Polyunsaturated fatty acids, inflammatory processes and inflammatory bowel diseases

Long-term feeding of the cis-9,trans-11 isomer of conjugated linoleic acid reinforces the specific immune response in rats

Several effects on the immune system have been ascribed to the cis9,trans11 conjugated linoleic acid (CLA) isomer. We studied whether feeding a diet enriched with an 80:20 CLA isomer mix of cis9,trans11 and trans10,cis12 CLA from gestation to adulthood affects the capacity of adult rats to achieve a specific immune response. Pregnant Wistar rats were fed a 1% CLA diet or a control diet beginning on d 7 of gestation. Weaned pups received the same diet as dams until they were 15 wk old. Rats from both groups were immunized with ovalbumin (OVA) when they were 9 wk old. Dietary CLA enhanced splenocyte OVA-specific proliferation by approximately 50% (P < 0.05) and decreased the mitogen-induced proliferative responses of these cells by approximately 10-20% (P < 0.05). The diminished splenocyte proliferative response was accompanied by a lower interleukin-2 secretion (P < 0.05). Long-term CLA supplementation did not increase serum, spleen, or mesenteric lymph node production of OVA-specific antibodies (Ab) or the number of spleen anti-OVA Ab-secreting cells. Interestingly, dietary CLA increased intestinal anti-OVA IgA production by approximately 75% (P < 0.05). In conclusion, a 1% CLA diet administered from gestation to adulthood enhanced specific systemic cell-mediated immunity as well as the mucosal IgA immune response, whereas it downregulated the polyclonal activation of the immune system. These data support the long-term effects of dietary cis9,trans11 CLA isomer on the immune system.

A prospective study of meat and fat intake in relation to small intestinal cancer

Diets high in red and processed meats are associated with carcinogenesis of the large intestine, but no prospective study has examined meat and fat intake in relation to cancer of the small intestine. We prospectively investigated meat and fat intakes, estimated from a food frequency questionnaire, in relation to small intestinal cancer among half a million men and women enrolled in the NIH-AARP Diet and Health Study. We used Cox proportional hazards regression to estimate hazard ratios (HR) and 95% confidence intervals (95% CI). During up to 8 years of follow-up, 60 adenocarcinomas and 80 carcinoid tumors of the small intestine were diagnosed. Despite slightly elevated HRs for red meat, there were no clear associations for red or processed meat intake and either adenocarcinoma or carcinoid tumors of the small intestine. In contrast, we noted a markedly elevated risk for carcinoid tumors of the small intestine with saturated fat intake in both the categorical (highest versus lowest tertile: HR, 3.18; 95% CI, 1.62-6.25) and continuous data (HR, 3.72; 95% CI, 1.79-7.74 for each 10-g increase in intake per 1,000 kcal). Our findings suggest that the positive associations for meat intake reported in previous case-control studies may partly be explained by saturated fat intake.

The health implications of changing linoleic acid intakes

Linoleic acid is the most prominent polyunsaturated fatty acid (PUFA) in the Western diet. It is virtually found in every food we eat and is the predominant PUFA in land-based meats, dairy, vegetables, vegetable oils, cereals, fruits, nuts, legumes, seeds and breads. Because linoleic acid is the metabolic precursor of arachidonic acid and bioactive eicosanoids derived from arachidonic acid, there is concern that dietary linoleic acid could augment tissue arachidonic acid content, eicosanoid formation and subsequently enhance the risk of and/or exacerbate conditions associated with acute and chronic diseases (i.e., cancers, cardiovascular disease, inflammation, neurological disorders, etc.). The following series of papers examines the impact of modifying dietary levels of linoleic acid on health outcomes. The authors were asked to start with current intakes of linoleic acid (adults) and determine if health outcomes would change if linoleic acid intake increased or decreased. The authors addressed changes in tissue arachidonic acid content and eicosanoid formation, cardiovascular disease, inflammation, and psychiatric disorders.