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Metabolic effects of conjugated linoleic acid in humans: the Swedish experience. Riserus U, Smedman A, Basu S, Vessby B. Am J Clin Nutr. 2004 Jun;79(6 Suppl):1146S-1148S. PMID: 15159248 CONCLUSIONS CLA and specifically the isolated isomers are interesting model fatty acids for studies of the effects of (structural differences of) unsaturated fatty acids in humans. Today, there is no clear indication for human use of CLA concentrates. The possible importance of the small reduction of body fat after supplementation with the commercially available CLA products, without evidence of an associated improvement in the metabolic profile, has to be weighed against the apparent reduction of HDL cholesterol and an increased lipid peroxidation. The possible health consequences of prolonged treatment periods are at present unknown. Human supplementation with high doses of the trans-10,cis-12 CLA isomer should be avoided while awaiting further information on possible effects and side effects. However, it cannot be excluded that future studies could point to clinical applications, eg, as a result of antitumorigenic properties or as a tool to prevent weight gain. This possibility certainly requires more research to increase the understanding of the mechanisms behind the effects of CLA and specific CLA isomers on a molecular level. More controlled studies in defined populations are needed, as are controlled studies for comparisons of the effects of different and well-defined (mixtures of) isomers and human studies of longer duration to secure long-term effects and safety.

The effects of conjugated linoleic acid on human health-related outcomes. Tricon S, Burdge GC, Williams CM, Calder PC, Yaqoob P. Proc Nutr Soc. 2005 May;64(2):171-82. Review. PMID: 15960862 Conjugated linoleic acid (CLA) is a collective term for a mixture of positional and geometric isomers of conjugated dienoic derivatives of linoleic acid. CLA has received considerable attention as a result of animal experiments that report anti-carcinogenic, anti-atherogenic and anti-diabetic properties, and modulation of body composition and immune function. Several studies of CLA supplementation in human subjects have now been published, but in contrast to animal studies there has been marked variation between reports on the health-related outcomes. The consensus from seventeen published studies in human subjects is that CLA does not affect body weight or body composition. Some detrimental effects of the trans-10,cis-12 CLA isomer have also been reported in terms of altered blood lipid composition and impaired insulin sensitivity. Finally, CLA has only limited effects on immune functions in man. However, there have been reports of some interesting isomer-specific effects of CLA on the blood lipid profile, but not on immune function. These isomer-specific effects need further investigation. Until more is known, CLA supplementation in man should be considered with caution.

Holick, M. F., MacLaughlin, J. A. & Doppelt, S. H. (1981) Factors that influence the cutaneous photosynthesis of previtamin D3. Science 211:590-593 When human skin was exposed to simulated solar ultraviolet radiation, epidermal 7-dehydrocholesterol was converted to previtamin D3. During prolonged exposure to simulated solar ultraviolet radiation, the synthesis of previtamin D3 reached a plateau at about 10 to 15 percent of the original 7-dehydrocholesterol content, and previtamin D3 was photoisomerized to two biologically inert isomers, lumisterol3 and tachysterol3. Increases either in skin melanin concentration or in latitude necessitated increases in the exposure time to simulated solar ultraviolet radiation required to maximize the formation, but not the total content, of previtamin D3. In order of importance, the significant determinants limiting the cutaneous production of previtamin D3 are (i) photochemical regulation, (ii) pigmentation, and (iii) latitude.

Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men. Riserus U, Vessby B, Arnlov J, Basu S. Am J Clin Nutr. 2004 Aug;80(2):279-83. PMID: 15277146 CONCLUSIONS: A CLA preparation containing the purified c9,t11 CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. Because c9,t11 CLA occurs in commercial supplements as well as in the diet, the present results should be confirmed in larger studies that also include women.

Resveratrol: Isomeric Molar Absorptivities and Stability Brent C. Trela and Andrew L. Waterhouse J. Agric. Food Chem. 1996, 44, 1253-1257 Department of Viticulture and Enology, University of California, Davis, California 95616

Resveratrol: Isomeric Molar Absorptivities and Stability Brent C. Trela and Andrew L. Waterhouse J. Agric. Food Chem. 1996, 44, 1253-1257 Department of Viticulture and Enology, University of California, Davis, California 95616