Polyunsaturated fatty acids have no association with cardiovascular mortality

After adjusting for several cardiovascular risk factors, researchers found that none of the four major polyunsaturated fatty acids were associated with cardiovascular mortality in men from Sweden who enrolled in a prospective cohort study. However, linoleic acid was inversely associated with all-cause mortality.

Lead researcher David Iggman, MD, PhD, of Uppsala University in Sweden, and colleagues published their results online in JAMA Cardiology on Aug. 17.

Guidelines suggest that people eat more polyunsaturated fatty acids via nontropical vegetable oils, nuts and fish and less saturated fatty acids via animal sources, according to the researchers. Still, they mentioned that only a few randomized trials have evaluated dietary polyunsaturated fatty acids and mortality

This trial, known as ULSAM (Uppsala Longitudinal Study of Adult Men), investigated the causes of cardiovascular disease in middle-aged men. The analysis took place in 2015 and included men who enrolled from 1991 to 1995. The researchers examined death registries through Dec. 30, 2011.

The 853 men in the study had adipose tissue biopsy specimens take from the outer quadrant of their buttocks and had their fatty acid composition analyzed by gas-liquid chromatography.

The researchers examined the following four polyunsaturated fatty acids: linoleic acid, α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid.

After a median follow-up period of 14.8 years, there were 605 deaths, including 251 cardiovascular deaths. After adjusting for cardiovascular risk factors, there were no significant associations with cardiovascular mortality.

A minimally adjusted model found that stearic acid was associated with decreased cardiovascular mortality and arachidonic acid was associated with increased cardiovascular mortality. In addition, linoleic acid was associated with decreased mortality in both models.

“Considering that [linoleic acid] is an essential fatty acid and one of the best biomarkers for n-6 [polyunsaturated fatty acid] intake, the results may suggest a beneficial role of [polyunsaturated fatty acid]-rich vegetable oils,” the researchers wrote. “Such a possibility is further supported by a current strong association between [linoleic acid] intake and adipose tissue [linoleic acid] percentage.”

The researchers cited a few limitations of the study, including its observational design, which could lead to residual confounding. Thus, they said that causality could not be implied based on the study’s results.

They also mentioned there were relatively few cardiovascular deaths and that the study had limited power to detect strong associations with fatty acids. In addition, the study only included men, so the findings might not be generalizable to women or other populations.

“A [linoleic acid] intake of less than approximately 4 percent of energy in this population seemed to have increased mortality,” the researchers wrote. “Specific dietary recommendations cannot be given, because no randomized trials have linked dietary modification of adipose tissue fatty acid composition with outcomes. … Further studies should investigate the role of dietary [polyunsaturated fatty acids] as well as adipose tissue desaturation in longevity.”