Effect of dietary supplementation with conjugated linoleic acid on markers of calcium and bone metabolism in healthy adult men.
BACKGROUND
Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism in experimental animals and cells in culture, but there are limited human data available.


OBJECTIVE
To investigate the effect of CLA supplementation on biomarkers of calcium and bone metabolism in healthy adult males.


METHODS
The study consisted of a double-blind, placebo-controlled trial in which 60 healthy adult males (aged 39-64 y) were randomly assigned to receive daily either 3.0 g CLA isomer blend (50:50% cis-9,trans-11:trans-10,cis-12 isomers) or a palm/bean oil blend (placebo) for 8 weeks. Urine and blood samples were collected at weeks 0 and 8 and were analysed for biomarkers of calcium and bone metabolism.


RESULTS
Supplementation with CLA or placebo for 8 weeks had no significant effects on markers of bone formation (serum osteocalcin and bone-specific alkaline phosphatase) or bone resorption (serum C-telopeptide-related fraction of type 1 collagen degradation products, urinary N-telopeptide-related fraction of type 1 collagen degradation products, urinary pyridinoline and deoxypyridinoline), or on serum or urinary calcium levels. Baseline levels of these biochemical parameters were similar in both groups of subjects. While the placebo had no effect, CLA supplementation resulted in a three-fold increase (P<0.00001) in cis-9,trans-11 CLA isomer in total plasma lipids.


CONCLUSIONS
Under the conditions tested in this double-blind, placebo-controlled trial in adult men, a CLA supplement of mixed isomers did not affect markers of calcium or bone metabolism. Further investigation of the effects of CLA on calcium and bone metabolism in other gender- and age-groups is warranted.
Doyle
L
L
Department of Food and Nutritional Sciences, University College, Cork, Ireland.
Jewell
C
C
Mullen
A
A
Nugent
A P
AP
Roche
H M
HM
Cashman
K D
KD
D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D016723:Bone Remodeling / Q000502:physiology; D001862:Bone Resorption; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged
D015415:Biomarkers; D044243:Linoleic Acids, Conjugated; D002118:Calcium