Analysis of data from 30 studies finds linoleic acid cuts CVD risk

By Hank Schultz

- Last updated on GMT

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Getty Images
A study published in a major journal shows a cardioprotective role for linoleic acid, an omega-6 fatty acid, further complicating the message about the role of fats in the diet.

Omega-6s have gotten a bad rap in recent years, especially in their role as part of the omega-6 to omega-3 ratio. It has been thought that having too much omega-6 in this calculation equates to a higher level of cardiovascular disease risk.

Fallacy of the omega-6 to omega-3 ratio

The picture is not so simple, said prominent omega-3s researcher William Harris, PhD, who is a professor at the Sanford School of Medicine. Harris is also president of OmegaQuant, an omega-3s testing firm. Harris is one of the coauthors on the recent paper, along with many other researchers.

“You can have a high amount of both omega-6 and omega-3 in your diet and your blood, or a low amount and still have the same ratio,”​ he said. “It’s not that our omega-6s are too high; it’s that our omega-3s are too low.”

Data from 69,000 participants

The paper, titled “Biomarkers of Dietary Omega-6 Fatty Acids and Incident Cardiovascular Disease and Mortality: An Individual-Level Pooled Analysis of 30 Cohort Studies,”​ was published online last week by the journal Circulation​. The study lists 58 co-authors from Asia, Australia, Europe and North America.

The researchers performed a complex statistical harmonization procedure on the data gleaned from the 30 cohort studies. Taken together, the 30 cohort studies had time frames ranging from two and a half to almost 32 years and included almost 69,000 participants. Among those subjects, slightly more than 15,000 cardiovascular events occurred.

Linoleic acid found to have cardioprotective role

After the data pooling and harmonization, the researchers came up with what to some seems a surprising conclusion.

Higher levels of LA (linoleic acid) were significantly associated with lower risks of total CVD, CV mortality, and ischemic stroke,” ​they wrote.

The result for the other omega-6 fatty acid they specifically looked for in the data from the cohort studies, arachidonic acid (AA), was also something of a surprise.

“AA levels were not associated with higher risk of cardiovascular outcomes,”​ they wrote.

Taken together, the results of the study seem to indicate that these omega-6 fatty acids, which are found in vegetable oils and other sources, ought to be chalked into the column of ‘good fats.’

“In pooled global analyses, higher in vivo levels of LA and possibly AA were associated with lower risk of major cardiovascular events. These results support a favorable role for LA in CVD prevention,”​ they wrote.

Easy answers often aren’t good answers

Harris said the search for easy answers in nutrition is seductive. “Fat is bad”​ is one of those easy answers. While it may be true that strictly limiting the intake of saturated or trans fats is a good idea, the blanket statement is not generally helpful in understanding the role of macronutrients in the diet.

“In the case of the omega-6 to omega-3 ratio, I don’t think there is an ideal ratio. One famous quote in lipids research says this ratio is ‘good divided by good,’”​ Harris said.

Harris said the picture is also more complicated than just following a fat source to the first metabolic step in the body and making a judgement based on what takes place there. The body’s inflammatory response is multi faceted and doesn’t yield easily to a simplistic analysis.

“There are people in the omega-3s camp who hate omega-6s and think they’re causing a lot of disease because they are pro inflammatory, just because they give rise to some inflammatory molecules, which we know is true. But we have also known for a long time that eating vegetable oils can lower cholesterol and lower the risk of cardiovascular disease,”​ he said.

“The counter argument is that you have to actually look at data like this that is finally coming out and you have to follow where that data takes you,”​ he said.

“Circulating and adipose tissue biomarkers of dietary omega-6 fatty acids and incident cardiovascular disease and mortality: an individual-level pooled analysis of 30 cohort studies”
2019 Apr 11. doi: 10.1161/CIRCULATIONAHA.118.038908. [Epub ahead of print]
Authors: Marklund M, et al.

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