Physical activity and dietary calcium interactions in bone mass in Scottish postmenopausal women.
In this population-based cohort of 1,254 older Scottish women we found significant interactions between the mechanical component of self-reported habitual physical activity (PA) and dietary calcium (Ca) in BMD, independent of other risk factors. At low and/or medium Ca intakes BMD was higher amongst the most active people.


BACKGROUND
Although there is general agreement that increased activity (PA) and dietary calcium (Ca) consumption may help maintain bone mass in later life and prevent fractures, the amount required remains uncertain.


METHODS
In 2001-2003, 1,847 postmenopausal women (mean +/- SD age: 69.3 +/- 5.5 years) underwent bone mineral density (BMD) measurement and, in 2004, 68.7% (n = 1,254) completed a bone-specific Physical Activity Questionnaire (bsPAQ) and a food frequency questionnaire. The bsPAQ measures the metabolic and mechanical components of PA. Interactions of PA and Ca in BMD were examined using ANCOVA.


RESULTS
Significant interactions were identified in the BMD of the lumbar spine (LS), right hip (RH) and left hip (LH), after adjustment for confounders, between tertiles of PA classified according to the mechanical component and tertiles of energy-adjusted Ca intake (ANCOVA p = 0.006, p = 0.004 and p = 0.013 respectively). For example, at medium Ca intakes LH BMD was higher by 7.8% in the highest tertile of PA compared with the lowest tertile of PA.


CONCLUSIONS
These data suggest that health promotion campaigns to increase PA would be most effective in populations with a low/medium calcium intake.
Mavroeidi
A
A
School of Medical Sciences, University of Aberdeen, Aberdeen, UK. a.mavroeidi@abdn.ac.uk
Stewart
A D
AD
Reid
D M
DM
Macdonald
H M
HM
D015502:Absorptiometry, Photon; D000368:Aged; D015519:Bone Density / Q000502:physiology*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D015331:Cohort Studies; D004034:Diet Surveys; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D017698:Postmenopause; D012307:Risk Factors; D012606:Scotland; D011795:Surveys and Questionnaires
D002136:Calcium, Dietary