Studies suggested that in human adults, linoleic acid (LA) inhibits the biosynthesis of n-3 long-chain polyunsaturated fatty acids (LC-PUFA), but their effects in growing subjects are largely unknown. We used growing pigs as a model to investigate whether high LA intake affects the conversion of n-3 LC-PUFA by determining fatty acid composition and mRNA levels of D5-and D6 desaturase and elongase 2 and -5 in liver and brain. In a 2 3 2 factorial arrangement, 32 gilts from eight litters were assigned to one of the four dietary treatments, varying in LA and a-linolenic acid (ALA) intakes. Low ALA and LA intakes were 0.15 and 1.31, and high ALA and LA intakes were 1.48 and 2.65 g/kg BW 0.75 per day, respectively. LA intake increased arachidonic acid (ARA) in liver. ALA intake increased eicosapentaenoic acid (EPA) concentrations, but decreased docosahexaenoic acid (DHA) (all P , 0.01) in liver. Competition between the n-3 and n-6 LC-PUFA biosynthetic pathways was evidenced by reductions of ARA (.40%) at high ALA intakes. Concentration of EPA (.35%) and DHA (.20%) was decreased by high LA intake (all P , 0.001). Liver mRNA levels of D5-and D6 desaturase were increased by LA, and that of elongase 2 by both ALA and LA intakes. In contrast, brain DHA was virtually unaffected by dietary LA and ALA. Generally, dietary LA inhibited the biosynthesis of n-3 LC-PUFA in liver. ALA strongly affects the conversion of both hepatic n-3 and n-6 LC-PUFA. DHA levels in brain were irresponsive to these diets. Apart from D6 desaturase, elongase 2 may be a rate-limiting enzyme in the formation of DHA.

A cross-over study was done with 19 male and 23 female volunteers living in a monastery and a convent, respectively. The effect of a fat gish (mackerel) diet on the blood serum lipid composition was studied. As the normal diet of these volunteers was of the lacto-ovo-vegetarian type, a control diet in which the fish was replaced by full-fat cheese was used. Subjects consuming the fish diet had a daily uptake of polyunsaturated acids of the omega3 family of about 8 g; comparable amounts of linoleic acid were ingested with both diets. Both diets were consumed for a period of 3 weeks. Serum cholesterol was slightly but significantly (7.5%) lower and serum triglycerides considerably lower (35%) on the fish diet, whereas high density lipoprotein cholesterol increased slightly. Lipoprotein analysis showed a strong very low density lipoprotein decrease by the fish diet while, in the men, both low and high density lipoproteins increased. The fatty acid composition of serum lipids showed considerable differences; C20:5omega3 increased in all fractions and C22:6omega3 was found in the triglycerides and the phospholipids, but not in the sterol esters. These increases occurred chiefly at the expense of C18:1omega9 and, in particular, C18:2omega6, which indicates a replacement of omega6 by omega3 acids. Long-chain monoenoic acids which are abundant in the mackerel were not detected in any serum lipid fraction.

In a study with 52 healthy volunteers, the effect of different amounts of omega 3 fatty acids on the blood lipid composition was investigated. Doses of 1.4, 2.3, 4.1, and 8.2 g of omega 3 fatty acids were administered to these subjects daily over a period of 4 wk. Total cholesterol, high-density lipoprotein cholesterol, total triglycerides, and glucose were determined in blood serum and hemoglobin in whole blood in all individuals before, during, and after the intake of omega 3 fatty acids. In pooled serum samples, the lipoprotein composition and the fatty acid composition of blood lipids were determined. All dosages caused a shift in the fatty acid composition of blood serum lipids in a favor of omega 3 fatty acids and at the expense of omega 6 and/or omega 9 acids. In the sterol esters, only the percentage of C20:5 omega 3 increased. Maximum shifts depended on the amount of omega 3 acids ingested and were evident within 1 to 2 wk. Two wk after the last ingestion of omega 3 acids, the fatty acid composition of blood serum lipids had returned to the original state. In the groups receiving 8.2 of omega 3 fatty acids, there was a significant decrease in serum triglyceride and very low-density lipoprotein levels, which is in accord with earlier observations. In the other parameters, including cholesterol and high-density lipoprotein cholesterol, no decrease or increase was observed.

A feeding experiment was carried out in which piglets were fed to a diet enriched with either mackerel oil or olive oil. The oil consumption amounted to about 100 g per animal per day. The aim of this experiment was to study the effect of feeding high amounts of fish oil rich in polyunsaturated and long-chain monoenoic acids in order to determine if any morbid changes occurred in the animals as a result of this addition. The piglets fed olive oil served as controls. After 4 weeks, blood hemoglobin, plasma glucose, and serum triglycerides were significantly lower in the mackerel oil group as compared with the control group. There was no difference in serum cholesterol and serum lipid composition. Very low density lipoproteins were lower in the mackerel oil group. The fatty acid composition of blood serum, heart muscle, and liver showed considerable differences, omega3 acids being higher and both omega6 and omega9 acids being lower in the mackerel oil group than in the control group. Some increase in the amount of triglycerides in the heart muscle was observed in the mackerel oil group. Some characteristics of "yellow fat disease" developed in the mackerel oil group. This type of vitamin E deficiency seems to be the result of the considerable amount of omega3 fatty acids present in the mackerel oil. No clinical symptoms due to ingestion of long-chain monoenoic acids were observed.

Results are presented following 119 curative resections for rectal cancer performed on 47 women and 72 men. Throughout the study it was policy to remove part of the female genital tract when the rectal tumour impinged on the uterus and/or the posterior vaginal wall. After a median follow-up of 7.5 years, local recurrence occurred in three of 46 women and 15 of 71 men (P = 0.03). The survival rates at 5 years were 71 per cent for women (95 per cent confidence interval 56-83 per cent) and 60 per cent for men (95 per cent confidence interval 50-71 per cent) (P < 0.05). The risk for distant metastasis was comparable, suggesting an influence of local recurrence on survival. Reduction of the local recurrence rate coincides with the higher proportion of anterior extensions of surgery in women (19 of 47) than in men (two of 72).