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I look upon it, that he who does not mind his belly will hardly mind anything else. SAMUEL JOHNSON, 1763
THE YEAR 2003 WILL BE REMEMBERED AS A TIME WHEN AMERICA LOST its dietary senses. Overnight, it seemed, this country switched from a low-fat regime, in which people shunned every form of visible fat, to the Atkins regime, in which fat consumption was encouraged but carbohydrates were to be avoided. Jack Sprat, who could eat no fat, suddenly became Sprat's wife and could eat no lean.
The accumulated nutritional advice from decades of research was tossed aside like an old blanket, and grocery stores were suddenly filled with such gastronomical oxymora as low-carb bread and beer. Thin women in tight jeans were overheard saying that they loved beets and apples but had to stay away from them because of all their carbs. Large men in business suits ordered bunless burgers dripping with bacon grease and raved about their diets. Anyone coming back to the United States after time spent in Europe or Asia had an Alice-in-Wonderlandexperience, as several returnees told me: black had become white and carbohydrates, the food that feeds most of the world's peoples, including the world's leanest peoples, were suddenly the bad guys.
But 2003 should be remembered not only as the year that America lost its dietary senses (which it did) but also as the year that the center would no longer hold. By 2003, the nutritional advice given out to Americans by government agencies like the United States Department of Agriculture and medical organizations like the American Heart Association had become so out of sync with current research and biological understanding that schisms and confusion became inevitable.
It is unfortunate that those schisms took the form of total rejection, on the part of many Americans, of all the acquired wisdom about what constitutes a healthy diet. But that's what happens when the center doesn't hold, when the marketplace is full of such absurdities as overly sweetened breakfast cereals, such as Cocoa Puffs and Lucky Charms, being endorsed by the American Heart Association (because they have no cholesterol or saturated fat)-when the oversimplistic, low-fat mantra of the 1980s and 1990s made the Atkins craze almost inescapable. As a dieter in Texas confides, "Eating low-fat guarantees that I will binge on fried foods. Eating low-carb guarantees that I will binge on a bag of chips."
Much of the country is now on that fried-food, high-fat binge (or has binged out on Atkins and moved on). Many of us are more confused than ever about the simplest, most fundamental of questions: What should we have for dinner?
In the midst of this confusion, I'd like to throw my hat into the ring of nutritional advice with a tribute to one food, or family of foods: the fatty acids popularly known as the omega-3s. Because these fats were not recognized as being essential to human health until the 1980s, most current recommendations and nutritional advice took shape without them. At the same time, they were being eliminated from many foods because their presence caused problems with product stability and shelf life. Their absence, from our foods and our guidelines, is a key, a large and growing number of scientists believe, to many of our health problems-and even our befuddlement about food.
I have none of the usual qualifications to write this homage. I am neither a physician who treats the diseases to which people who are deficient in these fats are prone nor a scientist who has spent a lifetime researching the membranes that these fats call home. But that may be an advantage, since scientists and physicians tend to focus on the one piece of the puzzle they are looking at and these fats, as it turns out, affect the entire body in many different ways.
Rather, I am a science writer, a curious denizen of twenty-first-century America with a long-standing interest in food and the difficulties of being a human omnivore, and I will try to present the big picture. Quite simply, trying to understand health and diet without an appreciation of these fats is like trying to understand earthquakes without knowledge of plate tectonics, or motion without knowledge of physics. Until we revise our foods and guidelines to incorporate all that has been learned about omega-3 fatty acids in the past fifty years, our diet will be lacking in a very important way.
After I introduce these fats, I think you will begin to see why they deserve this book of their own. This introduction will involve some chemistry, but only what is necessary and most of which will be familiar to cooks, shoppers, and nutrition-conscious readers. Further explanations and diagrams can be found in the glossary, which begins on page 159. All that readers need to know from the get-go is that fatty acids, the components of fats and cell membranes, are chains of carbons and hydrogens with an acidic group at one end. The first of the omega-3 fatty acids is alpha linolenic acid, or ALA, the single parent of this family of fats. Found primarily in the leaves and other green parts of plants, alpha linolenic acid is the fat associated with the complex photosynthetic machinery of plants, the fat that enables plants to capture single photons of light and turn them into sugars, the basis of all life on earth. Alpha linolenic acid doesn't play a significant role in animals, for reasons I will soon discuss, but it does give rise to offspring who do work that is every bit as important to animals as photosynthesis is to plants.
