PART 6: Dose and Effectiveness

Taken together, what do these studies say about the health value and future of CLA? It seems that CLA is highly over-rated in terms of its human health benefits. More sizzle than steak, as the saying goes. There are several kinds of possibly serious negative side effects from the use of CLA that should not be ignored. These negative effects are found mainly in animals, and accompany the use of doses substantially higher than those used in humans.

At the doses used in humans, the research results are quite disappointing. Most human studies find no benefits in the degenerative conditions for which CLA is recommended: weight loss, immune function, cardiovascular problems, and antioxidant functions. The usual doses of CLA used in animals greatly exceed those used in human studies. This may explain why animal studies come up with better results than human studies, and my also explain the negative effects of CLA on liver and insulin in rats, and the changes in yolk quality and hatchability in eggs. So there appears to be a dose-related shadow side to CLA. Remove the shadow by lowering the dose, and the benefits also disappear.

If the Results are Mediocre, what Drives CLA promotion?   What drives CLA promation is obviously profit.  Cheap sunflower oil can be sold at retail for about $150 per pound. In comparison, a pound of Udo's Choice Oil Blend™, which contains about 75% undamaged EFAs (50% omega-3), retails for about $20.

Natural Sources of CLA:  Cream, nature's richest natural source of CLA, contains 5mg/gram (0.5%) of fat. The dairy isomer of CLA is mostly c9,t11-18:2. That much is apparently safe and desirable for calves. That much CLA in butter is probably safe for humans as well. At 0.5% CLA, a tablespoon (14 grams) of butter provides about 70mg of CLA. To get 3 grams of CLA from butter, one would need to eat more than 40 tablespoons of it, which is 560 grams of 1.25 pounds of butter. That's a lot more than can be recommended, even if EFA intake is optimal (about 1 tablespoon/body weight in winter; less in summer), the level that makes skin soft and velvety (more in winter, less in summer). By the way, 560 grams of butter is 560 x 0.8 (butter is 20% water) x 9 (calories per gram) = 4,032 calories.

Butter, nature's richest source of CLA, does not provide any creature with very much of it. This may explain why high levels result in disturbing negative (side) effects. In commercial preparations, the c9, t11- isomer is found mixed with large amounts of the t10, c12-18:2 (the letter "t" before the number "10" means: "trans") isomer, along with smaller amounts of the other six CLA isomers. Each of these has different properties and will therefore have different effects on cell and tissue biochemistry. The specific effects of all isomers are not yet known, but need to be known before safe recommendations for this new mixture of CLA isomers is recommended for health.

Commercial preparations also differ from one another in the relative amounts of the different isomers they contain. According to tests that have been carried out, they even differ from batch to batch. Therefore research done on one commercial CLA preparation cannot be automatically transferred to another.

This point, conveniently overlooked by manufacturers, is unknown to most consumers. To effectively treat human diseases, for which CLA showed benefits in animals, larger doses would be needed. Instead of 3 grams/day, on which we based out calculations above, and which is already very high when compared to what butter (the richest natural source) could supply, CLA doses would need to be even higher.