Why Our Diet Changed
Like most American women, Susan is the one in her family who usually shops for food, plans the meals, and prepares them. Because she is largely responsible for deciding on the foods that she and her family will eat and she wants everyone to be healthy, she tries to choose foods that she believes will foster good health. To help her do this, she reads the nutrition information and ingredient lists on the labels of processed or packaged foods. She pays particular attention to the amount of total and saturated fat and the number of calories per serving. And she’s also familiar with the national Dietary Guidelines and its “food pyramid,” which proclaims that fat—especially saturated fat—is supposed to be bad for us, while polyunsaturated fat is thought to be better.
Since every processed or packaged food that we buy has a label detailing its fat content, you would think that there must be no doubt that these fats have a strong impact on our health. Surely there must be strong scientific evidence that following these dietary recommendations will improve our health. We know, for example, that if you have high blood pressure, taking medication to lower it can help you live longer. We know this because medical studies have shown it to be true. We also know that having mammograms can reduce deaths from breast cancer in women over fifty because studies have shown that they do. If women didn’t believe that there was good evidence that it was beneficial, they certainly wouldn’t do it. So surely there must be many medical studies showing that following recommendations to change the fats in your diet will make you healthier.
But surprisingly, astoundingly, there aren’t. There are no credible studies that show that following the recommendations to reduce total and saturated fat while increasing polyunsaturated fat will make you healthier. In 1993, physicians began enrolling more than forty-eight thousand middle-aged American women in the most recent of many studies investigating the health benefits of changing fat in the diet in accordance with the goals long enshrined in our Dietary Guidelines. Half of the women were given intensive training and assistance to help them to decrease the total fat and saturated fat in their diets to levels even lower than those in our national goals. The other half were left alone to eat whatever they wanted.
The women with the intensive diet advice did remarkably well in changing their diets. They decreased the total fat, saturated fat, and cholesterol in their diets by a third while increasing the proportion of polyunsaturated fat. Their total fat and saturated fat intakes were well below the levels that the national goals and food labels aim for, just as the researchers had hoped they would be. They did even better than what the guidelines ask us to do. And the cholesterol in their blood did decrease by a small amount. Meanwhile, the women in the comparison group did not change their diets, and their cholesterol stayed the same.
After eight years had passed, the researchers looked at how many women in the two groups had suffered heart attacks or strokes or had died from either cause. They had expected that women who had changed their diets so dramatically would do much better than those who had not. But there was no difference in the number of heart attacks, strokes, or deaths between the women who had changed their diets and the women who had not changed. Changing dietary fat even more than our national goals call for made absolutely no difference to whether they had a heart attack or stroke or died from one.
But this is only one of many studies with the same negative results.
In the famous Framingham Heart Study, for example, which followed more than five thousand residents of a Massachusetts town for thirty years, there was no relationship between what people ate and whether they developed heart disease or died prematurely, and many other studies have also found no effect. One recent review analyzed twenty-one different studies and concluded that there was no evidence that saturated fat in the diet increases the risk of heart attacks or strokes. Another review found an astonishing lack of scientific evidence supporting any of the current recommendations in the Dietary Guidelines.
So how did we come to have dietary guidelines, national goals, food pyramids, and food labels telling us to change our diets and eat less of some fats and more of others if there were no studies showing that making these changes would make us healthier? It turns out that two men were largely responsible for bringing about the remarkable changes in the American diet: one who could not have been more eager to lead the charge, and one who would much rather not have been involved at all.
Ike’s Multibillion-Dollar Heart Attack
On a pleasant fall afternoon in September 1955, the thirty-fourth president of the United States, Dwight Eisenhower, then sixty-four, was playing a lackluster round of golf. His stomach was bothering him; could it have been that onion-laden hamburger he’d eaten for lunch? He tried to ignore his discomfort and kept playing. But a few hours after going to bed that evening, he awakened with a severe pain in his chest and asked his wife, Mamie, to bring him some milk of magnesia. After one look at him, Mamie insisted that they call his doctor, and tests soon showed that he had suffered a major heart attack caused by a clot blocking one of the coronary arteries that supplied blood to his heart.
Ike then made a fateful and courageous decision. Though he would be running for re-election the following year and his opponents were sure to make his health an issue, he decided to tell the American public exactly what had happened. The news that the country’s beloved president, the hero who had won the war against the Nazis, had suffered a serious heart attack sent a shock wave through the country. The stock market suffered its largest loss to date—shedding $14 billion in a single day -— and the American public instantly developed a voracious appetite for information about coronary arteries, atherosclerosis, and cholesterol.
Fortunately, the famous Boston heart specialist brought in to take charge of the president’s case, Dr. Paul Dudley White, was the perfect person to explain to the American public what had happened when he held a press conference three days later. The room was packed with reporters and television cameras. White, four years older than his patient, with his trim runner’s frame, rimless glasses, and graying hair, spoke with a reassuringly genteel accent. He said that the president’s heart attack was the result of one of his coronary arteries being blocked. White explained that the walls of these arteries tend to thicken as men reach middle age and become more likely to get blocked (due to what we now call atherosclerosis), and that this particular problem had become much more common in the past few decades. In fact, he said, this was now the most common serious illness affecting middle-aged American men, and they were having more heart attacks than men in any other country.
