Conjugated linoleic acid (CLA) is a natural component of meat and dairy pro
ducts with anticarcinogenic, fat lowering, antiatherogenic and anticataboli
c activity in animals. The purpose of this study was to examine the effect
of CLA supplementation to humans on body fat, certain biochemical parameter
s of serum, and the CLA content of serum lipids. Twenty-two volunteers were
divided into a study group and a control group in a doubly blind design. T
he study group received 0.7 g of CLA for four weeks and 1.4 g of CLA for th
e next four weeks, while the control group received placebo. Diet was contr
olled and no significant differences in energy or macronutrient intake were
found between the two groups. Measurements were taken at baseline, four we
eks, and eight weeks. The sum of the thickness of ten skinfolds, percentage
body fat calculated from it and fat mass was significantly reduced in the
CLA group during the second period (P <0.004) but not overall during the st
udy. Serum HDL-cholesterol decreased significantly (P <0.001) and triacylgl
ycerols as well as total cholesterol tended to decrease in the CLA group du
ring the first period. The CLA content of serum non-esterified fatty acids,
triacylglycerols, phospholipids, and cholesteryl esters increased graduall
y with supplementation; the CLA content of total serum lipids doubled at th
e end of the study compared to baseline. Phospholipids had the highest CLA
content regardless of supplementation. These data indicate that supplementa
tion with 0.7-1.4 g CLA daily for 4-8 weeks may modulate body fat and serum
lipids, as well as increase the CLA content of serum lipids in humans. (C)
2001 Elsevier Science Inc. All rights reserved.