Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating

First Chapter

Chapter One: Introduction

We eat to live.

It's a simple, obvious truth. We need food for the basics of everyday life -- to pump blood, move muscles, think thoughts.

But we can also eat to live well and live longer. By making the right choices, you will help yourself avoid some of the things we think of as the inevitable penalties of getting older. A healthy diet teamed up with regular exercise and no smoking can eliminate 80 percent of heart disease and 70 percent of some cancers. Making poor choices -- eating too much of the wrong kinds of food and too little of the right kinds, or too much food altogether -- increases your chances of developing cancer, heart disease, diabetes, digestive disorders, and aging-related loss of vision. An unhealthy diet during pregnancy can even cause some birth defects.

Separating what's good from what's bad can be a discouraging task. Each day you have to choose from an ever increasing number of foods and products, some good, most not so good. Maybe the time you have to prepare food, or even to eat, seems to shrink by the month. To make matters worse, you may feel overwhelmed by contradictory advice on what to eat. Your daily newspaper or TV newscast routinely serves up results from the latest nutrition studies. Magazines trumpet the hottest diets complete with heartfelt testimonials. One new diet or nutrition book hits the bookshelves every other day. Even supermarkets and fast-food restaurants offer advice, as do cereal boxes and a sea of Internet sites. This jumble of information quickly turns into nutritional white noise that many people tune out.

TURNING TO THE USDA PYRAMID IS A MISTAKE

For no-nonsense, rock-solid nutrition information, people often look to the Food Guide Pyramid developed by the U.S. Department of Agriculture (USDA). It is supposed to offer straight talk that rises above the jungle of misinformation and contradictory claims.

That's a shame, because the USDA Pyramid is wrong. It was built on shaky scientific ground back in 1992. Since then it has been steadily eroded by new research from all parts of the globe. Scores of large and small research projects have chipped away at the foundation (carbohydrates), the middle (meat and milk), and the apex (fats). The Dietary Guidelines for Americans, which are supposed to serve as the detailed blueprint for the USDA Pyramid, are a bit better. They are updated every five years and sometimes include ready-for-prime-time research. But the USDA Pyramid hasn't really changed in spite of important advances in what we know about nutrition and health.

At best, the USDA Pyramid offers wishy-washy, scientifically unfounded advice on an absolutely vital topic -- what to eat. At worst, the misinformation contributes to overweight, poor health, and unnecessary early deaths. In either case it stands as a missed opportunity to improve the health of millions of people.

REBUILDING THE FOOD PYRAMID

I wrote this book to show you where the USDA Pyramid is wrong and why it is wrong. I wanted to offer a new healthy eating guide based on the best scientific evidence, a guide that fixes the fundamental flaws of the USDA Pyramid and helps you make better choices about what you eat. I also wanted to give you the latest information on new discoveries that should have profound effects on our eating patterns.

The Healthy Eating Pyramid is just as simple as the USDA Food Guide Pyramid. You don't have to weigh your food or tally up fat grams. There are no complicated food exchange tables to follow. You needn't eat odd combinations of foods or religiously avoid a particular type of food. Instead, our pyramid aims to nudge you toward eating mostly familiar foods that have been shown to improve health and reduce the risk of chronic disease. It involves simple changes you can make one at a time. Because it's an eating strategy aimed at improving your health instead of a diet aimed solely at helping you shed pounds, and because the changes suggested in this book can make your meals and snacks tastier, it is something you can stick with for years.

The Healthy Eating Pyramid isn't a single cute idea dolled up in a catchy graphic. It is the distillation of evidence from many different lines of research. This shouldn't be an important point, but it is. Few of the diets used by millions of Americans today are built on this kind of solid evidence. That was certainly clear from the "Great Nutrition Debate" sponsored by the USDA in February 2000. It brought together several authors of best-selling diet books for a lively, but mostly evidence-free, food fight. The wildly different recommendations presented in that three-hour session -- eat lots of meat, don't eat any meat, eat lots of carbohydrates, don't eat any carbohydrates, cut your intake of fat to under 20 percent of calories, eat as much fat as you want, stay away from sugar, eat potatoes -- neatly captured the chaos that we get in place of sound, sensible, and solid advice on healthy eating. This jumble of contradictions prompted USDA undersecretary Shirley Watkins to say afterward, "We will stand behind the Pyramid." But the USDA Pyramid isn't much better than most of these unsubstantiated diets!

