Omega-6 fatty acids — found in vegetable oils, nuts, and seeds, among other things — may prolong our lives.
Scientists from the University of Eastern Finland analyzed data from a study that followed nearly 2,500 men for over 20 years.
It was revealed that higher blood levels of the omega-6 fatty acid linoleic acid were tied to both a lower risk of death and death from cardiovascular disease.
"Linoleic acid," claims first author Jyrki Virtanen, an adjunct professor of nutritional epidemiology, "is the most common polyunsaturated omega-6 fatty acid."
He and his colleagues report their findings in The American Journal of Clinical Nutrition.
Omega-6 fatty acids are a group of polyunsaturated fatty acids that are present in plant-based foods such as vegetable oils, seeds, nuts, beans, and grains.
They get their name from the fact that their first double bond occurs at the sixth carbon-carbon bond counting from the methyl end (CH3) of their hydrocarbon backbone.
The debate about the benefits of omega-6
There is currently much debate about the health benefits of omega-6 fatty acids. Although widely praised for their effect on cholesterol levels, they have come under fire because it is thought that they may also do harm — such as promote low-level inflammation, which is associated with cardiovascular disease.
The reason behind this thinking lies in the fact that our bodies convert dietary linoleic acid into another omega-6 fatty acid called arachidonic acid, which, in turn, is used to make certain pro-inflammatory compounds.
Unlike linoleic acid, blood levels of arachidonic acid are not diet-dependent.
However, the notion that a diet high in omega-6 fatty acids such as linoleic acid raises disease risk by promoting inflammation ignores the fact that omega-6 fatty acids also promote anti-inflammatory compounds.
Prof. Virtanen and colleagues suggest that the controversy highlights the sorts of problems that arise when scientists focus only on the links between diet and disease risk.
Higher blood linoleic acid, lower death risk
For their research, the scientists used data from the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study.
The KIHD Study is a large, ongoing study of cardiovascular risk that follows a population of middle-aged men living in eastern Finland. Men in this region have high recorded rates of coronary heart disease.
The study data include the blood levels of fatty acids in 2,480 men who were 42–60 years of age when they joined the cohort in 1984–1989.
The men were followed for an average of 22 years, during which 1,143 of them died from causes that were disease-related. The analysis excluded men who had died from other causes such as accidents.
For their analysis, the researchers put the men in five groups ranked according to their blood level of linoleic acid, and they then compared the rates of death in the five groups.
They found that the group with the highest blood levels of linoleic acid had a 43 percent lower risk of death than the group with the lowest levels.
A more in-depth analysis revealed a similar pattern for deaths that were caused by cardiovascular disease, and also for deaths due to causes other than cardiovascular disease or cancer.
However, no such pattern was found for deaths due to cancer alone.
Similar, weaker pattern for arachidonic acid
These findings are consistent with those of other studies that followed large groups and found links between high dietary and blood levels of linoleic acid and reduced risk of diseases such as type 2 diabetes and cardiovascular disease, while not raising the risk of cancer.
When they ran their analyses again, this time using only blood levels of arachidonic acid, Prof. Virtanen and colleagues found similar but weaker patterns.
This result is a new and unique contribution of their study, they note, and they now call for further studies to confirm that higher blood arachidonic acid is linked to a lower risk of death.
The researchers also note another important finding: this was that, regardless of whether the men that they studied had cancer, diabetes, or cardiovascular disease when they enrolled in the study, the results were largely the same.
"We discovered that the higher the blood linoleic acid level, the smaller the risk of premature death."
Prof. Jyrki Virtanen