A low omega 6 polyunsaturated fatty acid (n 6 PUFA) diet increases omega 3 (n 3) long chain PUFA status in plasma phospholipids in humans.

Background  The competition between omega 6 and omega 3 polyunsaturated fatty acids (n 3 and n 6 PUFA) for both metabolism and incorporation has led to suggestions that reducing dietary n 6 PUFA intake would improve n 3 PUFA status without the need to increase current intake. Aim  To determine the effect of reducing the linoleic acid (LA) content of the diet from ~5 percent to <2.5 percent energy ( percent E) for 4 weeks on n 3 long chain polyunsaturated fatty acid (LCPUFA) status in healthy human subjects. Methods  Thirty six participants (n of 12 males, 24 females) followed a diet with a target LA intake of <2.5 percent E (low LA diet) for 4 weeks. Nutrient intakes were estimated from diet diaries maintained for 2 weeks before and throughout the low LA intervention and blood samples were collected before and after the low LA diet phase for assessment of fatty acid composition in plasma and erythrocyte phospholipids. Results  LA intakes were reduced from 4.6 percent E at baseline to 2.0 percent E during the intervention phase with no change in the intake of n 3 LCPUFA. The LA content of both plasma and erythrocyte phospholipids were significantly reduced at the end of the low LA diet phase, but AA levels in both fractions were unchanged.  The n 3 LCPUFA content was increased in plasma phospholipids at the end of the low LA diet phase compared to baseline (6.22 percent vs 5.53 percent).  Conclusion  These data demonstrate that reducing dietary LA intake for a 4 week period can increase the n 3 LCPUFA status in healthy humans in the absence of any increase in dietary n 3 LCPUFA intake above normal Australian levels. Further studies to assess the longer term effects of low n 6 PUFA diets on clinical outcomes are warranted. (Authors abstract)