Background: transFatty acids (TFAs) increase cardiovascular disease risk. TFAs and polyunsaturated fatty acids (PUFAs) in the food supply may be declining with reciprocal increases in cis-monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs).
Objectives: We sought to determine whether plasma 18-carbon TFA and PUFA concentrations might decrease over time and whether there might be reciprocal increases in plasma cis-MUFAs and SFAs.
Design: We studied 305 persons (171 women) taking part in Look AHEAD (Action for Health in Diabetes), a randomized trial of lifestyle intervention for weight loss to reduce major cardiovascular events in overweight and obese adults (aged 45-76 y) with type 2 diabetes who also participated in an ancillary study of oxidative stress. This study was a cross-sectional analysis of TFAs, cis-MUFAs, SFAs, and PUFAs measured in plasma before intervention (September 2002-April 2004).
Results: In a model that included demographic characteristics, plasma total fatty acid concentration, BMI, serum insulin, statin use, season, and longitudinal time trend (R(2) = 0.167, P < 0.0001), plasma TFAs decreased by 13.5%/y (95% CI: -22.7, -3.2%/y; absolute decrease 7.0 mg · L(-1) · y(-1); 95% CI: -12.5, -1.6 mg · L(-1) · y(-1); P = 0.012). This longitudinal trend was not significantly altered by further adjustment for dietary variables and physical activity. In contrast, longitudinal trends for PUFAs, cis-MUFAs, and SFAs were weak and not significant.
Conclusions: This change in plasma concentrations of TFAs is consistent with changes in fatty acid composition that food manufacturers are likely to have made to avoid declaring TFAs on food labels. Further research will be needed to determine the overall effect of these changes on cardiovascular risk. The Look AHEAD trial is registered at clinicaltrials.govas NCT00017953.