Effects of Ruminant trans Fatty Acids on Cardiovascular Disease and Cancer: A Comprehensive Review of Epidemiological, Clinical, and Mechanistic Studies

Abstract

There are 2 predominant sources of dietary trans fatty acids (TFA) in the food supply, those formed during the industrial partial hydrogenation of vegetable oils (iTFA) and those formed by biohydrogenation in ruminants (rTFA), including vaccenic acid (VA) and the naturally occurring isomer of conjugated linoleic acid, cis-9, trans-11 CLA (c9,t11-CLA). The objective of this review is to evaluate the evidence base from epidemiological and clinical studies to determine whether intake of rTFA isomers, specifically VA and c9,t11-CLA, differentially affects risk of cardiovascular disease (CVD) and cancer compared with iTFA. In addition, animal and cell culture studies are reviewed to explore potential pro- and antiatherogenic mechanisms of VA and c9,t11-CLA. Some epidemiological studies suggest that a positive association with coronary heart disease risk exists between only iTFA isomers and not rTFA isomers. Small clinical studies have been conducted to establish cause-and-effect relationships between these different sources of TFA and biomarkers or risk factors of CVD with inconclusive results. The lack of detection of treatment effects reported in some studies may be due to insufficient statistical power. Many studies have used doses of rTFA that are not realistically attainable via diet; thus, further clinical studies are warranted. Associations between iTFA intake and cancer have been inconsistent, and associations between rTFA intake and cancer have not been well studied. Clinical studies have not been conducted investigating the cause-and-effect relationship between iTFA and rTFA intake and risk for cancers. Further research is needed to determine the health effects of VA and c9,t11-CLA in humans.

Differences in intramuscular fatty acid profiles amongBos indicusand crossbredBos taurus × Bos indicusbulls finished on pasture or with concentrate feed in Brazil

“…Generally, the 18:2 cis-9, trans-11 represents about 60-90% of the CLA isomers present in the IMF of ruminants (Alfaia et al 2009) and results mostly from endogenous synthesis where rumen-derived 18:1 trans-11 is converted into 18:2 cis-9, trans-11 by the action of D 9 desaturase in the muscle tissue (Corl et al 2001). Both 18:2 cis-9, trans-11 and 18:1 trans-11 have received attention in recent years because of their potential benefits for human health (Gebauer et al 2011), thus increasing their amount in ruminant meat is desirable. Ruminants fed with high forage/pasture in the diets generally have higher proportion of 18:2 cis-9, trans-11 in their lipids, and supplementing forage-based diets (but not concentrate-based diets) with unsaturated fat sources clearly increases the level of CLA in meat (Bessa et al 2005).…”

“…However, factors such as diet and genotype have a well-known effect on the amount of IMF and its fatty acid profile (Pitchford et al 2002;Gruffat et al 2013). On the contrary, some fatty acids (FA) have a beneficial role in human health, including n-3 PUFA, which reduce the incidence of heart diseases, and some specific isomers of conjugated linoleic acid (CLA), which have an inhibitor role in the development of atherosclerosis and cancer (Gebauer et al 2011). The WHO (2003) recommends that total fat, saturated fatty acids (SFA), n À 6 polyunsaturated fatty acids (PUFA), n À 3 PUFA and trans fatty acids should contribute <15-30, <10, <5-8, <1-2 and <1% of total energy intake, respectively.…”

Intake of ruminant trans fatty acids and changes in body weight and waist circumference

“…7 It has been hypothesised that R-TFA, or some specific TFA isomers, may elicit health benefits, but the evidence is weak and more studies are needed. 5,8 I-TFA intake in the Danish population has decreased from 2.2 g/day in 1992 to 0.35 g/day in 1999. 9 In 2004, Denmark imposed a restriction on the content of I-TFA in margarines and shortenings.…”

Alimentation des vaches laitières et composition en acides gras du lait

“…Dans le cas particulier des CLA, ce rapport concluait à un effet inhibiteur de la cancérogenèse mammaire voire prostatique, mais validé seulement sur l'animal de laboratoire et pour des apports sensiblement supérieurs aux apports habituels chez l'Homme. Si ces données ne permettent pas de proposer un objectif quantitatif de teneur en AG trans dans le lait de vache, la connaissance de ces teneurs et de leurs facteurs de variation peut avoir de l'importance, y compris la connaissance des facteurs de variation de l'équilibre entre différents isomères, dont les effets biologiques peuvent être différents (Gebauer et al 2011).…”