As to what causes this dangerous thickening of the walls of the arteries, White allowed that a man’s heredity, body build, occupation, stress and strain, diet, smoking, and alcohol use might be involved, but cautioned that “nobody has yet made an adequate study of these various underlying factors.” But there was one man who was already absolutely certain that he knew exactly what was causing the increase in heart disease in American men: Ancel Keys, a fifty-one-year-old professor of physiology at the University of Minnesota, was convinced that the only thing that really mattered was how much fat Americans were eating.
Ancel Keys Shouts, “Fat Is the Villain!”
It was three years earlier that Professor Keys found his answer to America’s heart disease epidemic, while sitting with his wife at an outdoor restaurant in sunny Naples, Italy, looking out at the sparkling blue waters of the Mediterranean.
He was there because a physician from Naples had told him that the men who lived there did not have heart attacks, a claim Keys very much doubted. After all, back in Minnesota, one in every seven businessmen was dying from a heart attack before age sixty-five. But Keys had found that his colleague’s claim was true: Heart attacks were quite rare in workingmen in Naples, and Italian men in general had only one-third as many fatal heart attacks as American men.
As he watched the Italian families around him digging enthusiastically into heaping plates of pasta covered with thick fragrant sauces of tomatoes and vegetables, he thought he understood why. Italians ate meat only once or twice a week and very little milk, cream, or butter. As a result, they were eating half as much fat as Americans and so, Keys thought, it must be this low-fat Italian diet that protected Italian men from heart disease. Keys paid little attention at the time to the many other ways the Italian diet was different from the American diet: fifty-five times more olive oil; twice as much bread, pasta, and fish; a third more fruit and vegetables; half as much sugar; and thirty-five times more wine. (Many years later, Keys would come to embrace some of the other elements of this “Mediterranean diet.”)
Even before his visit to Naples, Keys was already inclined to blame fat for the rise in heart disease, because he had found that putting Minnesota businessmen on a very low-fat diet lowered the cholesterol in their blood. And since the fatty deposits that block coronary arteries and cause heart attacks have a lot of cholesterol in them, it seemed to make sense that lowering cholesterol in the blood ought to help prevent heart disease. But there were two troubling problems. While many men with heart attacks had high cholesterol levels in their blood, most did not. And if you asked men to report on exactly what they ate, there was little connection between their diets and their blood cholesterol levels. Some men eat lots of fat and have low cholesterol; some eat very little fat and have high cholesterol. Even the amount of cholesterol present in the foods people eat, like eggs, has very little effect on the amount in their blood.
But as he sat there in sunny Naples, Keys decided that none of this mattered. It was not what any single person ate that was important -— it was what everyone ate, what all the people in a country ate. Italians must have less heart disease because they ate much less fat than Americans, so all he needed to do was to get Americans to eat less fat and the heart disease epidemic would melt away.
Soon after Keys returned to Minnesota, he wrote up his wonderful new idea that fat in the diet was the cause of the American heart disease epidemic. He showed that, in six different countries, the more fat there was in the diet, the more deaths there were from heart attacks. Unfortunately, he failed to mention that there were diet and heart disease figures for sixteen other countries that he had chosen to ignore. If he had included the figures from all of these countries, there would have been no relationship at all between dietary fat and deaths from heart disease, as other researchers soon pointed out. In fact, the three countries where men had the lowest death rates and highest life expectancy -— Norway, Sweden, and Denmark -— had just as much fat in their diets as the United States. But this and other inconvenient facts were consistently ignored by Keys and his followers. Today, we have data for 165 different countries, and these current worldwide statistics show that people in countries with more fat in the diet actually have fewer deaths from heart disease.
Keys thought that fat in the American diet also explained why heart disease in men had more than doubled from 1910 to 1950: because the percentage of calories from fat in our food supply had increased from 32 percent to 40 percent during that forty-year span. Fat calories in Italy were just 20 percent, and he was sure if we could just lower our percentage down to 30 percent, we would be much better off. And this is exactly how your “daily allowance” of fat on a food label is calculated today; it is 30 percent of the calories in a 2,000-calorie diet. Critics of Keys would point to an abundance of other evidence that showed that Americans had been eating a diet high in fat and animal fat long before the rise in heart disease. In fact, as later critics also pointed out, the small increase in fat in our diet that Keys blamed for the epidemic of heart disease was largely due to an increase in the same polyunsaturated vegetable oils Keys would later claim were beneficial.
There were other jarring facts. For example, neither Keys nor anyone else seemed to notice that there had been no epidemic of heart disease in women, even though they had been eating the same foods as men. In fact, deaths from heart disease in women had been slowly declining since the 1930s. Nor did anyone notice that something else had been increasing in American men at exactly the same time as heart disease: cigarette smoking, which, it turns out, triples the risk of a heart attack.
