Variations in plasma fatty acid concentrations during a one-year self-selected dietary intake study

A group of healthy volunteers, maintaining their usual lifestyle, was monitored as to their nutrient intake for a period of 1 yr. Diet records were kept daily and blood samples were collected at even intervals five times during the year. Plasma fatty acid levels were analyzed to determine any sex, age, or seasonal variations or if the plasma fatty acid levels could be correlated to dietary fat intake. In the population studied, there was a significant (p less than 0.0001) sex by age interaction, but no seasonal effect was observed. No major differences in plasma fatty acids related to diet were found. However, the younger men had the highest linoleic acid intake and the lowest plasma linoleic acid. Plasma linoleic acid levels for males older than 35 yr of age (87.0 +/- 3.1 mg/dl) were significantly greater than for males younger than 36 yr of age (67.9 +/- 1.8 mg/dl). The plasma linoleic acid levels of all the women were intermediate in value to the men but not different from each other (73.8 +/- 1.7 mg/dl for the younger women and 78.7 +/- 1.9 mg/dl for the older women). There was a significant (p less than 0.01) sex effect in the relative percentage of plasma linoleic acid (34.4 +/- 0.4% for the women and 32.4 +/- 0.6% for the men), but no age or seasonal effect was observed.