Nutrient - Fatty acids may affect our genes
The Western diet has changed dramatically over the past 100 years, resulting in a shift in the balance between omega-6 and omega-3 fatty acids. The current modern diet typically contains ten times or more omega-6 fatty acids than omega-3 fatty acids. Evidence suggests that the early hunter-gatherers maintained a much lower ratio of 2:1 (that is 2 parts omega-6 to one part omega-3) for about 100,000 generations!1 A lower ratio is also consumed by the few remaining isolated hunter-gatherer societies including the Nanamiut of Alaska and the Australia Aborigines that have remained into the 20th Century2 (heart disease, high cholesterol, obesity & diabetes are rare in these populations).
Why have the ratios changed so substantially?
The type of foods we now consume and changes in farming practices can help to explain the large shift in the ratios.
Omega-6 fats are found at high levels in many of the oil seed crops that we now consume and are also present in the meat of farm-reared, grain-fed livestock. But wild ruminants (i.e. deer, elk, and antelope) and grass-fed livestock have greater amounts of omega-3 fatty acids and an omega-6:omega-3 fatty acid ratio of about 2 to 1.1 Omega-3 fats are found at high levels in flax oils, fish liver oils, and cold-water fish body oils. The problem is, our modern diet is low in good sources of omega-3 fats, and very high in vegetable oils, and grain-fed beef, pork and poultry which are high in omega-6 fats (previous studies have reported ratios greater than 5:1 for the meat from grain-fed animals1).
Many scientists believe that these changes in the ratios may be responsible for the increase in inflammatory-related diseases including asthma, allergic rhinitis, diabetes, cardiovascular disease and inflammatory joint disease. One mechanism that has been proposed to explain the relationship between changes in these fatty acid ratios and increased inflammation is that omega-3 fatty acids can be converted into molecules that suppress inflammation, whereas omega-6 fatty acids are converted into inflammatory molecules. So shifting the balance of omega-6 and omega-3 fatty acids in favour of omega-6 fatty acids may result in an increase in the overall inflammatory state of the body. Omega-3 fatty acids have also been shown to enhance the production of resolvins and protectins which are two types of fats derived from omega-3 fatty acids that may help to dampen and resolve inflammation.3
A new way in which fatty acids may reduce inflammation
Researchers led by Floyd Chilton, writing in The Journal of Biological Chemistry, carried out a study to try and understand other possible ways in which changes in the ratio of these fatty acids might have an influence on inflammation.4 To do this, they took 27 healthy humans and fed them a controlled diet with a 2:1 ratio of omega-6:omega-3 fats to mimic the ancestral diet, and then measured the activity of certain genes and markers of inflammation. The research team found a significant drop in the levels of substances involved in inflammation, including PI3K proteins (these proteins have long been considered promising drug targets for the treatment of inflammatory disorders).
This is the first study in humans suggesting the possibility that the ratio of fats we eat could be affecting the activity of our genes, and that consuming a diet mimicking the omega-6:omega-3 fatty acid ratios of early humans may have an anti-inflammatory effect and help to reduce the incidence of inflammatory diseases.
1. Cordain L, Watkins BA, Florant GL, Kelher M, Rogers L, and Li Y. Fatty acid analysis of wild ruminant tissues: evolutionary implications for reducing diet-related chronic disease. EJCN 2002; 56:181-191.
2. Cordain L, Eaton SB, Brand Miller J, Mann N, and Hill K. The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. EJCN 2002; 56: S42-S52.
3. Serhan CN, Hong S, Gronert K, Colgan SP, Devchand PR, Mirick G, and Moussignac RL. Resolvins: a family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammation signals. J Exp Med 2002; 196:1025-37.
4. Weaver KL, Ivester P, Seeds M, Case LD, Arm JP, and Chilton FH. Effect of dietary fatty acids on inflammatory gene expression in healthy humans. J Biol Chem 2009; 284:15400-7.