Like all fatty acids, alpha linolenic acid is a weak acid-that is, it has a slight tendency to lose a hydrogen ion and develop a negative charge. It has the same strength as a very familiar acid, vinegar, which is not surprising since vinegar, or acetic acid, is also a fatty acid that is common in living tissues but too short (just two carbons long) to be of use in storing energy or building structures.
Fatty acids lose their acidic leaning when they team up with a molecule of glycerol to make triglycerides, the substances we commonly call fats (the substances we cook with and that don't mix with water). In most contexts, we can think of fatty acids and fats as equivalent terms. And we can think of the acidic end of a fatty acid as the hook, or the coupling, that enables our bodies to move these long, sticky chains of carbons and hydrogens around. It's also helpful to understand that all triglycerides have an identical glycerol backbone attached to three, often different, fatty acids, sixteen to twenty-two carbons in length.
1 glycerol + 3 fatty acids -> 1 triglyceride + 3 molecules water
Whether these triglycerides take the shape of butter, vegetable oil, lard, or suet depends entirely on which fatty acids are involved. Some fatty acids have straight, saturated chains (saturated with hydrogens, that is) and produce solid fats; others have kinky, unsaturated chains (where some of the hydrogens have been replaced by double bonds between the carbons) and produce liquids.
Alpha linolenic acid has a markedly kinky tail, and the fats in which it is abundant-linseed, canola, and soybean oils-are liquids, even at very low temperatures. But alpha linolenic acid is not kinky enough for animals, which are faster (more mobile) than plants, and animals lengthen and add double bonds to this eighteen-carbon fatty acid before they put it to work in their tissues.
Docosahexaenoic acid, or DHA, is one of several offspring of alpha linolenic acid and it is the longest, most desaturated fatty acid in animal tissues. It is the fat that permits animals to think and see. DHA is found in its highest concentrations in the membranes of the cells of the brain and eyes, where its ability to flip-flop between hundreds of different shapes, billions of times per second-the result of an extremely kinky chain with six carbon double bonds (twice as many as in alpha linolenic acid)-enables nerve cells to send their rapid signals. DHA is a quick-change artist, scientists have recently learned, and its concentrated presence in cell membranes, the thin envelopes surrounding cells, transforms those barriers from orderly guards into dancers at an all-night rave. Its dilute presence in cells throughout the body is like oil added to an engine.
Animals make very different use of a second, somewhat shorter, offspring of alpha linolenic acid: eicosapentaenoic acid. Eicosapentaenoic acid, or EPA, is one of several fatty acids, all twenty carbons long, that animal cells release from their membranes in order to communicate with each other and affect each other's behavior (fat signals instead of smoke signals). I'll talk more about these cell messengers later-how they were discovered and what kinds of reactions they produce-but the reader should know that this kind of communication is necessary in any organism with more than one cell and that eicosapentaenoic stands out as the mediator or peacemaker of these fat messengers. When this omega-3 fatty acid is released from a cell, it produces just the kind of measured reaction in its neighbors that is desirable in most family or neighborly interactions. It does not elicit the extreme reactions of other fat messengers-say, arachidonic acid, which enters the scene like a SWAT team. Sending in a SWAT team can be useful in some situations (in fighting infection, for example), but not to coordinate everyday disagreements.
The omega-3 fats are not rare in nature, as their remarkable behaviors might lead us to think. In fact, alpha linolenic acid, found in the chloroplasts of green leaves, is the most abundant fat on earth. Green leaves are not known for being fatty, high-calorie foods; but the planet has more green vegetation on it than anything else, and the small amount of fat in each leaf adds up. DHA and eicosapentaenoic acid are also common, since these offspring of alpha linolenic acid accumulate in the tissues of animals that eat green leaves, as well as in the tissues of animals that eat the animals that eat green leaves. Both DHA and eicosapentaenoic acid are also made by some aquatic plants.
