Fatty acid composition of adipose tissue and serum lipids are valid biological markers of dairy fat intake in men

The fatty acid intake is in part reflected by the fatty acid composition of adipose tissue and serum lipids. We evaluated whether the proportions of myristic (14:0), pentadecanoic (15:0) and heptadecanoic (17:0) fatty acids in the adipose tissue triacylglycerols and serum cholesterol esters and phospholipids reflect long-term dairy fat consumption in free-living men. In 114 healthy men aged 40-76 y, we compared the relative content of 14.0, 15.0 and 17.0 in subcutaneous adipose tissue and in serum lipids with relative intake (g/100 g of total fat) assessed by two l-wk weighed food records made 6 mo apart and assessed by fourteen 24-h dietary recall interviews equally distributed during 1 y. According to food records, the mean +/- SD dairy fat intake was 24.9 +/- 13.1 g/d (29.6 +/- 10.5 g/100 g total fat); intake of 14:0, 15:0 and 17:0 was 4.6, 0.23 and 0.16 g/100 g total fat, and the content in adipose tissue was 3.6, 0.36 and 0.25 g/100 g fatty acids, respectively. Pearson correlation coefficients between intake of dairy fat (based on 24-h recalls) and fatty acid composition of adipose tissue were 0.64 (P < 0.001) for 14.0, 0.74 (P < 0.001) for 15:0 and 0.60 (P < 0.001) for 15:0 + 17.0. Corresponding correlations with serum cholesterol esters were 0.34 (P < 0.001) (14:0), 0.45 (P < 0.001) (15:0) and 0.56 (P < 0.001) (15:0 + 17:0), and with serum phospholipids the values were 0.30 (P < 0.01) (14:0), 0.50 (P < 0.001) (15:0) and 0.50 (P < 0.001) (15:0 plus 17:0). In our study population, the relative content of 15.0 or 14.0 in adipose tissue is a valid biomarker for long-term dairy fat intake in free-living individuals. When adipose tissue is not available, 15:0 content in serum cholesterol esters or phospholipids might be used. Intake data based on repeated 24-h recalls are equally informative and may be an equivalent choice in nutritional studies.