THE HOLES IN THE USDA PYRAMID

Some recommendations on diet and nutrition are misguided because they are based on inadequate or incomplete information. Not the USDA Pyramid. It is wrong because it ignores the evidence that has been carefully assembled over the past forty years. Here are the USDA Pyramid's main and most health-damaging faults:

• All fats are bad. There's no question that two types of fat -- saturated fat, the kind that's abundant in whole milk or red meat, and trans fats, which are found in many margarines and vegetable shortenings -- contribute to the artery-clogging process that leads to heart disease, stroke, and other problems. But the USDA Pyramid's recommendation to use fats "sparingly" ignores the fact that two other kinds of fat -- the monounsaturated and polyunsaturated fats found in olive oil and other vegetable oils, nuts, whole grains, other plant products, and fish -- are good for your heart.

• All "complex" carbohydrates are good. Carbohydrates form the base of the USDA Pyramid. It suggests six to eleven servings of bread, cereal, rice, and pasta a day. But as with fats, this advice is too simplistic and overlooks essential research showing that the types of carbohydrates you eat matters a lot.

Most dietary guidelines recommend limiting simple carbohydrates (sugars) and eating plenty of complex carbohydrates (starches). White bread, potatoes, pasta, and white rice all fit this description and are the main sources of carbohydrates in the American diet. While the terms simple and complex have a specific chemical meaning, they don't mean much inside your body. In fact, your digestive system turns white bread, a baked potato, or white rice into glucose and pumps this sugar into the bloodstream almost as fast as it delivers the sugar in a cocktail of pure glucose. Swift, high spikes in blood sugar are followed by similar surges in insulin. As all this insulin forces glucose into muscle and fat cells, blood sugar levels plummet, triggering the unmistakable signals of hunger. To make matters worse, these high levels of blood sugar and insulin surges are now implicated as part of the perilous pathway to heart disease and diabetes. The harmful effects of these rapidly digested carbohydrates are especially serious for people who are overweight.

The carbohydrates that should form the keystones of a healthy diet come from whole grains, like brown rice or oats, from foods made with whole grains, like whole-wheat pasta or bread, or from beans. Your body takes longer to digest these carbohydrate packages, especially when they are coarsely ground or intact. That means they have a slow, low, and steady effect on blood sugar and insulin levels, which protects against heart disease and diabetes. They make you feel full longer and so keep you from getting hungry right away. They also give you important fiber plus plenty of vitamins and minerals.

The central message in the USDA Pyramid is that you should feel good about eating carbohydrates, especially if you are eating them in place of fats. But if you eat too much of the wrong kinds of carbohydrates and too little of the good kinds of fats, you can set yourself up for the same problems you may be trying to solve.

• Protein is protein. The protein group occupies one of the upper chambers of the USDA Pyramid. You need this type of nutrient every day and can get it from a variety of sources. The USDA Pyramid serves up as equals red meat, poultry, fish, eggs, beans, and nuts. All are excellent sources of protein. But red meat is a poor protein package because of all the saturated fat and cholesterol that come along. Red meat may also give you too much iron in a form you absorb whether you need it or not. Chicken and turkey give you less saturated fat. The same is true for fish, which delivers some important unsaturated fats as well. As protein sources, beans and nuts have some advantages over animal sources. They give you fiber, vitamins, minerals, and healthy unsaturated fats. Like fruits and vegetables, they also give you a host of phytochemicals, an ever expanding collection of plant products that help protect you from a variety of chronic diseases.

• Dairy products are essential. The USDA Pyramid includes two to three servings of dairy products a day. It's a message that the hip "Got Milk?" and even hipper "milk mustache" ads (all sponsored by the dairy industry) hammer home to every possible demographic group. As a prime source of calcium, dairy products have been enlisted to fight the so-called calcium emergency that is threatening Americans' bones. Only there isn't a calcium emergency. Americans get more calcium than the residents of almost every other country except Holland and the Scandinavian countries. And despite plenty of urgent public service announcements, there's little evidence that getting high amounts of calcium prevents broken bones in old age. Further complicating the issue are some studies suggesting that drinking or eating a lot of dairy products may increase a woman's chances of developing ovarian cancer or a man's chances of developing prostate cancer.

If you need extra calcium, there are cheaper, easier, and healthier ways to get it than dairy products. Whole-milk dairy products are loaded with the kind of saturated fat that is most powerful at raising cholesterol levels. One percent and skim milk are clearly better choices. Spinach, broccoli, tofu, and calcium-fortified orange juice and breakfast cereals are good sources of calcium and have other advantages -- they are lower in unhealthy fat than most dairy products, and they give you many extra nutrients. Finally, dairy products are an expensive way to get calcium. Calcium supplements or calcium-based antacids cost pennies a day (and they are mostly calorie-free, to boot) compared with up to a dollar a day for two to three servings of dairy products.

