Association of dietary consumption and serum levels of vitamin A and β-carotene with bone mineral density in Chinese adults.

Background: Former studies suggested an adverse effect of hypervitaminosis A on bone health, while the effects of retinol and its precursor (β-carotene) remain uncertain in populations consuming vitamin A (VA) mainly from plant sources.
Objective: We investigated the association of serum, dietary retinol, and β-carotene with bone mineral density (BMD) in Chinese adults.
Methods: We recruited 2101 women and 1053 men (aged 40-75 years) in Guangzhou, China. Dietary intake was assessed through face-to-face interviews with food-frequency questionnaires at baseline and 3 years later. Serum levels of retinol and β-carotene were determined by HPLC using a baseline specimen, and the BMD for the whole body (WB), lumbar spine (LS), total hip (TH), and femur neck (FN) were measured using dual energy X-ray absorptiometry at follow-up.
Results: In general, greater levels of serum retinol, β-carotene, and the β-carotene-to-retinol ratio were associated with a higher BMD after adjustment for potential covariates in the total sample. BMD values in the top (vs. bottom) quartile were increased by 2.06% (TH) for retinol; 2.87% (WB), 2.51% (LS), 3.10% (FN) for β-carotene; 2.21% (WB) and 2.05% (FN) for the β-carotene-to-retinol ratio in the total sample (all p<0.05). A significant positive association with BMD was observed for dietary intake of β-carotene and total VA in retinol equivalents at the hip sites in the total sample.
Conclusion: Higher circulating and dietary levels of VA and β-carotene and higher serum β-carotene-to-retinol ratios were positively associated with BMD in Chinese adults consuming relatively low levels of VA, mainly from plant foods.
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