Omega-3s appear to play an important role in neurological development and processing (the highest concentrations of omega-3s in humans are found in the tissues of the brain and the eyes), visual acuity (befitting their role in photosynthesis), the permeability of cell walls, the metabolism of glucose, and the calming of inflammation. Omega-6s are involved in fat storage (which is what they do for the plant), the rigidity of cell walls, clotting, and the inflammation response. It helps to think of omega-3s as fleet and flexible, omega-6s as sturdy and slow. Because the two fatty acids compete with each other for space in cell membranes and for the attention of various enzymes, the ratio between omega-3s and omega-6s, in the diet and in turn in our tissues, may matter more than the absolute quantity of either fat. So, too much omega-6 may be just as much a problem as too little omega-3.
And that might well be a problem for people eating a Western diet. As the basis of our diet has shifted from leaves to seeds, the ratio of omega-6s to omega-3s in our bodies has changed too. The same is true for most of our food animals, which industrial agriculture has taken off their accustomed diet of green plants and put on a richer diet of seeds. The result has been a marked decline in the amount of omega-3s in modern meat, dairy products, and eggs, and an increase in the amount of omega-6s. At the same time, modern food production practices have further diminished the omega-3s in our diet. Omega-3s, being less stable than omega-6s, spoil more readily, so the food industry, focused on store food, has been strongly disposed against omega-3s long before we even knew what they were. (Omega-3s weren’t recognized as essential to the human diet until the 1980s-some time after nutritionism’s blanket hostility to fat had already taken hold.) For years plant breeders have been unwittingly selecting for plants that produce fewer omega-3s, because such crops don’t spoil as quickly. (Wild greens like purslane have substantially higher levels of omega-3s than most domesticated plants.) Also, when food makers partially hydrogenate oils to render them more stable, it is the omega-3s that are eliminated. An executive from Frito-Lay told Susan Allport in no uncertain terms that because of their tendency to oxidize, omega-3s “cannot be used in processed foods.”
Most of the official nutritional advice we’ve been getting since the 1970s has, again unwittingly, helped to push omega-3s out of the diet and to elevate levels of omega-6. Besides demonizing fats in general, that advice has encouraged us to move from saturated fats of animal origin (some of which, like butter, actually contain respectable amounts of omega-3s) to seed oils, most of which are much higher in omega-6s (corn oil especially), and even more so after partial hydrogenation. The move from butter (and especially butter from pastured cows) to margarine, besides introducing trans fats to the diet, markedly increased omega-6s at the cost of omega-3s.
Thus without even realizing what we were doing, we dramatically altered the ratio of these two essential fats in our diet and our bodies, with the result that the ratio of omega-6 to omega-3 in the typical American today stands at more than 10 to 1. Before the widespread introduction of seed oils at the turn of the last century, the ratio was closer to 3 to 1.
The precise role of these lipids in human health is still not completely understood, but some researchers are convinced that these historically low levels of omega-3 (or, conversely, historically high levels of omega-6) bear responsibility for many of the chronic diseases associated with the Western diet, including heart disease and diabetes. Population studies suggest that omega-3 levels in the diet are strongly correlated with rates of heart disease, stroke, and mortality from all causes.* For example, the Japanese, who consume large amounts of omega-3s (most of it in fish), have markedly low rates of cardiovascular disease in spite of their high rates of smoking and high blood pressure. Americans consume only a third as much omega-3s as the Japanese and have nearly four times the rate of death from heart disease. But there is more than epidemiology to link omega-3 levels and heart disease: Clinical studies have found that increasing the omega-3s in one’s diet may reduce the chances of heart attack by a third.†
What biological mechanism could explain these findings? A couple of theories have emerged. Omega-3s are present in high concentrations in heart tissue where they seem to play a role in regulating heart rhythm and preventing fatal arrhythmias. Omega-3s also dampen the inflammation response, which omega-6s tend to excite. Inflammation is now believed to play an important role in cardiovascular disease as well as in a range of other disorders, including rheumatoid arthritis and Alzheimer’s. Omega-6s supply the building blocks for a class of pro-inflammatory messenger chemicals involved in the body’s rapid-response reaction to a range of problems. One of these compounds is thromboxane, which encourages blood platelets to aggregate into clots. In contrast, omega-3s slow the clotting response, which is probably why populations with particularly high levels of omega-3s, such as the Inuit, are prone to bleeding. (If there is a danger to consuming too much omega-3, bleeding is probably it.)