At the time of Eisenhower’s heart attack, Keys had already been promoting his ideas about fat and heart disease for three years, but no one had paid much attention. But now suddenly everyone was interested. Three weeks after Ike’s attack, Time magazine ran a cover story on heart disease in which Keys explained that the amount of fat in the American diet was the key to heart disease and that heredity, race, smoking, and obesity were much less important. A month later, Reader’s Digest featured a long article on Keys’s ideas about the evils of dietary fat: “Is This the No. 1 Villain in Heart Disease?”
Inspired by Keys’s ideas, General Mills became the first food company to claim it had a product that could reduce the chances of heart disease because it was low in fat: “Wheaties may actually help you live longer! Recent studies indicate that common heart ailments are more prevalent in groups living on high fat diets.” They all but quoted Keys: “We all need some fat. But 40 to 50 percent of all calories in the average American diet are fat! Far too much, caution many nutrition authorities.” Well, at least one authority. And so began Keys’s epic collaboration with the food makers to instruct the American public about the evils of certain kinds of fat and the virtues of their products.
Unfortunately for Keys -— and, as it turns out, for the rest of us -— just when the press and the public were getting on board with his antifat campaign, new evidence turned up that not all fats were bad. While saturated fat, like the fat from meat and dairy foods, could raise the level of cholesterol in the blood, polyunsaturated fat, found mostly in vegetable oils like corn and soybean oil, did not. In fact, large amounts of corn oil could actually lower cholesterol.
The only way we can get these polyunsaturated fats is from what we eat, because our bodies cannot make them. They come in two forms: omega-3 and omega-6. Because corn oil is quite high in the omega-6 fat called linoleic acid, this was mistakenly given credit for lowering cholesterol when it was actually something else in the corn oil (sitosterol) that was responsible. But the belief that omega-6 linoleic is beneficial has persisted.
Keys was very slow to admit that different kinds of fat have different effects -— even though he quickly confirmed this in his own laboratory -— because it distracted people from his “fat is the villain” message. But a big and insatiable genie was out of the bottle as food industry executives smelled a new source of profits. For them, the idea that polyunsaturated fat was healthier could not have come at a better time. They were already using more vegetable oil -— especially soybean oil -— high in polyunsaturated fat in their food products because it was cheaper and easier to use than animal fat. And they also knew that because women want to give their families healthy foods, pitching their advertising in terms of health benefits would be a good way to sell them.
The Polyunsaturated Explosion
Quickly responding to the new research suggesting that polyunsaturated fats might be better than saturated fats, the Corn Products Refining Company debuted Mazola Corn Oil, promoting it as “unsaturated” and “nutritionally unexcelled.” As the company’s vice president modestly explained: “We don’t want to appear to be medical men, but if Mazola can be used to alleviate nutritional malfunctions or improve anyone’s health then obviously we’re all for it -— and no one can hurt himself by eating Mazola.”
Despite the enthusiasm of the ad companies, most physicians remained skeptical about Keys’s ideas. Joining with Keys in a telethon to raise money for the American Heart Association, Eisenhower’s sainted cardiologist, Paul Dudley White, stunned his cohost by publically rejecting his diet-heart theory: “See here, I began my practice as a cardiologist in 1921 and I never saw an MI [heart attack] patient until 1928. Back in the MI-free days before 1920, the fats were butter and lard and I think that we would all benefit from the kind of diet that we had at a time when no one had ever heard the word corn oil.” White knew that vegetable oils had been increasing in the American diet during the time when heart disease was going up. In fact, the share of calories from polyunsaturated fat had doubled from 1910 to the 1950s, while saturated fat had only increased by one-fifth.
The physician president of the American Heart Association now decided it was time for his public service group to weigh in on diet and heart disease. He asked four other expert physicians to join him in reviewing the evidence and invited Keys to present his ideas. Much to Keys’s dismay, the panel’s published report poked holes in every part of his argument. The panelists rejected his view that Americans were eating more fat than they used to, pointing to plenty of evidence of high fat intakes in the past, just as Dr. White had. Also, just as Keys himself had found, they noted that what people eat is not strongly related to the level of their blood cholesterol and that the cholesterol level is not a very good predictor of heart disease risk.
Worst of all, they rejected Keys’s central argument that the number of heart disease deaths is strongly linked to the amount of fat in a country’s diet, pointing to the many countries with high-fat diets and low heart disease rates. They also noted that countries with fewer deaths from heart disease often have more deaths from other causes and shorter overall life spans, something that Keys also found in his own studies. Yet for the next thirty years, diet-heart enthusiasts constantly referred to Keys’s argument based on six or seven countries as the strongest and most convincing evidence for a link between diet and heart disease. They had to fall back on this, because there weren’t any studies showing that changing your diet lowers your risk of heart disease.
Join us for a discussion of Why Women Need Fat in BlogHer Book Club.
More from entertainment