• Eat your potatoes. According to the USDA, the average American eats 140 pounds of potatoes a year, making the spud the most popular vegetable in America. It is one of the few vegetables to be mentioned by name in the Dietary Guidelines -- except it shouldn't be classified as a vegetable. Potatoes are mostly starch -- easily digested starch at that -- and so should be part of the carbohydrate group. While more than two hundred studies have shown that people who eat plenty of fruits and vegetables decrease their chances of having heart attacks or strokes, of developing a variety of cancers, or of suffering from constipation or other digestive problems, the same body of evidence shows that potatoes don't contribute to this benefit.

Nutritionists and diet books alike often call potatoes a "perfect food." But while eating potatoes on a daily basis may be fine for lean people who exercise a lot or who do regular manual labor, for everyone else potatoes should be an occasional food consumed in modest amounts, not a daily vegetable. The venerable baked potato increases levels of blood sugar and insulin more quickly and to higher levels than an equal amount of calories from pure table sugar. French fries as they are usually sold do much the same thing, while also typically packing an unhealthy wallop of trans fats.

• No guidance on weight, exercise, alcohol, and vitamins. Like the Sphinx, the USDA Pyramid is silent on four things you need to know about -- the importance of not gaining weight, the necessity of daily exercise, the potential health benefits of a daily alcoholic drink, and what you can gain by taking a daily multivitamin.

HOW THE USDA PYRAMID GOT ITS SHAPE

In Rudyard Kipling's classic children's story, the satiable Elephant's Child got its long trunk in a terrific tug-of-war, with Crocodile clamped on to its nose and Bi-Coloured-Python-Rock-Snake wrapped around its legs. That's pretty much how the USDA Pyramid got its structure -- yanked this way and that by competing powerful interests, few of which had your health as a central goal.

The thing to keep in mind about the USDA Pyramid is that it comes from the Department of Agriculture, the agency responsible for promoting American agriculture, not from agencies established to monitor and protect our health, like the Department of Health and Human Services, or the National Institutes of Health, or the Institute of Medicine. And there's the root of the problem -- what's good for some agricultural interests isn't necessarily good for the people who eat their products. (This schizophrenic split isn't unique to the USDA. The Nuclear Regulatory Commission, for example, is charged with the often contradictory tasks of promoting nuclear power and regulating its use.)

Serving two masters is tricky business, especially when one of them includes persuasive and well-connected representatives of the formidable meat, dairy, and sugar industries. The end result of their tug-of-war is a set of positive, feel-good, all-inclusive recommendations that completely distort what could be the single most important tool for improving your health and the health of the nation.

THIS HEALTHY EATING PYRAMID IS BASED ON SCIENCE

You deserve more accurate, less biased, and more helpful information than that found in the USDA Pyramid. I have tried to collect exactly that in the Healthy Eating Pyramid. Without question, I have the advantage of starting with a lot more information than the USDA Pyramid builders had ten years ago. Equally important, I didn't have to negotiate with any special-interest groups when it came time to design this Pyramid.

The Healthy Eating Pyramid isn't set in stone. I don't have all the answers, nor can I predict what nutrition researchers will turn up in the decade ahead. But I can give you a solid sense of state-of-the-art healthy eating today and point out where things are heading. This isn't the only alternative to the USDA Food Guide Pyramid. The Asian, Latin, Mediterranean, and vegetarian pyramids promoted by Oldways Preservation and Exchange Trust are also good, evidence-based guides for healthy eating. But the Healthy Eating Pyramid takes advantage of even more extensive research and offers a broader guide that is not based on a specific culture.

About the only thing that the Healthy Eating Pyramid and the USDA Food Guide Pyramid share is their emphasis on vegetables and fruits. Other than that, they are different on almost every level. In the chapters that follow, I will lay out the evidence that shaped this blueprint for healthy eating and will also chart out extra information to help people with special nutritional needs get the most benefit from what they eat. These people include pregnant women, older people, and people with, or at high risk of, heart disease, diabetes, high cholesterol, high blood pressure, and some other chronic conditions.

For now, though, the following list of the seven healthiest changes you can make in your diet offers an overview that describes how the Healthy Eating Pyramid differs from the USDA Pyramid. Topping the list is controlling your weight.

• Watch your weight. When it comes to long-term health, keeping your weight from creeping up on you is more important than the exact ratio of fats to carbohydrates or the types and amounts of antioxidants in your food. The lower and more stable your weight, the lower your chances of having or dying from a heart attack, stroke, or other type of cardiovascular disease; of developing high blood pressure, high cholesterol, or diabetes; of being diagnosed with postmenopausal breast cancer, cancer of the endometrium, colon, or kidney; or of being afflicted with some other chronic condition. Yes, it is possible to be too thin, as in the case of anorexia nervosa, but otherwise very few American adults fall into this category.

