"Dr. Schwarcz...has a knack for translating science into a language that anyone can understand and actually enjoy." Toronto Sun
Let Them Eat Flax!: 62 All-New Commentaries on the Science of Everyday Food & Lifeby Joe Schwarcz
Do you know if your waiter sings in the bathroom? Or if the lady who whipped up the icing on your cake wore false fingernails? When was the last time you microwaved your dishcloth? Is your orange juice pasteurized? In Let Them Eat Flax!, award-winning author Dr. Joe Schwarcz explains why these are more important questions than whether you eat fresh or farmed
Do you know if your waiter sings in the bathroom? Or if the lady who whipped up the icing on your cake wore false fingernails? When was the last time you microwaved your dishcloth? Is your orange juice pasteurized? In Let Them Eat Flax!, award-winning author Dr. Joe Schwarcz explains why these are more important questions than whether you eat fresh or farmed salmon, whether genetically modified foods should be labeled, or whether fruits and vegetables harbor traces of pesticides. In Let Them Eat Flax!, Dr. Joe Schwarcz continues his crusade against purveyors of poppycock as he investigates the surprising and sometimes sinister science of everyday food and life. What difference does an atom make? It could mean life or death! Get the lowdown on oxygenated water, the healing powers of prayer, and the health benefits of chocolate. Could there be a link between McGill University and Jack the Ripper? Find out how cinnamon helps to counter high cholesterol, and learn just how sweet sugar alternatives can be. In the tradition of Dr. Joe's five previous best-sellers, Let Them Eat Flax! fries scientific baloney with humour, wit, and information. From food poisoning to the secret of the Stradivarius violin, fertilizers to spontaneous human combustion, Dr. Joe investigates explosive subjects and delivers the unbiased, scientific facts readers need to make informed decisions in their everyday lives.
"Dr. Schwarcz...has a knack for translating science into a language that anyone can understand and actually enjoy." Toronto Sun
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Let Them Eat Flax
70 All-New Commentaries on the Science of Everyday Food & Life
By Joe Schwarcz
ECW PRESSCopyright © 2005 ECW Press
All rights reserved.
Let Them Eat Flax
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 ofALA 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, orto 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 ofALA 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 anticancer 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.CHAPTER 2
Pomegranate and Blueberry Frenzy
"How much pomegranate juice should I drink?" "How many blueberries do I have to eat to get that cholesterol down?" When I get a flurry of such questions, it usually means that a report of a legitimate scientific study has appeared in the lay press, often presenting the results in an overly optimistic light.
The pomegranate craze was sparked by a couple of studies that suggested the fruit may have a role in treating breast cancer and in lowering the risk of heart disease. By the time the tabloids got through with their interpretation of the results, pomegranate juice had become the new wonder kid on the block. And, needless to say, pomegranate capsules are now featured in health-food stores as cancer-preventatives and as treatments for menopause.
But what did the researchers really find? They discovered that there are compounds in pomegranate juice that have estrogenic activity. In other words, they can alter the way that cells respond to the body's own estrogen. This is certainly of great interest because more than two-thirds of breast cancers are estrogen positive, meaning that the body's estrogen stimulates the proliferation of tumor cells. Any substance that reduces such estrogenic stimulation is most welcome. And it seems that some of the polyphenols in pomegranate can do just that. They block the activity of an enzyme known as "aromatase," which is involved in the synthesis of estrogen. (Drugs known as "aroma-tase inhibitors" are now commonly prescribed in the treatment of some breast cancers.) How did the scientists determine the aromatase blocking activity of pomegranates? By studying the effect of the juice on breast cancer cells in the laboratory. They discovered that extracts of the seeds, which is what pomegranate juice really is, reduced the activity of 17-beta-estradiol, the estrogen of concern in breast cancer, by some 50 percent. And breast cancer cells that experienced this reduction in estrogen stimulation died with much greater frequency than normal cells. Of course, this is a laboratory finding, and is still a long way away from showing that pomegranate juice has any effect on actual cancers in the body. There is a big difference between bathing cultured cancer cells in pomegranate juice in a petri dish and drinking the juice. Nobody knows if the active ingredients can be absorbed from the digestive tract and if they have any chance of making it to the site of a tumor. But it seems a pretty good bet that pomegranate juice is not harmful, and may do some good.
