New research has weakened the perceived link between saturated fat and heart disease. Today, many experts agree that refined carbs pose a much greater danger.
Is it possible — even imaginable — that nearly everyone has been wrong about saturated fat and its connection to heart disease? Brace yourself. Based on a wave of new research, all the dietary admonitions about saturated fat could end up being little more than a huge mistake.
“The question is whether saturated fat is harmful or is just a bystander,” says Ronald M. Krauss, MD, a lipid specialist and the director of atherosclerosis research at the Children’s Hospital Oakland Research Institute. “Saturated fat may have an effect on cardiovascular disease (CVD) risk, but the effect is so small that we just can’t detect it. We shouldn’t be demonizing saturated fat.”
Krauss can back up his opinion with hard science. He and his colleagues recently analyzed 21 published studies involving almost 350,000 people who were tracked from five to 23 years. Their conclusion: People who consumed the most saturated fat did not have a higher risk of heart disease, stroke or any other form of CVD. They published their findings last year in the American Journal of Clinical Nutrition.
Krauss is by no means the first doctor to question the role of saturated fat in CVD. But, if he and other critics are right, it raises a couple of important questions: How could anti-saturated-fat advocates make such a huge miscalculation? And do we now have a license to eat saturated fat with abandon?
The answers aren’t as simple or straightforward as you might think.
There’s no denying that scores of studies over many years have shown a link between saturated fat and CVD risk. Krauss believes, however, that many of the saturated-fat-is-bad studies have not accounted for diets that included a lot of sugars, refined carbs and trans fats, along with saturated fats.
“It doesn’t make sense to focus on just one feature of the diet, such as saturated fat, while ignoring the health effects of the overall diet,” he says.
Origins of a Theory
The late Ancel Keys, PhD, a researcher at the University of Minnesota, first linked saturated fat and cholesterol with the risk of CVD in the 1950s.
Keys was hailed as a pioneer in the area of nutrition and health at the time; in January 1961, he made the cover of Time. Less than 20 years later, Congress was recommending that Americans ditch saturated fats in favor of more carbs, and soon food companies were hawking low-fat everything.
Keys’s research has come under increasing criticism in recent years. Gary Taubes, author of Why We Get Fat and What to Do About It (Knopf, 2011), notes that Keys focused on the eating habits linking saturated fat to CVD in seven nations, “in which he could pretty much draw a straight line between saturated fat and CVD risk.”
According to Taubes, Keys ignored contradictory data from other nations, including France, where people ate a lot of fat but had a low incidence of CVD (the so-called French paradox), which would have led Keys to draw entirely different conclusions.
“More than 20 studies have shown that people who have heart attacks don’t eat more saturated fat than healthy people,” says Swedish researcher Uffe Ravnskov, MD, PhD.
Ravnskov, who has written several books on cholesterol, has been skeptical of the saturated fat–cholesterol theory of heart disease since the 1960s. “Eight studies have shown that people with stroke have eaten less saturated fat than healthy people,” he says. “And no dietary study has succeeded in lowering heart disease deaths by reducing intake of saturated fat.”
Enter Refined Carbs
Americans largely embraced the anti-saturated-fat gospel, substantially cutting their consumption from about 13.5 percent of total calories in the early 1970s to about 11 percent of calories by 2000. In 2006, the American Heart Association recommended that people cut their saturated fat even more — down to 7 percent of total calories, which is half of what people were eating 40 years ago. But there have been unforeseen consequences, Krauss notes. “If you cut down on saturated fat, what do you replace it with?”
Food manufacturers responded by creating thousands of products in which saturated fat and cholesterol were replaced with refined carbohydrates, sugars and trans fats. And therein lies the problem. Not only do trans fats drive bodywide inflammation, but foods rich in refined carbohydrates and sugars trigger sharp increases in blood-sugar and insulin levels, which then set the stage for weight and blood-sugar problems — the leading risk factors for type 2 diabetes and CVD. “Replacing saturated fat with refined carbohydrates and sugars does not decrease CVD risk,” says Krauss. “More and more, the evidence shows that eating more refined carbs and sugars increases CVD risk.”
The late Robert C. Atkins, MD, sounded the alarm about the increase in carb and sugar consumption in the 1980s, when he noticed a dramatic rise in obesity and type 2 diabetes. But his solution, a diet rich in saturated fats, was roundly criticized — mostly because people believed that Atkins advised avoiding all carbs, including vegetables, when, in reality, he meant refined carbs. It took years of research before his approach was eventually vindicated.
This may sound like heresy, but the science behind it is solid. Sabina Sieri, PhD, of Italy’s National Cancer Institute, for example, tracked almost 48,000 people over eight years and found that women who ate more refined carbs and sugars had a significantly greater risk of coronary heart disease than those with a lower refined-carb intake.