The hypothesis that omega-3 might protect against heart disease was inspired by studies of Greenland Eskimos, in whom omega-3 consumption is high and heart disease rare. Eskimos eating their traditional marine-based diet also don’t seem to get diabetes, and some researchers believe it is the omega-3s that protect them. Adding omega-3s to the diet of rats has been shown to protect them against insulin resistance. (The same effect has not been duplicated in humans, however.) The theory is that omega-3s increase the permeability of the cell’s membranes and its rate of metabolism. (Hummingbirds have tons of omega-3s in their cell membranes; big mammals much less.) A cell with a rapid metabolism and permeable membrane should respond particularly well to insulin, absorbing more glucose from the blood to meet its higher energy requirements. That same mechanism suggests that diets high in omega-3s might protect against obesity as well.
So why is it, as Susan Allport writes, that “populations, when given the choice, will naturally drift toward foods with lesser amounts of omega-3s”? Because a faster metabolism increases the need for food and therefore the possibility of hunger, she suggests, which is a much less agreeable condition than being overweight. This might help explain why so many groups have adopted Western diets as soon as they get the chance.
It should be said that researchers working on omega-3s can sound a bit like Dr. Casaubon in Middlemarch, hard at work on his “Key to all Mythologies.” Likewise, omega-3 researchers seem to be in possession of a Theo
ry of Everything, including happiness. The same population studies that have correlated omega-3 deficiency to cardiovascular disease have also found strong correlations between falling levels of omega-3 in the diet and rising rates of depression, suicide, and even homicide. Some researchers implicate omega-3 deficiency in learning disabilities such as attention deficit disorder as well. That omega-3s play an important role in mental function has been recognized since the 1980s, when it was found that babies fed on infant formula supplemented with omega-3s scored significantly higher on tests of both mental development and visual acuity than babies receiving formula supplemented only with omega-6.
Could it be that the problem with the Western diet is a gross deficiency in this essential nutrient? A growing number of researchers have concluded that it is, and they voice frustration that official nutritional advice has been slow to recognize the problem. To do so, of course, would mean conceding the error of past nutritional advice demonizing fats in general and promoting the switch to seed oils high in omega-6. But it seems likely that sooner or later the government will establish minimum daily requirements for omega-3 (several other governments already have) and, perhaps in time, doctors will routinely test us for omega-3 levels the way they already do for cholesterol.
Though maybe they should be testing for omega-6 levels as well, because it’s possible that is the greater problem. Omega-6s exist in a kind of zero-sum relationship with omega-3s, counteracting most of the positive effects of omega-3 throughout the body. Merely adding omega-3s to the diet-by taking supplements, say-may not do much good unless we also reduce the high levels of omega-6s that have entered the Western diet with the advent of processed foods, seed oils, and foods from animals raised on grain. Nine percent of the calories in the American diet today come from a single omega-6 fatty acid: linoleic acid, most of it from soybean oil. Some nutrition experts think that this is fine: Omega-6s, after all, are essential fatty acids too, and their rise to dietary prominence has pushed out saturated fats, usually thought to be a positive development. But others strongly disagree, contending that the unprecedented proportion of omega-6s in the Western diet is contributing to the full range of disorders involving inflammation. Joseph Hibbeln, the researcher at the National Institutes of Health who conducted population studies correlating omega-3 consumption with everything from stroke to suicide, says that the billions we spend on antiinflammatory drugs such as aspirin, ibuprofen, and acetaminophen is money spent to undo the effects of too much omega-6 in the diet. He writes, “The increases in world [omega-6] consumption over the past century may be considered a very large uncontrolled experiment that may have contributed to increased societal burdens of aggression, depression, and cardiovascular mortality.”*
Of all the changes to our food system that go under the heading “The Western Diet,” the shift from a food chain with green plants at its base to one based on seeds may be the most far reaching of all. Nutritional scientists focus on different nutrients-whether the problem with modern diets is too many refined carbohydrates, not enough good fats, too many bad fats, or a deficiency of any number of micronutrients or too many total calories. But at the root of all these biochemical changes is a single ecological change. For the shift from leaves to seeds affects much more than the levels of omega-3 and omega-6 in the body. It also helps account for the flood of refined carbohydrates in the modern diet and the drought of so many micronutrients and the surfeit of total calories. From leaves to seeds: It’s almost, if not quite, a Theory of Everything.
