A study published in the American Journal of Clinical Nutrition has shown that a model built on the concentration of four fatty acids predicts mortality in older people at least as well as a model that uses smoking and diabetes.
A long-term cohort study
This study used data from the Framingham Offspring Cohort. This particular study measured an initial sample of 2,240 older people (average age of 65) and monitored them for eleven years in order to measure which characteristics are most likely to lead to survival or death during that timeframe.
Many of the results were unsurprising. For example, someone who was a smoker at the beginning of the study was as statistically likely to die of any cause as someone who was 4.73 years older; in other words, among this group, smoking was shown to decrease average lifespan by 4.73 years..Diabetes, another well-known risk factor, decreased average lifespan by 3.9 years. Women in this cohort live an average of 3.62 years longer than men.
Four fatty acids make a lot of difference
The surprising facts about this study were found in the bloodwork, as four fatty acids were found to predict mortality by substantial amounts. These were myristic acid, behenic acid, omega-3, and, negatively, palmitoleic acid.
Myristic acid, which is found in coconut milk, dairy, and some baked products, was shown to increase average lifespan by 1.41 years per quintile. Therefore, among this cohort, the people in the top 20% of having myristic acid in the bloodstream lived an average of 5.63 years longer than people in the bottom 20%. (The .01-year difference is due to rounding.)
Benehic acid is found in peanuts, macadamia nuts, and canola oil, but most of this fatty acid is produced in the human body. This fatty acid was shown to predict mortality by .79 years per quintile; in this study, people in the top 20% of behenic acid in their bloodstreams lived an average of 3.17 years longer than people in the bottom 20%. This is in accordance with previous research showing that behenic acid is negatively correlated with coronary heart disease .
The well-known fatty acid and commonly consumed supplement omega-3, which is most commonly found in fish, was also found to predict mortality. People in the highest quintile of omega-3 were found to live 4.74 years longer than people in the lowest quintile. Multiple possible mechanisms of action have been proposed for omega-3’s effects .
Unlike the other three, palmitoleic acid, which is found in macadamia oil, was negatively correlated with lifespan, and strongly so. People with an upper quintile of palmitoleic acid in the bloodstream were found to have a lifespan an average of 6.62 years lower than people in the lower quintile.
Levels of these four fatty acids are strongly correlated with one another, not independent. If you have beneficial levels of one, you are statistically likely to have beneficial levels of the others; therefore, it is meaningless to add together the years of lifespan associated with each fatty acid. Additionally, and as the researchers point out, this data only applies to people roughly 65 years to 76 years of age.
Building and comparing models
The researchers used their data to build models of mortality prediction. They found that, after controlling for age and sex, a model built on these four fatty acids was at least as effective a predictor of mortality as a model that only took smoking and diabetes into account. Combining smoking, diabetes, and the four fatty acids led to a predictive model that was significantly more effective than a model built only around commonly known risk factors.
It is rare to see any wide-scale study of a large human population cohort for lifespan, as it requires a tremendous amount of time and effort to get usable data. Analyzing many biomarkers of 2,240 people, and then conducting follow-up monitoring over the next 11 years, is no small feat. The Framingham Offspring Cohort has provided these and other researchers with a tremendous amount of information.
However, this study cannot and does not answer certain questions, such as why these fatty acids are so apparently important to human health. It also only establishes correlation, not the direction of causation; it is up to other studies to determine why these correlations exist.
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 Malik, V. S., Chiuve, S. E., Campos, H., Rimm, E. B., Mozaffarian, D., Hu, F. B., & Sun, Q. (2015). Circulating very-long-chain saturated fatty acids and incident coronary heart disease in US men and women. Circulation, 132(4), 260-268.
 Wu, J. H., Micha, R., & Mozaffarian, D. (2019). Dietary fats and cardiometabolic disease: mechanisms and effects on risk factors and outcomes. Nature Reviews Cardiology, 16(10), 581-601.