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Too Much or Too Little Vitamin Associated With Low BMD in Elderly

Elderly men and women walk a fine line between an adequate consumption of retinol and the risk, particularly in women, that too much retinol supplementation will have a negative effect on their bone mineral density.

While it is well known that retinol is involved in bone remodeling, and excessive intake has been linked to bone demineralization, the researchers point out that there has been little research into its role in osteoporosis.

The researchers from the School of Public Health at the University of North Carolina, Chapel Hill, North Carolina studied 570 women and 388 men, who were between the ages of 55 to 92 at baseline. They assessed the associations of retinol intake with bone mineral density (BMD) and bone maintenance among the men and women in the cohort, who were ambulatory and who lived in the community. They found in analysis adjusted for standard osteoporosis covariates, an inverse U-shaped association of retinol.

Baseline bone mineral density (BMD) and the BMD four years later were compared and analysed with data from questionnaires on diet and supplementation during the 4 year period.

Researchers found that 50 per cent of the women and 39 percent of the men reported they took retinol supplement, which modified the BMD in the women. Users of supplements saw a negative association of their log retinol and their BMD at the hip, femoral neck, and spine.

At the femoral neck, for every unit increase in log retinol intake, those who used supplements had 0.02 g/cm² lower BMD and 0.23 percent greater annual bone loss. In contrast, those men and women who did not use retinol supplements had 0.02 g/cm² greater BMD and 0.22 percent greater bone retention.

Among supplement users, the researchers found that retinol from dietary and supplement sources had similar associations with BMD. This suggests that the total intake of retinol is more important than its source.

"In both sexes, increasing retinol became negatively associated with skeletal health at intakes not far beyond the recommended daily allowance (RDA), intakes reached predominately by supplement users. This study suggests there is a delicate balance between ensuring that the elderly consume sufficient vitamin A and simultaneously cautioning against excessive retinol supplementation" the researchers conclude.
J Bone Miner Res 2002 Aug;17(8):1349-58. "Retinol intake and bone mineral density in the elderly: the Rancho Bernardo Study."

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