Hippocrates’ prescription for his patients who suffered abdominal pains was simple: “Let them eat flax!” And it’s probably not bad advice—as long as the pain stems from constipation. It turns out that flaxseeds, which come from the plant used to make linen, are an excellent source of dietary fiber. This indigestible plant component provides a laxative effect by allowing wastes to absorb water as they journey through the digestive tract. But modern science suggests that eating flax may do more than increase the frequency of bathroom visits. How about decreasing the risk of heart disease and cancer? Could Charlemagne really have been on to something when, in the eighth century, he decreed that his subjects should consume flax regularly? It seems so.
Let’s begin our story in an unusual place. The barnyard! Not any old barnyard, mind you, but one where the chickens dine on flaxseeds instead of the usual chicken feed. Why? Because some egg producers are trying to improve the nutritional value and the public image of eggs. Let’s face it, when “eggs” are mentioned, the first word that often comes to mind is “cholesterol,” which in turn conjures up thoughts of clogged arteries and premature demise. In truth, blood cholesterol responds much more to the saturated fats found in meat and full-fat dairy products than it does to cholesterol in egg yolk. Still, eggs suffer from an image problem. Omega-3 fats, on the other hand, positively bask in the limelight these days. Found mostly in fish, these fats have been linked with a reduced risk of heart disease, breast cancer, inflammatory bowel disease, Alzheimer’s disease, and arthritis. Slipping these fats into eggs would certainly be a healthy boost to their image! Especially considering that many people worry about pollutants like mercury and PCBs, both of which crop up in fish.
Flaxseed is one of the few plant sources high in omega-3 fats. The term “omega-3” refers to the molecular structure of these fats, indicating the presence of a carbon-carbon double bond on the third carbon from the end of the molecule. Alpha-linolenic acid (ALA), the specific omega-3 found in flaxseed, differs slightly from eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), which are the major fats in fish, but some ALA is converted to EPA and DHA in the human body, as well as in the chicken body.
Most research has focused on the health benefits of EPA and DHA, but ALA itself has also been linked with a reduced risk of heart disease. The Nurses’ Health Study, monitored by Harvard University researchers, has followed the health status of over 75,000 nurses who, starting in 1984, filled out food questionnaires every four years. Women who consumed the most alpha-linolenic acid from foods had a 46 percent lower risk of sudden cardiac death than women who consumed the least. The major sources of ALA were green leafy vegetables, walnuts, canola oil, and flax.
Canadian guidelines recommend 1.1 grams of omega-3s for women and 1.5 grams for men on a daily basis. These are really no more than educated guesses based on studies carried out mostly with fish oils. A British trial, for example, showed that heart patients advised to eat two servings of oily fish a week, or to take daily fish oil capsules for two years, had a significantly lower death rate than patients who were told to increase their fiber intake and reduce fat consumption. An Italian study of over 2,800 heart-attack survivors also showed that fish oil capsules providing 850 milligrams each of EPA and DHA dramatically reduced the incidence of death in the first nine months following a heart attack. The protection, however, seems to fade with time, even if fish oil consumption is maintained.
Where do omega-3 eggs fit into this picture? Feeding flax-seeds to chickens makes great use of the “you are what you eat” phenomenon, and results in eggs that have roughly twelve times more omega-3 fats than regular eggs. Of course, the important question is whether eating such eggs makes a significant contribution of omega-3s to the diet. Perhaps surprisingly, it does. Each egg has roughly 0.35 grams of ALA and 0.13 grams of EPA and DHA, so a couple of eggs provide a significant portion of the recommended intake, about the same as a couple of ounces of a high-oil fish, like salmon. No nutritional authorities suggest that we should be eating two eggs every day, but five to seven a week is reasonable. And even at that rate, switching to omega-3 eggs makes sense. This is roughly equivalent to a weekly serving of fish.
