Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes.
BACKGROUND
The role of caffeine as a risk factor for bone loss is controversial.


OBJECTIVE
Our goals were 1) to compare in both a cross-sectional study and a 3-y longitudinal study the bone mineral density (BMD) of postmenopausal women consuming high or low amounts of caffeine and 2) to study the interaction between caffeine intake, vitamin D receptor (VDR) polymorphism, and BMD in the longitudinal study.


METHODS
The results are derived from cross-sectional measurements of BMD in 489 elderly women (aged 65-77 y) and from longitudinal measurements made in 96 of these women who were treated with a placebo for 3 y. Changes in BMD were adjusted for confounding factors and were compared between groups with either low (< or =300 mg/d) or high (>300 mg/d) caffeine intakes and between the VDR genotype subgroups of the low- and high-caffeine groups.


RESULTS
Women with high caffeine intakes had significantly higher rates of bone loss at the spine than did those with low intakes (-1.90 +/- 0.97% compared with 1.19 +/- 1.08%; P = 0.038). When the data were analyzed according to VDR genotype and caffeine intake, women with the tt genotype had significantly (P = 0.054) higher rates of bone loss at the spine (-8.14 +/- 2.62%) than did women with the TT genotype (-0.34 +/- 1.42%) when their caffeine intake was >300 mg/d.


CONCLUSIONS
Intakes of caffeine in amounts >300 mg/d ( approximately 514 g, or 18 oz, brewed coffee) accelerate bone loss at the spine in elderly postmenopausal women. Furthermore, women with the tt genetic variant of VDR appear to be at a greater risk for this deleterious effect of caffeine on bone.
Rapuri
P B
PB
Bone Metabolism Unit, Creighton University, School of Medicine, Omaha, NE 68131, USA. thiyyari@creighton.edu
Gallagher
J C
JC
Kinyamu
H K
HK
Ryschon
K L
KL
D015502:Absorptiometry, Photon; D000368:Aged; D015519:Bone Density / Q000187:drug effects* / Q000235:genetics*; D002110:Caffeine / Q000008:administration & dosage / Q000009:adverse effects*; D002118:Calcium / Q000378:metabolism*; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D015930:Diet Records; D005260:Female; D005838:Genotype; D006801:Humans; D008137:Longitudinal Studies; D015663:Osteoporosis, Postmenopausal / Q000139:chemically induced* / Q000235:genetics; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D017698:Postmenopause; D018167:Receptors, Calcitriol / Q000235:genetics*; D013131:Spine; D014807:Vitamin D
D018167:Receptors, Calcitriol; D014807:Vitamin D; D002110:Caffeine; D002118:Calcium