5) From Food Culture to Food Science
The last important change wrought by the Western diet is not, strictly speaking, ecological, at least not in any narrow sense of the word. But the industrialization of our food that we call the Western diet is systematically and deliberately undermining traditional food cultures everywhere. This may be as destructive of our health as any nutritional deficiency.
Before the modern food era-and before the rise of nutritionism-people relied for guidance about what to eat on their national or ethnic or regional cultures. We think of culture as a set of beliefs and practices to help mediate our relationship to other people, but of course culture-at least before the rise of modern science-has also played a critical role in helping to mediate people’s relationship to nature. Eating being one of the most important manifestations of that relationship, cultures have had a great deal to say about what and how and why and when and how much we should eat. Of course when it comes to food, culture is another word for mom, the figure who typically passes on the food ways of the group-food ways that endured, by the way, only because they tended to keep people healthy.
The sheer novelty and glamour of the Western diet, with its seventeen thousand new food products every year and the marketing power-thirty-two billion dollars a year-used to sell us those products, has overwhelmed the force of tradition and left us where we now find ourselves: relying on science and journalism and government and marketing to help us decide what to eat. Nutritionism, which arose to help us better deal with the problems of the Western diet, has largely been co-opted by it: used by the industry to sell more nutritionally “enhanced” processed food and to undermine further the authority of traditional food cultures that stand in the way of fast food. Industry greatly amplifies the claims of nutritional science through its advertising and, through its sponsorship of self-serving nutritional research, corrupts it.* The predictable result is the general cacophony of nutritional information ringing in our ears and the widespread confusion that has come to surround this most fundamental of creaturely activities: finding something good to eat.
You would not have bought this book and read this far into it if your food culture was intact and healthy. And while it is true that most of us unthinkingly place the authority of science above culture in all matters having to do with our health, that prejudice should at least be examined. The question we need to ask is, Are we better off with these new authorities telling us how to eat than we were with the traditional authorities they supplanted? The answer by now should be clear.
It might be argued that at this point we should simply accept that fast food is our food culture and get on with it. Over time, people will get used to eating this way, and our health will improve as we gradually adjust to the new food environment. Also, as nutritional science improves, we should be able to ameliorate the wor
st effects of this diet. Already food scientists are figuring out ways to microencapsulate omega-3s and bake them into our vitamin-fortified bread. But I’m not sure we should put our faith in food science, which so far has not served us very well, or in evolution, either.
There are a couple of problems with trying simply to get used to the Western diet. You could argue that, compared to the Aborigines, say, or Inuit, we are getting used to it-most of us don’t get quite as fat or diabetic as they do. But our “adjustment” looks much less plausible when you consider that, as mentioned, fully a quarter of all Americans suffer from metabolic syndrome, two thirds of us are overweight or obese, and diet-related diseases are already killing the majority of us. The concept of a changing food environment is not just a metaphor; nor is the idea of adapting to it. In order for natural selection to help us adapt to the Western diet, we’d have to be prepared to let those whom it sickens die. Also, many of the chronic diseases caused by the Western diet come late in life, after the childbearing years, a period of our lives in which natural selection takes no interest. Thus genes predisposing people to these conditions get passed on rather than weeded out.
In Defense of Food Page 13
