Wednesday, September 15, 2010

New study: Omega 6, epigenetics, and obesity

Standard American Diet

The Standard American Diet (SAD) tends to be very high in linoleic acid (LA), the main polyunsaturated fatty acid (PUFA) in vegetable, grain, and seed oils. Over the last several decades a phobia of animal fats has lead food manufacturers and health authorities to replace naturally occurring animal fats with industrially processed vegetable oils in many foods. This in turn has resulted in a massive increase in omega 6 intake in humans compared to pre-industrial populations. Now research is being done that implicates omega 6's in multi-generational obesity. 

Not meant for human consumption?

Recent research has shown that a high intake of omega 6 fatty acids (polyunsaturated) causes epigenetic changes in populations increasing the risk of obesity in later generations.

A new study (1), has shown that mice exposed to a diet high in LA and low in ALA (omega 3), similar to the american diet, changes gene expression in a way that increases the prevalence of obesity. 

"To perform their experiments, the researchers exposed four generations of mice to a Western-style diet, characterized by these same omega 6/omega 3 ratios. As a result, they saw a gradual increase in fat mass over several generations. They also observed the onset of metabolic disorders such as insulin resistance, which is the first step in the development of type 2 diabetes and a stimulation of the expression of the inflammatory genes involved in obesity." (2)

In industrialized countries, the amount of ingested omega 6 has shot off the charts, increasing by 240% over the last 40 years (2). During this same period there has been a steady rise in obesity throughout multiple generations. It is now thought that this decrease in omega 3's and increase in omega 6's has serious long term effects on human health, bringing in to question the recommendation of replacing other fats (saturated) with omega 6's in the diet. 

Surprising, but not really

The recent research in to omega 6 fats goes against conventional wisdom on dietary fats, but in retrospect the poor health outcomes related to high omega 6 are not that surprising. Agriculture was developed about 10,000 years ago, and the industrial processing to render vegetable oils (omega 6) only became widely available within the last 50 years. Humans have been evolving for 2.5 million years. This means that high concentrations of grains and vegetable oils in the diet have only been possible for  .4% and .002% of our evolutionary history respectively. This is certainly not enough to permit sufficient evolutionary adaptation and it is not surprising that introducing massive amounts of these foods never seen before can negatively affect human health. 

The bottom line

The take home concept from this study is that if your grandfather ate large amounts of vegetable oil, it increases the chance that you will develop obesity. Ditch the industrially processed vegetable oils from the diet. Corn, canola, soy, and sunflower oil are destructive to humans in a variety of ways which I will be discussing in future posts.


1. Massiera et al. A Western-like fat diet is sufficient to induce a gradual enhancement in fat mass over generations. The Journal of Lipid Research, 2010; 51 (8): 2352 DOI: 10.1194/jlr.M006866

2. CNRS (2010, July 27). Excessive intake of omega 6 and deficiencies in omega 3 induce obesity down the generations. ScienceDaily. Retrieved September 15, 2010, from