Eating in our time has gotten complicated—needlessly so, in my opinion. I will get to the“needlessly”part in a moment, but consider first thecomplexity that now attends this most basic of creaturelyactivities. Most of us have come to rely on expertsof one kind or another to tell us how to eat—doctors anddiet books, media accounts of the latest findings innutritionalscience, government advisories and foodpyramids, the proliferating health claims on foodpackages. We may not always heed these experts’ advice,but their voices are in our heads every time we orderfrom a menu or wheel down the aisle in the supermarket.Also in our heads today resides an astonishingamount of biochemistry. How odd is it that everybodynow has at least a passing acquaintance with words like“antioxidant,” “saturated fat,” “omega-3 fatty acids,”“carbohydrates,” “polyphenols,” “folic acid,” “gluten,”and “probiotics”? It’s gotten to the point where we don’tsee foods anymore but instead look right through themto the nutrients (good and bad) they contain, and ofcourse to the calories—all these invisible qualities inour food that, properly understood, supposedly holdthe secret to eating well.

But for all the scientific and pseudoscientific foodbaggage we’ve taken on in recent years, we still don’tknow what we should be eating. Should we worry moreabout the fats or the carbohydrates? Then what aboutthe “good” fats? Or the “bad” carbohydrates, like highfructosecorn syrup? How much should we be worryingabout gluten? What’s the deal with artificial sweeteners?Is it really true that this breakfast cereal willimprovemy son’s focus at school or that other cerealwill protect me from a heart attack? And when dideating a bowl of breakfast cereal become a therapeuticprocedure?

A few years ago, feeling as confused as everyoneelse, I set out to get to the bottom of a simple question:What should I eat? What do we really know about thelinks between our diet and our health? I’m not a nutritionexpert or a scientist, just a curious journalisthoping to answer a straightforward question for myselfand my family.

Most of the time when I embark on such an investigation,it quickly becomes clear that matters are muchmore complicated and ambiguous—several shadesgrayer—than I thought going in. Not this time. Thedeeper I delved into the confused and confusingthicket of nutritional science, sorting through thelong-running fats versus carbs wars, the fiber skirmishesand the raging dietary supplement debates, thesimpler the picture gradually became. I learned that infact science knows a lot less about nutrition than youwould expect—that in fact nutrition science is, to putit charitably, a very young science. It’s still trying tofigure out exactly what happens in your body when yousip a soda, or what is going on deep in the soul of acarrot to make it so good for you, or why in the worldyou have so many neurons—brain cells!—in your stomach,of all places. It’s a fascinating subject, and somedaythe field may produce definitive answers to thenutritional questions that concern us, but—as nutritioniststhemselves will tell you—they’re not there yet.Not even close. Nutrition science, which after all onlygot started less than two hundred years ago, is todayapproximately where surgery was in the year 1650—verypromising, and very interesting to watch, but are youready to let them operate on you? I think I’ll wait awhile.But if I’ve learned volumes about all we don’t knowabout nutrition, I’ve also learned a small number ofvery important things we do know about food andhealth. This is what I meant when I said the picture gotsimpler the deeper I went.

There are basically two important things you needto know about the links between diet and health, twofacts that are not in dispute. All the contending partiesin the nutrition wars agree on them. And, even moreimportant for our purposes, these facts are sturdyenough that we can build a sensible diet upon them.

Here they are:

Fact 1. Populations that eat a so-called Western diet—generally defined as a diet consisting of lots of processedfoods and meat, lots of added fat and sugar, lotsof refined grains, lots of everything except vegetables,fruits, and whole grains—invariably suffer from highrates of the so-called Western diseases: obesity, type 2diabetes, cardiovascular disease, and cancer. Virtuallyall of the obesity and type 2 diabetes, 80 percent of thecardiovascular disease, and more than a third of allcancers can be linked to this diet. Four of the top tenkillers in America are chronic diseases linked to thisdiet. The arguments in nutritional science are notabout this well-established link; rather, they are allabout identifying the culprit nutrient in the Westerndiet that might be responsible for chronic diseases. Isit the saturated fat or the refined carbohydrates or thelack of fiber or the transfats or omega-6 fatty acids—orwhat? The point is that, as eaters (if not as scientists),we know all we need to know to act: This diet, for whateverreason, is the problem.

Fact 2. Populations eating a remarkably wide rangeof traditional diets generally don’t suffer from thesechronic diseases. These diets run the gamut from onesvery high in fat (the Inuit in Greenland subsist largelyon seal blubber) to ones high in carbohydrate (CentralAmerican Indians subsist largely on maize and beans)to ones very high in protein (Masai tribesmen in Africasubsist chiefly on cattle blood, meat, and milk), to citethree rather extreme examples. But much the sameholds true for more mixed traditional diets. What thissuggests is that there is no single ideal human diet butthat the human omnivore is exquisitely adapted to awide range of different foods and a variety of differentdiets. Except, that is, for one: the relatively new (inevolutionary terms) Western diet that most of us noware eating. What an extraordinary achievement for acivilization: to have developed the one diet that reliablymakes its people sick! (While it is true that wegenerally live longer than people used to, or than peoplein some traditional cultures do, most of our addedyears owe to gains in infant mortality and child health,not diet.)

There is actually a third, very hopeful fact thatflows from these two: People who get off the Westerndiet see dramatic improvements in their health. Wehave good research to suggest that the effects of theWestern diet can be rolled back, and relatively quickly.*In one analysis, a typical American population that departedeven modestly from the Western diet (and lifestyle)could reduce its chances of getting coronaryheart disease by 80 percent, its chances of type 2 diabetesby 90 percent, and its chances of colon cancer by70 percent.*

* For a discussion of the research on the Western diet and itsalternatives see my previous book, In Defense of Food (NewYork: Penguin Press, 2008). Much of the science behind therules in this book can be found there.

