Pathogenesis of Osteoporotic Fracture LOW PEAK BONE MASS LOW PEAK BONE MASS POSTMENOPAUSAL BONE LOSS POSTMENOPAUSAL BONE LOSS AGE-RELATED BONE LOSS AGE-RELATED BONE LOSS LOW BONE MASS LOW BONE MASS Other Risk Factors Other Risk Factors FRACTURE Poor bone quality (architecture) Poor bone quality (architecture) Nonskeletal factors (propensity to fall) Nonskeletal factors (propensity to fall) Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988, New York, pp Pathogenesis of Osteoporotic Fracture LOW PEAK BONE MASS LOW PEAK BONE MASS POSTMENOPAUSAL BONE LOSS POSTMENOPAUSAL BONE LOSS AGE-RELATED BONE LOSS AGE-RELATED BONE LOSS LOW BONE MASS LOW BONE MASS Other Risk Factors Other Risk Factors FRACTURE Poor bone quality (architecture) Poor bone quality (architecture) Nonskeletal factors (propensity to fall) Nonskeletal factors (propensity to fall) Adapted from Melton LI, Riggs BL, eds. Osteoporosis: Etiology, Diagnosis, and Management. Raven Press, 1988, New York, pp

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 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 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/cm 2 ) –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