Background & aims: There has been controversial evidence regarding the relationship between isomers of circulating trans-fatty acids (TFAs) and mortality. This study aimed to ascertain the relationships between plasma TFAs and overall or cause-specific mortality of the general population in two independent subsets from the US National Health and Nutrition Examination Survey (1999-2000 and 2009-2010 cycles).
Methods and results: Plasma TFA isomers (C16:1n-7t, C18:1n-7t, C18:1n-9t and C18:2n-6,9t) in 3439 adults free of cancer or severe cardiovascular disease were analyzed by gas chromatography/mass spectrometry. Overall, 259 died among 1376 individuals over a median follow-up of 15.6 years in the 1999-2000 cycle, and 105 died in the latter subset of 2063 subjects during a median of 5.9 years. Cox proportional hazards regression was conducted to estimate the hazard ratios of mortality. The main isomer of industrially derived TFAs, elaidic acid (C18:1n-9t) was considerably associated with long-term total mortality in the 1999-2000 cycle after adjusting for confounders, with a 54% increase in the top tertile compared with the bottom one. However, the association disappeared with halving C18:1n-9t by 2009-2010. In contrast, neither of the ruminant-derived TFAs (C16:1n-7t and C18:1n-7t) suggested any inverse correlations with all-cause death, mortality due to heart disease, cancer or other causes.
Conclusion: The major isomer of industrial TFAs, the higher circulating C18:1n-9t might be associated with increased long-term mortality. The associations with death risk turned slight with the reduction of TFAs consumption by half. However, dietary guidelines should rigorously identify the healthy effect of animal TFAs consumption.
Keywords: Elaidic acid; Mortality; Trans vaccenic acid; Trans-fatty acids.
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