Yet, oddly enough, these two (or three) sturdy factsare not the center of our nutritional research or, forthat matter, our public health campaigns around diet.Instead, the focus is on identifying the evil nutrient inthe Western diet so that food manufacturers mighttweak their products, thereby leaving the diet undisturbed,or so that pharmaceutical makers might developand sell us an antidote for it. Why? Well, there’sa lot of money in the Western diet. The more you processany food, the more profitable it becomes. The healthcareindustry makes more money treating chronicdiseases(which account for three quarters of the $2trillion plus we spend each year on health care in thiscountry) than preventing them. So we ignore the elephantin the room and focus instead on good and evilnutrients, the identities of which seem to change withevery new study. But for the Nutritional IndustrialComplex this uncertainty is not necessarily a problem,because confusion too is good business: The nutritionexperts become indispensable; the food manufacturerscan reengineer their products (and health claims)to reflect the latest findings, and those of us in themedia who follow these issues have a constant streamof new food and health stories to report. Everyone wins.Except, that is, for us eaters.

* The diet specified in this analysis is characterized by a lowintake of transfats; a high ratio of polyunsaturated fats to saturatedfats; a high whole-grain intake; two servings of fish aweek; the recommended daily allowance of folic acid; and atleast five grams of alcohol a day. The lifestyle changes includenot smoking, maintaining a body mass index (BMI) below 25,and thirty minutes a day of exercise. As the author Walter Willettwrites, “[T]he potential for disease prevention by modestdietary and lifestyle changes that are readily compatible withlife in the 21st century is enormous.” “The Pursuit of OptimalDiets: A Progress Report,” Nutritional Genomics: Discovering thePath to Personalized Nutrition, eds. Jim Kaput and Raymond L.Rodriguez (New York: John Wiley & Sons, 2006).

As a journalist I fully appreciate the value of widespreadpublic confusion: We’re in the explanationbusiness, and if the answers to the questions we exploregot too simple, we’d be out of work. Indeed, I hada deeply unsettling moment when, after spending acouple of years researching nutrition for my last book,In Defense of Food, I realized that the answer to the supposedlyincredibly complicated question of what weshould eat wasn’t so complicated after all, and in factcould be boiled down to just seven words:

Eat food. Not too much. Mostly plants.

This was the bottom line, and it was satisfying tohave found it, a piece of hard ground deep down at thebottom of the swamp of nutrition science: seven wordsof plain English, no biochemistry degree required. Butit was also somewhat alarming, because my publisherwas expecting a few thousand more words than that.Fortunately for both of us, I realized that the story ofhow so simple a question as what to eat had ever gottenso complicated was one worth telling, and that becamethe focus of that book.

The focus of this book is very different. It is muchless about theory, history, and science than it is aboutour daily lives and practice. In this short, radicallypared-down book, I unpack those seven words of adviceinto a comprehensive set of rules, or personal policies,designed to help you eat real food in moderation and,by doing so, substantially get off the Western diet. Therules are phrased in everyday language; I deliberatelyavoid the vocabulary of nutrition or biochemistry,though in most cases there is scientific research toback them up.

This book is not antiscience. To the contrary, inresearching it and vetting these rules I have made gooduse of science and scientists. But I am skeptical of a lotof what passes for nutritional science, and I believethat there are other sources of wisdom in the world andother vocabularies in which to talk intelligently aboutfood. Human beings ate well and kept themselveshealthy for millennia before nutritional science camealong to tell us how to do it; it is entirely possible to eathealthily without knowing what an antioxidant is.So whom did we rely on before the scientists (and,in turn, governments, public health organizations,and food marketers) began telling us how to eat? Werelied of course on our mothers and grandmothers andmore distant ancestors, which is another way of saying,on tradition and culture. We know there is a deepreservoirof food wisdom out there, or else humanswould not have survived and prospered to the extentwe have. This dietary wisdom is the distillation of anevolutionary process involving many people in manyplaces figuring out what keeps people healthy (andwhat doesn’t), and passing that knowledge down in theform of food habits and combinations, manners andrules and taboos, and everyday and seasonal practices,as well as memorable sayings and adages. Are thesetraditions infallible? No. There are plenty of old wives’tales about food that on inspection turn out to be littlemore than superstitions. But much of this food wisdomis worth preserving and reviving and heeding. That isexactly what this book aims to do.

Food Rules distills this body of wisdom into sixtyfoursimple rules for eating healthily and happily. Therules are framed in terms of culture rather than science,though in many cases science has confirmedwhat culture has long known; not surprisingly, thesetwo different vocabularies, or ways of knowing, oftencome to the same conclusion (as when scientistsrecentlyconfirmed that the traditional practice ofeating tomatoes with olive oil is good for you, becausethe lycopenein the tomatoes is soluble in oil, making iteasier for your body to absorb). I have also avoided talkingmuch about nutrients, not because they aren’t important,but because focusing relentlessly on nutrientsobscures other, more important truths about food.

Foods are more than the sum of their nutrient parts,and those nutrients work together in ways that are stillonly dimly understood. It may be that the degree towhich a food is processed gives us a more importantkey to its healthfulness: Not only can processingremove nutrients and add toxic chemicals, but it makesfood more readily absorbable, which can be a problemfor our insulin and fat metabolism. Also, the plasticsin which processed foods are typically packaged canpresent a further risk to our health. This is why manyof the rules in this book are designed to help you avoidheavily processed foods—which I prefer to call “ediblefoodlike substances.”