The Cholesterol Question
For several decades, medical and nutritional advice boiled down to this: Too much dietary saturated fat leads to higher levels of blood cholesterol and an increase in CVD risk. But several studies have shown that total blood cholesterol is not a reliable indicator of CVD risk, says Ron Hunninghake, MD, chief medical officer of the Riordan Clinic in Wichita, Kan., the largest nonprofit nutritional medical center in the United States. “That’s because half of the people who suffer a heart attack have normal cholesterol levels.”
To find a way to make sense of the relationship between blood cholesterol levels and CVD, researchers began looking at cholesterol fractions, such as low-density lipoprotein (LDL) and high-density lipoprotein (HDL), to get a better handle on CVD risk. These LDL particles happen to be one of Krauss’s primary areas of expertise, and his findings have challenged conventional thinking about the role of saturated fat and cholesterol in CVD.
Although LDL is widely regarded as the “bad” cholesterol, Krauss argues that it has a good side: While “pattern B” LDL consists of small, dense particles that are more likely to infiltrate blood-vessel walls and set the stage for blockages, high blood levels of “pattern A” LDL, which consists of large, fluffy particles, are associated with a lower risk of CVD.
It’s true that saturated fat does increase LDL levels, Krauss explains — but not in the way most people would expect. “We’ve shown in our own research that in the great majority of individuals, this increase in LDL reflects an increase in pattern A LDL.” That’s the good form of LDL. Saturated fat also boosts levels of the “good” HDL form of cholesterol.
Diets high in refined carbs, on the other hand, boost pattern B LDL and lower HDL cholesterol — thereby increasing the risk of CVD. “Little will be gained if saturated fat is simply replaced by carbohydrates, especially if these are mainly refined starches and sugar,” says Walter Willett, MD, DrPH, who heads the nutrition department at the Harvard School of Public Health.
Research by Marianne U. Jakobsen, PhD, of Aarhus University Hospital in Denmark, supports this argument. In a study of more than 53,000 men and women over 12 years, Jakobsen found that people were more likely to suffer a heart attack if they cut back on saturated fat, but then replaced it with a couple hundred more calories a day from high-glycemic foods, such as white breads, muffins, potatoes and desserts. But, if the people in the study replaced saturated fat with low-glycemic foods like vegetables, fruits and whole grains, they were less likely to have a heart attack.
The key, it seems, is not limiting saturated-fat intake, but avoiding insulin-provoking foods such as refined carbs and sugars — basically what Atkins had argued. “Atkins wasn’t right about everything, but he was right about insulin,” says Taubes. “He was probably more right than anyone else at the time.”
Eat Like Your Ancestors
Krauss’s research and dietary recommendations are relatively consistent with what’s known as the Paleolithic diet — that is, ancient eating habits that some scientists consider the ideal diet.
Loren Cordain, PhD, a professor in the department of health and exercise science at Colorado State University in Fort Collins, says that ancient peoples typically ate a diet rich in lean protein, fish and vegetables, with carbohydrates coming largely from root vegetables. Even though the meats contained saturated fat and cholesterol, Paleolithic diets were devoid of any kind of processed carbohydrate and sugar, with the occasional exception of honey.
“Given our ancestral diet, meal plans fairly high in quality proteins and low in processed carbohydrates would seem to be what most people are best suited to,” says Cordain. “Our genes are virtually identical to those in people living 20,000 years ago, and we evolved eating lean proteins and vegetables. Eating a lot of processed grains and sugars is a total mismatch for our genetic heritage.”
That doesn’t mean you have to give up carbs altogether, or load up on saturated fats, to avoid a heart attack. As with most dietary issues, it’s a matter of finding a good balance. (See the sidebar, “A Bountiful Balance,” for some simple tips on healthful eating.)
Hunninghake generally concurs with this approach, but suggests that people tailor their carb intake to their weight, blood sugar and activity level. “If they’re good on all three counts, they can probably consume a little more in the way of carbs,” he says. “But if they’re overweight, have high blood sugar and are couch potatoes, they should be getting their carbs from high-fiber vegetables, not grains.”
Many people may find all this a bit disconcerting and confusing. And Krauss and Hunninghake’s advice does fly in the face of largely vegetarian diets recommended by some other physicians, including cardiovascular bigwigs like Dean Ornish, MD. In clinical trials, Ornish has had success reducing cardiovascular disease in subjects who adhere to a whole-foods, plant-based diet very low in saturated fat. But that doesn’t necessarily prove that avoiding saturated fat is a heart-healthy strategy.
“While these diets did reduce CVD, it’s not clear that reducing the saturated fat was what did it — most likely it was eating less junk food and more veggies,” says Hunninghake. “Nutrition isn’t religion. It should be based on science. And the evidence for scientific assumptions can and does change from time to time.”