Nutrition, lifestyle, and genetics may all contribute to the decrease in bone mineral density (BMD) that comes with aging and leads to osteoporosis, a major cause of fractures in the elderly. Previous research implicated caffeine in increased risk for hip fracture and poor calcium retention. As part of a larger long-term study of osteoporosis, Rapuri et al. compared the BMD of women in high and low categories of caffeine consumption to examine the interaction between caffeine intake, genetic type, and osteoporosis. They found that women with high caffeine intakes had significantly higher rates of bone loss at the spine, and that women who were homozygous for a mutation in the vitamin D receptor (VDR) gene were at greater risk for caffeine-related bone loss.
The 96 women, averaging 71 years old were not taking any calcium or Vitamin D supplements. Using 7-day food diaries the researchers divided them into low (less than 300 mg/day) or high (greater than 300 mg/day) caffeine intake levels. BMD at the spine, hip, and three other sites was measured, and each subject's VDR genotype was determined. Calculation of the percent change in BMD during the 3-year longitudinal study showed that a caffeine intake of more than 300 mg/day was associated with a higher rate of bone loss at most of the skeletal sites in the spine, although the difference was only significant in subjects carrying the homozygous tt genotype of VDR. Women in the high caffeine category with the tt genotype lost bone density over 3years, compared with no change in bone density the tt women in the low caffeine group.
Though the number of women with the tt genotype was relatively small (6 in the low caffeine group and 5 in the high caffeine group), these findings identify caffeine as a dietary factor, which can alter one's genetic predisposition toward osteoporosis. An editorial by Massey stresses that moderate caffeine ingestion-less than 16 ounces of brewed coffee per day or 32 ounces of brewed tea-is not associated with increased bone loss. Until it is practical to determine each person’s VDR genotype, physicians should recommend both adequate dietary calcium and moderate caffeine consumption for their elderly patients.
Rapuri, Prema B, et al. Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes. Am J Clin Nutr 2001;74:694-700.
Massey, Linda K. Is caffeine a risk factor for bone loss in the elderly? Am J Clin Nutr 2001;74:569-70.
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