Conjugated linoleic acids as functional food: an insight into their health benefits

TLDR

Conjugated linoleic acids (CLA) are a heterogeneous group of isomers studied over decades for diverse biological activities, showing potential anti‑obesity, anti‑cancer, anti‑atherogenic, anti‑diabetic, immunomodulatory, apoptotic, and bone‑forming effects, but also reported adverse outcomes such as fatty liver, colon carcinogenesis, and hyperproinsulinemia, with safety still uncertain due to variable isomer types, dosages, and demographic factors. This review evaluates the health benefits of the functional food, conjugated linoleic acids (CLA) – a heterogeneous group of positional and geometric isomers of linoleic acid predominantly found in milk, milk products, meat, and meat products of ruminants. The authors conduct a comprehensive review of CLA isomers, summarizing evidence from in vitro, animal, and human studies to assess their health effects. Current trials suggest that CLA function as a food with predominantly beneficial health effects for humans.

Abstract

This review evaluates the health benefits of the functional food, conjugated linoleic acids (CLA) - a heterogeneous group of positional and geometric isomers of linoleic acid predominantly found in milk, milk products, meat and meat products of ruminants. During the past couple of decades, hundreds of reports - principally based on in vitro, microbial, animal, and of late clinical trials on humans - have been accumulating with varying biological activities of CLA isomers. These studies highlight that CLA, apart form the classical nuclear transcription factors-mediated mechanism of action, appear to exhibit a number of inter-dependent molecular signalling pathways accounting for their reported health benefits. Such benefits relate to anti-obesitic, anti-carcinogenic, anti-atherogenic, anti-diabetagenic, immunomodulatory, apoptotic and osteosynthetic effects. On the other hand, negative effects of CLA have been reported such as fatty liver and spleen, induction of colon carcinogenesis and hyperproinsulinaemia. As far as human consumption is concerned, a definite conclusion for CLA safety has not been reached yet. Parameters such as administration of the type of CLA isomer and/or their combination with other polyunsaturated fatty acids, mode of administration (eg., as free fatty acid or its triglyceride form, liquid or solid), daily dose and duration of consumption, gender, age, or ethnic and geographical backgrounds remain to be determined. Yet, it appears from trials so far conducted that CLA are functional food having prevailing beneficial health effects for humans.