Just the flax

“Research has huge gray areas which require further research for definition.”

This observation comes from an HSI member named Brian who sent me an e-mail a few days ago, inquiring about flaxseed. Specifically, Brian asked me to address some contradictory information that he’d come across from different sources associated with HSI’s parent company. And it’s no wonder that Brian and others are confused, because flaxseed and flaxseed oil are at the center of a debate that still has plenty of those “huge gray areas.”

Nevertheless, I think a closer look at what we do know can dispel some of the gray and bring the flax picture into better focus.

In September I sent you an e-Alert (“What the Squeaky Wheel Gets” 9/18/02) that examined the dietary importance of maintaining a proper balance of the two groups of essential fatty acids: omega-6 and omega-3. Nutritionists generally agree that the optimal balance of these two should be 1:1, or at least close to that. Most diets, however, are high in omega-6 (readily available in the oils used in many processed foods) and low in omega-3. The most common dietary source of omega-3 is fish, especially dark-meat fish like swordfish and tuna. To avoid mercury, a high quality fish oil supplement is a good source as well. And here is where flax makes its appearance.

Flaxseed contains lignans, a fiber and phytoestrogen with a chemical makeup similar to human estrogen. Lignans are also a good source of alpha-linolenic acid, which is converted by the body into omega-3 fatty acids, which improve cell function in the lining of the heart and blood vessels, lower triglyceride levels, and inhibit platelet clumping. And because lignans are believed to help remove testosterone from the body, they may assist in suppressing the growth of prostate cancer cells.

“Lignans are thought to be the active agents responsible for stopping growth of prostate cancers in the Duke University study of 2001.”

This comment came from an HSI member named Rick. And he’s right – last year’s Duke research did show strong indications that flaxseed may be effective against prostate cancer – especially in the development of the cancer in the early stages. But the study was relatively small (only 25 men), and brief (only 34 days). And while the positive effect on several markers associated with prostate cancer was described as significant, the study was designed to examine the combined effects of flaxseed and a low-fat diet. In other words: we have yet to see a sizeable study of extended length that judges whole flaxseed alone. So while we don’t yet have overwhelming evidence that flaxseed helps prevent prostate cancer, there are promising signs that this evidence is emerging. Meanwhile, we have to acknowledge the ironic prospect that flaxseed OIL (not flaxseeds, but the oil) may in fact promote the spread of prostate cancer cells.

The valuable lignans in flaxseed are found in the outer shell of the seeds. But when the seeds are refined into oil, only a trace of the lignans ends up in the finished product. This same process dramatically increases the concentration of alpha-linolenic acid (ALA), one of the primary omega-3 fatty acids. And while some studies have suggested that ALA may slow cancerous growth in the breast and colon, the effect on prostate cancer is an entirely different story.

Out of six known studies that have examined the association between the risk of prostate cancer and the intake of dietary alpha-linolenic acid, five of them found the cancer risk to increase with greater intake of ALA. And the most recent of these studies – a trial from the Registro Nacional de Cancer, Montevideo, Uruguay – concluded that the two major risk factors associated with prostate cancer are a family history of prostate cancer and intake of alpha-linolenic acid.

Do you ingest ALA when you eat flaxseeds? Yes, but compared to the ALA content of flaxseed oil, the ALA in the seeds is generally considered too low to be harmful to prostate cancer patients.

To say the jury is still out on the effects of flaxseed and flaxseed oil on prostate cancer is an understatement. But further studies are now in the works and, as they’re reported, the huge gray areas in this field of study will come into clearer focus.

To Your Good Health,

Jenny Thompson
Health Sciences Institute