Conjugated linoleic acid is both a trans fatty acid and a cis fatty acid. The cis bond causes a lower melting point and ostensibly also the observed beneficial health effects. Unlike other trans fatty acids, it is not harmful, but beneficial. CLA is conjugated, and in the United States, trans linkages in a conjugated system are not counted as trans fats for the purposes of nutritional regulations and labeling. CLA and some trans isomers of oleic acid are produced by microorganisms in the rumens of ruminants. Non-ruminants, including humans, produce certain isomers of CLA from trans isomers of oleic acid, such as vaccenic acid, which is converted to CLA by delta-9-desaturase.
A European team led by the Swiss scientist Lukas Rist has found that mothers consuming mostly organic milk and meat products have about 50 percent higher levels of rumenic acid in their breast milk.
Studies of CLA in human diets show that it tends to reduce body fat, particularly abdominal fat, improves serum lipid profiles, and decreases whole-body glucose uptake. The maximum reduction in body fat was achieved with a daily dose of 3.4g. CLA supplementation has, however, been shown to increase C-reactive protein levels, possibly to induce oxidative stress, to reduce insulin sensitivity, and to increase lipid peroxidation. However, the significance of these findings is unknown, and other studies suggest that CLA may protect cells from oxidative damage by increasing glutathione levels without inducing lipid peroxidation. It is possible, however, that the observation of markers of increased lipid oxidation may indicate potentially desirable lipolytic effects. Further studies are necessary to establish the clinical significance of such observations.
In one study CLA produced a 32% increase in biliary cholesterol concentration which increases the chance of gallstone formation.
In 2006, a study by the US Department of Agriculture suggested that CLA can induce essential fatty acid redistribution in mice. Changes in docosahexaenoic acid (DHA) and arachidonic acid (AA) levels were observed in some organs. For instance, certain CLA isomers reduced the DHA content of heart tissue by 25%, while in the spleen, DHA content rose, and AA fell. A study of CLA supplementation in hatchling chicks (2005) showed high mortality and low hatchability rates among CLA-supplemented groups, and also a decrease in brain DHA levels of CLA-treated chicks These studies raise the question of whether CLA may increase the risk of cardiovascular and inflammatory diseases, but it has yet to be established whether such changes occur in humans, and whether they are clinically relevant.
Eggs are also rich in CLA, and it has been shown that CLA in eggs survives the temperatures encountered during frying.
Dietary linoleic acid intake controls the arterial blood plasma concentration and the rates of growth and linoleic acid uptake and metabolism in hepatoma 7288CTC in Buffalo rats
Jul 01, 1997; ABSTRACT In this study, we tested the hypothesis that dietary linoleic acid intake controls the arterial blood plasma linoleic...
Dietary protein modifies oxidized cholesterol-induced alterations of linoleic acid and cholesterol metabolism in rats
Jun 01, 1996; ABSTRACT Effects of dietary protein on oxidized cholesterol-induced alterations in linoleic acid and cholesterol metabolism were...
Nutrients to reduce allergic symptoms: many nutrients appear to affect atopic allergic reactions. We will review some highlights from the literature.(Nutritional Influences on Illness)
May 01, 2006; Vitamins Niacin Both niacin and niacinamide inhibit mast cell degranulation and histamine release, events that promote allergic...