By now you’re thinking that this must be too good to be true. There must be a “but” coming up, right? Right! Back in 1994, the scientific community was stunned by a study that linked high blood levels of alpha-linolenic acid with an increased risk of prostate cancer. Total fat consumption had been associated with this cancer before. That was no great surprise, since dietary fat is known to increase the production of male sex hormones, which are linked to prostate cancer. Furthermore, many pesticides are fat soluble, and a high-fat diet increases the body’s pesticide load, which is certainly undesirable. But all previous indications had been that a diet high in fish oils decreases the risk of prostate cancer. Could ALA be different from other omega-3s? Was it protecting the heart while increasing the risk for prostate cancer? Several studies since have also suggested that ALA may be linked to prostate cancer, but there is considerable controversy surrounding the issue. Plasma levels of ala, for example, show no association with ALA levels in tissue taken from prostate cancer patients. The prudent analysis of the data suggests that it is probably not a good idea for men to consume flax oil on a regular basis.
Ready for another “but”? Consuming flaxseeds themselves has consistently been linked to a reduced risk of both prostate cancer and breast cancer. Perhaps this is because other components of the seed, such as lignans, have proven anti-cancer properties, and may overcome any detrimental effect that may be attributed to ala. A study at Duke University clearly showed that men awaiting surgery for prostate cancer benefited from a daily consumption of three tablespoons of ground flax. Testosterone levels were lowered, and there was a decrease in cancer cell proliferation.
So we now have the following scenario. The omega-3 fat in flax protects against heart disease, probably by reducing inflammation in the arteries and by smoothing out irregular heartbeats. Flax is also an excellent source of soluble fiber, which binds bile acids in the intestinal tract. This forces the liver to make more bile acids to aid in digestion. Since the raw material for bile acid synthesis is cholesterol, flax consumption ends up lowering cholesterol levels. Soluble fiber also slows the transit time of food through the stomach and small intestine, which in turn reduces the rate at which glucose is absorbed into the bloodstream. Diabetics have seen blood glucose levels drop with increased flax intake; in one study, blood glucose levels were lowered by almost 30 percent with a daily consumption of 50 grams of flax-seed. The lignans in the seed might also have a protective effect against cancer. Certainly, the work of Drs. Lillian Thompson and Paul Goss at the University of Toronto is encouraging. These researchers showed that women awaiting surgery for breast cancer had slower-growing tumors if they ate muffins containing 25 grams of milled flaxseed on a daily basis.
Basically, then, consuming ground flaxseed in the ballpark of 25 to 50 grams a day (about 2 tablespoons) seems to be a good idea. Ground seeds can be stored in an airtight container in the refrigerator for roughly a month. Unfortunately, if the seeds are not ground, they tend to exit the body undigested. But consuming flax oil may be a different matter. For men, at least, there is that bothersome potential connection between ALA and prostate cancer.
Omega-3 fats cannot all be lumped into the same category, and it certainly appears that the health benefits of the ones found in fish oil are superior to those of the ALA in flax. Wouldn’t it be great if the ratio of ALA to DHA and EPA in flax could be altered to increase the latter? Well, it looks like genetic engineering may just deliver the goods in this instance!
Genetic modification of plants has been criticized for various reasons, including the fact that so far the consumer has seen no obvious direct benefit of the technology. Now researchers at the University of Hamburg have succeeded in modifying flax plants to produce more DHA and EPA. They managed to isolate the gene from a species of algae that codes for an enzyme that converts ALA into DHA and EPA and have introduced it into flax plants. (Fish derive their omega-3 fats from eating algae.) This will make not only for healthier flax for human consumption, but also for improved animal feed. Chickens that dine on genetically modified flaxseeds will produce eggs with a higher DHA and EPA content, and men will worry less about the alpha-linolenic acid content of flax oil. Where does this leave us? Ground flaxseed is a great addition to the diet, and may be even better when the genetically modified version becomes available.
And in addition to all this, omega-3 fats may even enhance brain function. When we are born, our brain already weighs 70 percent of its adult weight, and most of its growth is completed by about six years of age. Infants whose mothers took extra EPA and DHA during pregnancy show higher mental processing scores and eye-hand coordination at age four. Some studies also have shown a beneficial role for these fats during preschool years in terms of preventing attention deficit hyperactivity disorder and enhancing learning capability. So, like Hippocrates said, “Let them eat flax!” Chickens, and people.