Effect of trans fatty acid isomers from ruminant sources on risk factors of cardiovascular disease: study design and rationale

Authors: Gebauer, Sarah; DESTAILLATS, FREDERICK - Nestle; Baer, David

Submitted to: Contemporary Clinical Trials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2011
Publication Date: 3/31/2011
Citation: Gebauer, S.K., Destaillats, F., Baer, D.J. 2011. Effect of trans fatty acids isomers from ruminant sources on risk factors of cardiovascular disease: study design and rationale. Contemporary Clinical Trials. 32:569-76.

Interpretive Summary: Dietary trans fatty acids come from two sources: they occur naturally in beef and dairy foods and also are formed during the partial hydrogenation of oils. Many research studies have shown that there are harmful results from eating industrially-produced trans fatty acids (TFA). The effects of naturally occurring trans fatty acids are less clear because this source of dietary trans fatty acids has not been studied as extensively. Vaccenic acid is the predominant form of trans fatty acids in naturally occurring products whereas a mixture of different trans fatty acids is produced during partial hydrogenation of oils. Thus, the current study was designed to determine whether consumption of different sources of TFA may differentially affect risk factors of cardiovascular disease (CVD). The study was a randomized, crossover design, controlled-feeding intervention. Four diets were tested: 1) a low TFA diet (base diet, 34% energy from fat; 0.1% energy from TFA), 2) base diet with vaccenic acid (3.0% energy), 3) base diet with mixed isomers from TFA from partially hydrogenated vegetable oil (3.0% energy), and 4) base diet with cis-9, trans-11 CLA (1.0% energy). The energy from TFA replaced energy from stearic acid, a saturated fatty acid that minimally effects LDL cholesterol. Volunteers were required to be between the ages of 25 and 65 years, have a body mass index between 20 and 38 kg/m2, total cholesterol < 280 mg/dl, fasting triacylglycerol < 300 mg/dl, fasting glucose < 126 mg/dl, and blood pressure < 160/100 mm Hg (controlled with certain medications). Of the 116 participants who were randomized, a total of 95 completed the intervention. Results from this study will be important in determining whether ruminant TFA and industrially-produced TFA differentially affect markers of cardiovascular risk, in the context of a highly-controlled feeding study. These data will be important to the regulatory agencies globally who are deciding how to label trans fatty acids, to consumers interested in their health, and to health care professionals seeking to provide science-based recommendations to their clients.

Technical Abstract: Substantial evidence clearly demonstrates the deleterious effects of industrially-produced trans fatty acids (TFA); however, data are lacking from large, well-controlled human feeding studies that directly compare the effects of industrially-produced and naturally-occurring TFA. The purpose of the current study is to determine whether consumption of TFA derived from different sources differentially affect risk factors of cardiovascular disease (CVD). The study was a randomized, crossover design, controlled-feeding intervention designed to compare the effects of the following diet treatments on risk factors of CVD: a low TFA diet (base diet, 34% energy from fat; 0.1% energy from TFA), base diet with vaccenic acid (3.0% energy), base diet with mixed isomers from TFA from partially hydrogenated vegetable oil (3.0% energy), and base diet with cis-9, trans-11 CLA (1.0% energy). The energy from TFA replaced energy from stearic acid. Participants were required to be between the ages of 25 and 65 years, have a body mass index between 20 and 38 kg/m2, total cholesterol < 280 mg/dl, fasting triacylglycerol < 300 mg/dl, fasting glucose < 126 mg/dl, and blood pressure < 160/100 mm Hg (controlled with certain medications). Of the 116 participants who were randomized, a total of 95 completed the intervention. Results from this study will be important in determining whether ruminant TFA and industrially-produced TFA differentially affect markers of cardiovascular risk, in the context of a highly-controlled feeding study.