But these fats have become rare in most Americans' diets, which are short on leafy greens and long on seeds and the oil from seeds, including soybeans and corn. And this rarity-this deficiency or insufficiency, as people have been calling it since the 1980s-is now being linked to a whole host of human ills. These include diseases of the brain, because of the high concentration of DHA in healthy nervous tissue, as well as heart disease, arthritis and other inflammatory diseases, certain kinds of cancers, and metabolic diseases such as obesity and diabetes, the diseases that tend to specifically plague Western populations-the diseases of civilization, as they have been called, without irony.
Scientists do not know everything there is to know about this family of fats and how their absence from the human diet causes disease-far from it. But what they do know should make physicians and government agencies sit up and take notice before uttering another word of dietary advice. It should cause a thorough reevaluation of our guidelines about fats and health. Why it hasn't is a good question and has something to do with resistance on the part of food industries (which have been removing omega-3s from foods because the many double bonds in omega-3 fats make them more easily oxidized than other fats, resulting in a shorter shelf life for the products that contain them), as well as with the complexity of the science that is involved. (Who would have ever thought that something as lumpish as fat could be so complicated?) It may also have something to do with the slow, meandering history of our understanding of these fats and with our very gradual realization that a balance of the different fats is essential for health.
Which brings me to the reason I have written this book: that the telling of this history may help us to see how omega-3s came to be eliminated from both our diets and our nutritional thinking and to discover how to put them back. A recounting of the ideas that shaped research and dominated medicine may reveal where the advice given us went wrong and give us the courage to make amends. This book is a tribute to the missing fats in our diet. It is also the history of how researchers discovered that these fats were missing-a nutritional whodunit that plays out in Greenland, Africa, and the many Western countries whose inhabitants first experienced this absence in the form of an epidemic of heart disease.
For many reasons, we have arrived at a critical time for this history. Though for decades we have been advised to consume diets that are low in cholesterol and saturated fat (avoiding foods such as butter and lard, which have a high percentage of straight, saturated chains), and though cholesterol and saturated fat have been reduced in the American diet, heart disease continues to afflict just as many Americans-and we're now facing epidemics of obesity and diabetes. Saturated fat and cholesterol were supposed to be the problem, so where did we go wrong? Why are our health woes multiplying instead of going away? Many explanations for this unhealthy trend have been proposed, including larger portion sizes, excess calories, an increase in the consumption of processed carbohydrates and trans fats, and a decrease in exercise, all of which may share some of the responsibility. But it's time we learned that certain fats-the fats in most of our foods-slow down metabolism, as researchers in Australia are finding. It's time we learned that many companies, in processing food, routinely eliminate the omega-3 fats that are important to both maintaining energy balance and protecting the heart.
A new labeling policy instituted in the United States, effective January 1, 2006, requires food producers to state the amount of trans fats in their products. Such labels are a good thing, since they will enable consumers to avoid these altered fats, which result from a hydrogenation process that makes vegetable oils more solid and stable (that is, less susceptible to oxidation). But the labels won't do much if food producers substitute fats that are just as unhealthy as trans fats, which is how the food industry seems to be handling the trans hysteria.
Excerpted from The Queen of Fats by Susan Allport Copyright © 2006 by Susan Allport. Excerpted by permission.
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|1||What's for dinner?||1|
|2||A trip to Greenland||14|
|3||How the omegas got their name||25|
|6||Tree lard and cow oil||68|
|7||The chemist in the kitchen||76|
|8||Out of Africa ...||86|
|9||... and into the membrane||96|
|10||Where have all the omega-3s gone?||103|
|11||The speed of life||120|
|12||Putting omega-3s back into your food supply||138|
|13||The proof is in the pudding||147|
Posted August 26, 2006
I read 'The Queen of Fats' yesterday all in one sitting and I adored it. Allport provides a perfectly accessible explanation of lipid biochemistry and then uses it to tell a very compelling story. A scientific page-turner with very easy-to-follow recommendations for how to improve your health.
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Posted February 7, 2010
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