• Eat fewer bad fats and more good fats. One of the most striking differences is the placement of healthy fats in the foundation of the Healthy Eating Pyramid instead of relegating all fats to the "Use Sparingly" spot at the top. The message here is almost as simple as the USDA's and far better for you: Fats from nuts, seeds, grains, fish, and liquid oils (including olive, canola, soybean, corn, sunflower, peanut, and other vegetable oils) are good for you, especially when you eat them in place of saturated and trans fat.

The all-fat-is-bad message has started a huge national experiment, with us as the guinea pigs. As people cut back on fat, they usually eat more carbohydrates. In America today, that means more highly refined or easily digested foods like sugar, white bread, white rice, and potatoes. This switch usually fails to yield the hoped-for weight loss or lower cholesterol levels. Instead it often leads to weight gain and potentially dangerous changes in blood fats -- lower high-density lipoprotein (HDL), the so-called good or protective cholesterol, and higher triglycerides (a major type of blood fat).

Substituting unsaturated fats for saturated fats, though, improves cholesterol levels across the board. It may also protect the heart against rhythm disturbances that can end in sudden death.

The bottom line is this: It is perfectly fine to get more than 30 percent of your daily calories from fats as long as most of those fats are unsaturated. The Healthy Eating Pyramid highlights the importance of keeping saturated and trans fats to a minimum by putting red meat, whole-milk dairy products, butter, and hydrogenated vegetable oils in the "Use Sparingly" section at the top.

• Eat fewer refined-grain carbohydrates and more whole-grain carbohydrates. The Healthy Eating Pyramid has two carbohydrate building blocks -- whole grains that are slowly digested as part of the foundation and highly refined, rapidly digested carbohydrates at the very top.

For almost twenty years our research team has been one of several groups studying the health effects of foods made from refined and intact grains. The result of this work is compelling. Eating lots of carbohydrates that are quickly digested and absorbed increases levels of blood sugar and insulin, raises levels of triglycerides, and lowers levels of HDL cholesterol. Over the long run, these changes lead to cardiovascular disease and diabetes. In contrast, eating whole-grain foods is clearly better for long-term good health and offers protection against diabetes, heart disease, cancer, and gastrointestinal problems such as diverticulosis and constipation. Other research around the world points to the same conclusions.

• Choose healthier sources of proteins. In the Healthy Eating Pyramid, red meat occupies the pointy tip to highlight the fact that something about red meat -- its particular combination of saturated fats or the potentially cancer-causing compounds that form when red meat is grilled or fried -- is connected to a variety of chronic diseases. In this pyramid, the best sources of protein are beans and nuts, along with fish, poultry, and eggs. It separates vegetable and animal protein sources and makes the latter optional for people who want to follow a vegetarian diet.

• Eat plenty of vegetables and fruits, but hold the potatoes. Vegetables and fruits are essential ingredients in almost every cuisine. If you let them play starring roles in your diet, they will reward you with many benefits besides great taste, terrific textures, and welcome variety. A diet rich in fruits and vegetables will lower your blood pressure, decrease your chances of having a heart attack or stroke, help protect you against a variety of cancers, guard against constipation and other gastrointestinal problems, and limit your chances of developing aging-related problems like cataracts and macular degeneration, the most common causes of vision loss among people over age sixty-five. I've plucked potatoes out of the vegetable category and put them in the "Use Sparingly" category because of their dramatic effect on levels of blood sugar and insulin.

• Use alcohol in moderation. When the first reports appeared linking moderate alcohol consumption with lower rates of heart disease, many scientists thought that some other habit shared by drinkers, not the drinking, accounted for the benefit. Today the evidence strongly points to alcohol itself. Based on the best estimates available, one drink a day for women and one or two a day for men cuts the chances of having a heart attack or dying from heart disease by about a third and also decreases the risk of having a clot-caused (ischemic) stroke.

Like many drugs, alcohol's effects depend on the dose. A little bit can be beneficial. A lot can eventually destroy the liver, lead to various cancers, boost blood pressure, trigger so-called bleeding (hemorrhagic) strokes, progressively weaken the heart muscle, scramble the brain, harm unborn children, and damage lives.

The clear and ever present dangers of alcohol and alcohol addiction make the recommendation of moderate drinking a political hot potato. While I acknowledge the problems with alcohol, I think it is important to point out its possible benefits for middle-aged and older people.

