Study supports importance of cutting excessive omega-6 intake
by Craig Weatherby
A team of scientists from Massachusetts General Hospital just published the results of a singular, enlightening study that exploited the enviable metabolic attributes of some genetically engineered mice.
These animals' unique characteristics elicited strong affirmation of the anti-cancer effects of omega-3 fatty acids.
The new findings also underline the importance of ensuring a rough dietary parity between omega-3 and omega-6 fatty acids:
- Omega-3s are abundant in fish, walnuts, and flaxseed oil. The long-chain omega-3s in fish (EPA and DHA) are much more valuable than the short-chain omega-3 found in a few plant foods (ALA)
- Omega-6 fatty acids are abundant in grains, poultry, meats and common cooking oils (e.g., soy, corn, canola, cottonseed) used at home and in most packaged and restaurant foods. Olive, macadamia, and hi-oleic sunflower or hi-oleic safflower oils are much lower in omega-6 fatty acids.
The Massachusetts group sought to address what they called an important nutritional question: namely, whether the ratio of omega-6 to omega-3 fatty acids in our diets plays a substantial role in the development of tumors.
We already have considerable evidence that this ratio affects several major health conditions (See “Omega-3s Slow, Omega-6s Speed Prostate Cancer Growth,” “Omega-6 overload linked to depression,” and “New Report Finds Americans Need Far More Omega-3s”).
And the new results strengthen the case that people's fatty acid intake ratio counts for a lot in the context of cancer.
Clever study clarifies role of omega-3/omega-6 ratio in skin cancer
The Boston team used mice that were genetically engineered to convert dietary omega-6 fatty acids to omega-3 fatty acids readily: a capacity normally weak or lacking in mice and men alike.
As a result of their special, genetically conferred capacity, these particular “transgenic” mice enjoy an ideally balanced ratio of omega-6 fatty acids to omega-3 fatty acids in their tissues and organs, without regard to their dietary intake of the two essential nutrients.
As the scientists said, this characteristic “…allows carefully controlled studies to be performed in the absence of potential confounding factors of diet…”, and therefore enables researchers to gauge more accurately the importance of the dietary omega-3/omega-6 ratio in the development of tumors.
Accordingly the investigators implanted melanoma B16 skin cancer cells into the transgenic mice and also in regular, “wild-type” littermates.
Compared with their wild-type cousins, the transgenic mice displayed five beneficial outcomes, due almost certainly to their high tissue levels of omega-3s and their healthy balance of omega-6 and omega-3 fatty acids:
- Melanoma formation and growth was dramatically reduced.
- The level of omega-3 fatty acids was much higher in their tumors and surrounding tissues.
- The omega-6/omega-3 ratio in their tissues was much lower.
- The levels of prostaglandin E-3 (PGE-3)—an anti-inflammatory, anti-cancer messenger chemical generated by omega-3s—in their tissues were higher.
- A tumor suppressor gene called the “phosphatase and tensin homologue” or PTEN, was up-regulated (activated), thanks to the presence of extra prostaglandin E-3.
The significance of this study lay in its ability to use the transgenic mice to isolate the effect of high tissue levels of omega-3s and a low omega-6/omega-3 ratio on cancer development and growth.
And the lesson seems clear: get your fatty acids in balance!For most Americans, this entails cutting their omega-6 intake and raising their omega-3 consumption.
- Xia S, Lu Y, Wang J, He C, Hong S, Serhan CN, Kang JX. Melanoma growth is reduced in fat-1 transgenic mice: impact of omega-6/omega-3 essential fatty acids. Proc Natl Acad Sci U S A. 2006 Aug 15;103(33):12499-504. Epub 2006 Aug 3.
- Kang JX, Wang J, Wu L, Kang ZB. Transgenic mice: fat-1 mice convert n-6 to n-3 fatty acids.Nature. 2004 Feb 5;427(6974):504. Erratum in: Nature. 2004 Feb 19;427(6976):698.