Vegetarian-style dietary pattern during adolescence has long-term positive impact on bone from adolescence to young adulthood: a longitudinal study.

BACKGROUND
The amount of bone accrued during adolescence is an important determinant of later osteoporosis risk. Little is known about the influence of dietary patterns (DPs) on the bone during adolescence and their potential long-term implications into adulthood. We examined the role of adolescent DPs on adolescent and young adult bone and change in DPs from adolescence to young adulthood.

METHODS
We recruited participants from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-2011). Data from 125 participants (53 females) for adolescent analysis (age 12.7 ± 2 years) and 115 participants (51 females) for adult analysis (age 28.2 ± 3 years) were included. Bone mineral content (BMC) and areal bone mineral density (aBMD) of total body (TB), femoral neck (FN) and lumbar spine (LS) were measured using dual-energy X-ray absorptiometry. Adolescent dietary intake data from multiple 24-h recalls were summarized into 25 food group intakes and were used in the principal component analysis to derive DPs during adolescence. Associations between adolescent DPs and adolescent or adult BMC/BMD were analyzed using multiple linear regression and multivariate analysis of covariance while adjusting for sex, age, the age of peak height velocity, height, weight, physical activity and total energy intake. Generalized estimating equations were used for tracking DPs.

RESULTS
We derived five DPs including "Vegetarian-style", "Western-like", "High-fat, high-protein", "Mixed" and "Snack" DPs. The "Vegetarian-style" DP was a positive independent predictor of adolescent TBBMC, and adult TBBMC, TBaBMD (P < 0.05). Mean adolescent TBaBMD and young adult TBBMC, TBaBMD, FNBMC and FNaBMD were 5%, 8.5%, 6%, 10.6% and 9% higher, respectively, in third quartile of "Vegetarian-style" DP compared to first quartile (P < 0.05). We found a moderate tracking (0.47-0.63, P < 0.001) in DP scores at individual levels from adolescence to adulthood. There were an upward trend in adherence to "Vegetarian-style" DP and an downward trend in adherence to "High-fat, high-protein" DP from adolescence to young adulthood (P < 0.01).

CONCLUSION
A "Vegetarian-style" DP rich in dark green vegetables, eggs, non-refined grains, 100% fruit juice, legumes/nuts/seeds, added fats, fruits and low-fat milk during adolescence is positively associated with bone health.