If you don't drink alcohol, you shouldn't feel compelled to start. You can get similar benefits by beginning to exercise (if you don't already) or boosting the intensity and duration of your physical activity, in addition to following the eating strategy we describe. But if you are an adult with no history of depression or alcoholism who is at high risk for heart disease, a daily alcoholic drink may help reduce that risk. This is especially true for people with type 2 diabetes or those with low HDL that just won't budge upward with diet and exercise. If you already drink alcohol, keep it moderate.

• Take a multivitamin for insurance. Several of the ingredients in a standard multivitamin -- especially vitamins B₆ and B₁₂, folic acid, and vitamin D -- are essential players in preventing heart disease, cancer, osteoporosis, and other chronic diseases. At about a nickel a day, a multivitamin is a cheap and effective genuine "life insurance" policy. It won't make up for the sins of an unhealthy diet, but it can fill in the nutritional holes that can plague even the most conscientious eaters. A daily multivitamin is especially important for people who have trouble absorbing vitamins from their food and for those who can't, or don't, get out in the sun every day. A daily multivitamin is also important for people who drink alcohol because it provides extra folic acid. Alcohol interferes with the metabolism of this key vitamin.

USDA PYRAMID AND DIETARY GUIDELINES FAIL THE HEALTH TEST

Throughout this book I will talk about "the evidence." I hope I won't sound like an old, scratched record, repeating that there is or is not enough evidence on the benefits or risks of this or that strategy. But the evidence is what matters. Without it, recommendations are little more than opinions and educated guesses, and they may or may not accomplish what they set out to do.

In the ten years since the USDA Pyramid was designed and built, it has never been updated to reflect the wealth of new information that's become available on diet and health. Nor has it ever been tested to see if it really works. Until now.

A few years ago, the USDA's Center for Nutrition Policy and Promotion devised a score sheet called the Healthy Eating Index "to measure how well American diets conform to recommended healthy eating patterns." This index assigns scores of 0 to 10 for each of ten dietary components. Five come from the USDA Pyramid (number of daily servings of grains, vegetables, fruits, meat, and dairy products), and five come from the Dietary Guidelines for Americans (total fat in the diet, percentage of calories from saturated fat, cholesterol intake, sodium intake, and variety of the diet). A score of 100 would mean perfect adherence to the USDA's recommendations, while a score of 0 would mean total disregard for them.

My colleagues and I used the government's Healthy Eating Index to test whether people who follow the recommendations laid out in the USDA Pyramid are healthier than those who don't follow these guidelines. They aren't. Among over 121,000 female nurses who are participating in a long-term study of diet you'll be hearing more about in later chapters, those with the highest scores on the Healthy Eating Index were no less likely to develop a major illness or die than those with the lowest scores over a twelve-year period. Women scoring high on the Healthy Eating Index were only slightly less likely to have a heart attack. The pattern was similar for more than 50,000 male health professionals participating in a separate long-term study.

These dismal results shouldn't come as a surprise since the USDA Pyramid ignores the extensive body of evidence linking certain eating patterns with long-term health. Instead they should be a warning that the current USDA Pyramid won't help you eat to live well or live longer.

To be fair, we are now in the process of testing the Healthy Eating Pyramid. Because each of its building blocks comes from the finest possible quarry -- solid evidence amassed by researchers from around the world -- it has already passed the most important tests. I'm confident that the findings from this research will show that it can help keep you healthy.

WHAT'S IN THIS BOOK

Between the covers of this book is the latest thinking about diet and health. To give you a quick and easy guide, I distilled as much information as possible into the Healthy Eating Pyramid. But I also wanted you to see the blueprint -- the scientific evidence -- on which it is based. This is detailed in chapters 3 through 11. Along the way, I describe cutting-edge research that may radically change healthy eating patterns, including new information on the benefits of n-3 fatty acids found in some oils and nuts; on lycopene, a possible cancer-fighting substance found in tomatoes; on the potential hazards of getting too much calcium; and on why it makes sense to take a daily multivitamin.

This book also helps you incorporate this information into your snacks and meals with practical tips on buying healthy foods and eating defensively and a section that offers more than fifty tested, tasty recipes.

This information isn't meant to take the place of advice you get from your physician, especially if you have a medical condition that requires a specific diet. Instead I encourage you to talk about your diet with your health care provider or share what you've learned from this book with her or him to make sure you are on the same wavelength. Unfortunately, the pressures of modern medicine and health care often make it difficult for clinicians to spend time talking about healthy food choices with their patients.

Copyright © 2001 by the President and Fellows of Harvard College