Hydrogenation is a process by which hydrogen gas is passed over polyunsaturated fatty acids in order to cause saturation of all carbon molecules. This process results in the production of a cheap source of saturated fatty acids that can be used in the manufacture of foods. Partial hydrogenation is also used in food manufacture, in particular the production of margarines and vegetable spreads. Partial hydrogenation does not saturate all of the carbon atoms, and as a result some polyunsaturated fatty acids form intermediate compounds with rotated bond angles from the natural cis to the synthetic trans form. Consumption of such trans fatty acids from foods containing vegetable spread and margarines is concerning because of a growing body of research that shows they deleteriously affect human health. In particular, consumption may lead to metabolic dysfunction by interfering with normal essential fatty acid metabolism.
That trans fatty acids can detrimentally affect normal metabolic regulation was demonstrated in a study published in the American Journal of Clinical Nutrition in 20121. The meta-analysis included 7 studies that investigated the effects of trans fatty acids on glucose regulation, where secondary outcomes were changes to plasma lipid metabolism. Although the authors found no evidence of trans fatty acids affecting blood glucose concentrations, as intake of trans fatty acids increased there was a significant decrease in high density lipoprotein (HDL) and a significant increase in low density lipoprotein (LDL). These data support findings from previous meta-analyses investigating the effects of trans fatty acids on blood lipids. Because trans fatty acids can interfere with other fatty acids during metabolic regulation, trans fats should be eliminated from the diet. In fact there is no known safe level of ingestion of trans fatty acids.
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