.16, 95% CI: 1.05 to 1.27). After multiple adjustments, each 1 SD increase in serum tryptophan was found to predict a 14% lower risk of incident MOFs (Hazard Ratio = 0.86, 95% CI: 0.75 to 0.98). Conversely, in men, higher serum tHcy was linked to higher incident risk of MOFs (HR = 1.29, 95% CI: 1.12 to 1.50).

General findings point to an association between AA profile and longitudinal change in BMD and fracture risk among older adults. Specific AAs, namely valine, leucine, isoleucine, tryptophan, and tHcy, served as predictors of BMD decline over a 4-year period, independent of dietary and lifestyle factors. High circulating tryptophan was also linked to lower risk of osteoporotic fractures within the next 10 years. Results confirm that maintaining bone health into old age is related not just to overall protein intake, but also to potential differences in protein sources, with specific AAs playing key roles in preserving BMD and preventing fracture risk. The present study benefited from a large sample size with a long follow-up period and complete data on lifestyle and dietary profiles. Limitations relate to a failure to account for the metabolites of serum BCAAs, AAAs, and SAAs and the inability to establish direct causal relationships, given the nature of the study design.

Source: Su Y, Elshorbagy A, Turner C, et al. Circulating amino acids are associated with bone mineral density decline and ten-year major osteoporotic fracture risk in older community-dwelling adults. Bone. 2019; 129: 115082. DOI: 10.1016/j.bone.2019.115082.

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Posted April 26, 2021.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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