Effects of different dietary intake of essential fatty acids on C20:3 omega 6 and C20:4 omega 6 serum levels in human adults

Four diets which differed in fatty acid composition were provided for five months each to a group of 24 healthy nun volunteers. The diets contained 54% carbohydrates, 16% proteins and 30% lipids. One-third of the lipid part remained unchanged during the whole study, and two-thirds were modified during each period. For this latter portion, one of the following dietary fats was used: sunflower oil, peanut oil, low erucic acid rapeseed (LEAR) oil or milk fats. This procedure allowed an evaluation of the effects of various amounts of dietary linoleic acid (C18:2 omega 6) and alpha-linolenic acid (C18:3 omega 3) on the serum level of their metabolites. A diet providing a large amount of linoleic acid (14% of the total caloric intake) resulted in low levels of dihomo-gamma-linolenic acid (C20:3 omega 6) and arachidonic acid (C20:4 omega 6) in serum phospholipids and cholesteryl esters. A diet providing a small amount of linoleic acid (0.6% to 1.3% of the total caloric intake) induced high levels of omega 6 fatty acid derivatives. Intermediate serum levels of C20:3 omega 6 and C20:4 omega 6 were found with a linoleic acid supply of about 6.5% of the total caloric intake. Serum levels of omega 6 metabolites were not different after two diets providing a similar supply of C18:2 omega 6 (4.5% to 6.5% of the total caloric intake), although in one of them the supply of C18:3 omega 3 was higher (1.5% for LEAR oil versus 0.13% for peanut oil).(ABSTRACT TRUNCATED AT 250 WORDS)