Although its benefits for breast cancer may be iffy, pomegranate's role as a heart disease preventative is on firmer footing. Israeli researchers investigated the effect of pomegranate juice on LDL cholesterol or, in everyday language, "bad cholesterol." The juice reduced the conversion of LDL into its most damaging form, known as "oxidized LDL." This finding really may be more than a laboratory curiosity. Why? Because the researchers also found that when mice specially bred to develop hardened arteries were given pomegranate juice, the size of the lesions in their arteries was reduced by 44 percent. So, basically, while the hype about pomegranate juice may not be completely justified, there is something to it. A daily glass of 8 ounces just may provide surprising benefits. When ten patients with diagnosed atherosclerosis drank a daily glass of pomegranate juice for a couple of years, their blood pressure dropped by 20 percent, and they also experienced a beneficial reduction in the thickness of their carotid artery walls. These effects were not seen in subjects who consumed a placebo drink free of flavonoids, the pigments in pomegranate juice that are believed to be responsible for desirable effects. So, drink the juice, just don't spill any on your clothes. Pomegranate stains are virtually impossible to get out! Ditto for blueberry stains, which you may also have to deal with if you follow the research in that area.
We've heard before about all the good things blueberries may do for us. Anthocyanins, the pigments responsible for the distinct color of the berries, fall into a category of compounds called antioxidants, and a wealth of research suggests that these are good for us. They may discourage blood clot formation, improve night vision, slow macular degeneration, reduce the risk of cancer, and protect brain cells from aging. So far, it is this anti-aging effect that has captured the imagination of the lay press. While nobody has yet shown that humans who load up on blueberries age more slowly, there have been some intriguing rodent studies. At Tufts University in Boston, a group of elderly rats was put on a blueberry-rich diet, while another group was treated to regular laboratory food. The blueberry-treated rats improved in balance, coordination, and short-term memory.
By the time a rat is nineteen months old (equivalent to about seventy years old for a human), the time it takes them to walk a narrow rod before losing balance drops from thirteen to five seconds. But after eating blueberry extract for eight weeks, the old rats managed to keep their balance for eleven seconds! They also negotiated mazes better! This was the study that the press seized upon, and all of a sudden, blueberries were elevated to the status of a wonder food. And now, with the announcement that pterostilbene (another compound found in blueberries) may reduce cholesterol, the nutritional status of the berries has risen to even loftier heights. The truth is that the study in question was not done on humans, and not even on live animals. It was done in the laboratory, on rat liver cells. The researchers did show that pterostilbene activates a specific receptor on these cells that is linked with reducing cholesterol and triglycerides. But nobody knows if this compound, when ingested, does the same thing in a human liver, or if it even gets there. Nobody knows how many blueberries would have to be eaten to lower blood cholesterol, or indeed if they really can do this.
That doesn't mean such research is to be ignored. My guess— hopefully an educated one—is that blueberries should, as often as possible, be a part of the five to ten servings of fruits and vegetables that experts recommend we consume every day. So I'm ready to raise a glass of pomegranate juice to the researchers who have shown that there just may be something special about blueberries.
Excerpted from Let Them Eat Flax by Joe Schwarcz. Copyright © 2005 ECW Press. Excerpted by permission of ECW PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Meet the Author
Dr. Joe Schwarcz is the author of "Dr. Joe & What You Didn't Know," "The Fly in the Ointment," and "That's the Way the Cookie Crumbles." He is a professor of chemistry and the director of the Office for Science and Society at McGill University in Montreal. He lives in Montreal, Quebec.
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