Dietary tryptophan and bone health: a cross-sectional, population-based study.

Abstract

Tryptophan metabolites, such as serotonin, influence bone. We sought to determine the relationship between dietary intake of tryptophan and bone health in a population-based study of men and women. Participants (1033 women and 900 men, aged 20-98years) enrolled in the Geelong Osteoporosis Study (GOS) were investigated. Dietary information was collected using a validated questionnaire. Tryptophan levels were calculated (mg/day) in accordance with Food Standards Australia and New Zealand and dichotomised according to the median. Bone mineral density (BMD; g/cm2) was measured at the spine (postero-anterior projection) and total hip using dual-energy X-ray absorptiometry. Stiffness index (SI), broadband ultrasound attenuation (BUA) and speed of sound (SOS) were derived from quantitative heel ultrasound. Linear regression models were used to test associations between dietary tryptophan and bone health, after adjustment for potential confounders. Tryptophan intakes ranged from 112 to 3796mg/day (median 1035) in men and 115-2869mg/day (median 885) in women. In men older than 45years and women, a high tryptophan intake was associated with greater hip BMD compared to participants with a low tryptophan intake (p = 0.002 and p = 0.04, respectively); however, these relationships were attenuated by age (all p > 0.05). Participants with high tryptophan intake had greater BUA and SI compared to participants with low tryptophan intake (men; BUA, p = 0.02 and SI, p = 0.02, and women; BUA, p = 0.03 and SI, p = 0.08), yet also attenuated by age (all p > 0.05). No association was found between tryptophan intake and bone health in this population, which suggests a non-critical role of superfluous tryptophan consumption on the skeleton.