Effect of trans–fatty acids on lipid metabolism: Mechanisms for their adverse health effects

Partially hydrogenated oils (PHOs), the major dietary source of trans–fatty acids (TFAs), are widely used in processed foods due to their stability and desirable texture. However, scientific evidence linking TFA intake and the high risk of coronary heart diseases led the US Food and Drug Administration (FDA) to declare that PHOs could no longer be “generally recognized as safe” for use in foods. Fatty acids (FAs) are incorporated into cellular membranes, thereby altering membrane fluidity. FAs also directly bind to and modulate nuclear receptors, resulting in the regulation of gene transcription. By means of such effects, TFAs may alter the function and responses of many types of cells. TFAs may be incorporated into body lipids, oxidized, and converted into longer and more unsaturated FAs as naturally occurring cis-FAs but with different efficiency. Furthermore, they might affect the metabolism of naturally occurring cis-FAs, contributing to alteration in body FA profile. Therefore, it is important to assess their absorption, metabolism, disposition, and effect on the metabolism of other lipids to estimate their health effects. This review examines the metabolic fate of dietary TFAs. In addition, their effects on lipid and cholesterol metabolisms are discussed to elucidate the potential mechanisms involved in their adverse health effects.