Pathogenesis of Osteoporotic Fracture
LOW PEAK
BONE MASS
Nonskeletal factors
(propensity to fall)
POSTMENOPAUSAL
BONE LOSS
AGE-RELATED
BONE LOSS
LOW BONE
MASS
Other
Risk Factors
FRACTURE
Poor bone quality
(architecture)
Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press
New York, pp 155-179
Objective
• To investigate the influence of dietary
intake on bone mineral density in women
aged 30-39
Design: cross sectional study
• Volunteers (n=139) aged 30-39
• Recruitment from: mailing, newspaper,
health fairs, fliers, referrals
• Exclusions: diseases or medications known
to affect BMD; pregnancy; non-white race
Nutrient Intake
• Current- for year preceding BMD measurement
• Teenage- for ages 13-17
• Nutrients of interest were assessed by modified
Block (NCI) FFQ (self administered):
–
–
–
–
–
–
–
Calcium
Phosphorus
Protein
Vitamin C
Caffeine
Alcohol
Fiber
Food Frequency Questionairre
• Self administered- 94 questions; 30 minutes
• Original for NCI therefore questions
concerned fat, vitamin A etc; (n=35) of
these were deleted.
• Other foods high in calcium were added
(n=23)
• Beverage list was expanded to determine
caffeine in mg/day (n=15)
Covariates:
• Physical measurements:
–
–
–
–
–
–
Height
Weight
Skinfold thickness
Waist circumference
Bioelectric impedence
Grip strength
Covariates:
• Interview:
–
–
–
–
–
–
–
–
Demographics
Menstrual function
Pregnancy and lactation
Oral contraceptive use
Disease and medication history
Fracture history
Smoking
Physical activity
Outcome:
• Bone mineral density by dual x-ray
absorptiometry (gm/cm2)
– Lumbar Spine (L2-L4)
– Hip – femoral neck- trochanter- wards traingle
– Forearm- proximal and distal
Multivariate regression analysis
• BMD= nutrient+ age + height +
weight+ grip strength
Results
• Bone mineral density was not related to
current intake of:
–
–
–
–
–
Caffeine
Vitamin D
Protein
Fiber
Phosphorus
Strengths and Limitations
• Dietary interview detailed and planned for 2 time
periods
• BMD is a reliable measure
• Able to control for many confounders
• Power 77% to detect r=0.20
• Measurement error
• Multicollinearity
• Generalizability
• Multiple comparisons
Conclusion
• A change in calcium intake from 800 to
1200 mg per day will increase hip BMD by
approximately 6%
–
–
–
–
–
Fiber
Supplemental calcium
Phosphorus (r=0.95 with calcium)
Protein (r=0.84 with calcium)
Alcohol
Calcium and BMD
• Strength: moderate r~0.2
– Probably stronger due to RME of dietary
calcium
– Teenage intake
• Specificity
– problem in diet due to high nutrient correlations
– stronger effect with supplements added
– stronger effect after correct for fiber
Calcium and BMD
• Temporality
– Problem with design
– BMD now diet in past year or teenage
• Biological Plausability
– 30% of bone is calcium
– Bone calcium maintains serum calcium
– Greater amount of calcium in cortical bone where
stronger effect is observed
• Consistency