In mid-March lots of us started hoping we could, finally, toss caution to the wind and chow down on juicy steaks, buttery croissants, and crispy fried chicken. That’s because a study in the Annals of Internal Medicine reported that cutting back on saturated fat has little effect on our risk of having a heart attack. Suddenly saturated fat—a major player in heart disease—wasn’t the dietary demon we thought. The researchers also concluded there was no clear evidence to support another morsel of heart-healthy dietary advice: That unsaturated fats—in foods such as fish, nuts, and olive oil—were good for the heart.
The “saturated-fat-isn’t-so-bad” message reverberated around the world. In an op-ed article in The New York Times, for example, the food journalist Mark Bittman wrote that while more research is needed “the days of skinless chicken breasts and tubs of I Can’t Believe It’s Not Butter! may finally be drawing to a close.”
Well, not so fast. About a week after the study was released (and a day after the Bittman column) the researchers announced that their findings contained important errors, though they insisted that their original conclusions were still valid. But many researchers, nutritionists, and cardiologists—some of whom were dubious about the results to begin with—grew even more skeptical. “The result of the analysis was to throw the olive oil out with the bathwater,” said Walter Willett, M.D., Dr. P.H., M.P.H., chair of the department of nutrition at the Harvard School of Public Health. “And many people are likely to be harmed.”
What’s was wrong with the study
Our medical experts see several problems with the study. “It is a flawed study,” Marvin M. Lipman, M.D. chief medical adviser for Consumer Reports, said. “And a flawed study should not supplant a well-substantiated theory of the mechanism of coronary atherosclerosis. To take one finding and throw out many other studies isn’t warranted.”
One big criticism is with the design of the study. The researchers looked at 72 previously published studies and combined the results. That kind of research, called a meta-analysis, can be tricky. Findings can be influenced by the studies included, and important ones can be left out. That was the case with this analysis. “There were gross errors in the extraction of data from the original studies,” said Willett, principal investigator of the Nurses Health Study II. “Also, important studies were excluded and not acknowledged in the discussion.”
One such study he said, showed a “clear benefit” on the heart when people replaced saturated fat with polyunsaturated fat. Also, according to Willet: “The authors ignored the last decade of research showing that whether saturated fat is good, bad, or indifferent depends upon the source of the calories to which it is compared. If people replace saturated fat with carbohydrates, the impact on heart disease will be minimal.”
Another issue: Some studies used in the analysis were based on what people told an interviewer. “During dietary interviews, people make mistakes or even lie to please the questioner,’ Lipman said. So these studies can be unreliable.
Read about how to eat a heart-healthy diet and how to lower your cholesterol levels.
“Dietary research is some of the hardest to conduct,” said David S. Seres, M.D., a member of Consumer Reports medical advisory board and director of medical nutrition and associate professor of medicine
at Columbia University College of Physicians and Surgeons. “While this study supports my own bias that we are far from really knowing what to recommend, it is difficult to conclude from it that we should make any changes in the dietary guidelines.”
Stick to the guidelines
Those guidelines advise us to limit saturated fat because it raises LDL (bad) cholesterol, increasing our risk for heart disease. And because saturated fat is also found in dairy products such as whole or reduced fat milk and ice cream, butter, palm oil and coconut oil, and baked goods and fried foods, we need to watch our intake of those as well.
Heart disease is serious stuff. Nearly 27 million Americans have been diagnosed with it, reports the National Centers for Disease Control and Prevention, and nearly 598,000 Americans die from it each year, making it the leading cause of death in the U.S. What’s more, too much saturated fat has been linked to an increased risk of colorectal cancer and other cancers.
On the other hand, polyunsaturated and monounsaturated fats are good for us. “We need an array of fatty acids,” Maxine Siegel, R.D., manager of product usability and food at Consumers Union, said. “Different acids seem to have different physiological functions.”
Omega-6 polyunsaturated fats are found in vegetable oils, including soybean oil, corn oil, and safflower oil. Omega-3s, which may also be good for the heart, are found in fatty fish such as salmon, mackerel, herring, trout, some nuts, and seeds such as walnuts and sunflower. Monounsaturated fats, found in nuts, vegetable, canola, sunflower, and olive oils and avocadoes, are also heart healthy, lowering LDL and reducing the risk of heart disease and stroke. (Read more about the different kinds of fats.)
Our advisers say the new findings shouldn’t change current advice about what to eat and not eat to keep our hearts healthy. “The jury is still out,” Siegel said. “This one particular study doesn’t provide a whole new body of evidence.”
More research into how diet affects heart health is needed, Lipman said. “We should take these findings into account as we do more studies in the future,” he said. “But I don’t think we should change our advice to patients on the basis of one finding.”
What should you do?
When it comes to matters of the heart, better safe than sorry. The American Heart Association advises limiting saturated intake to less than seven percent of daily calories. Current Dietary Guidelines recommend getting less than 10 percent of daily calories from saturated fat. Depending on the guidelines, someone who eats about 2,000 calories a day should get fewer than 140 or 200 calories, respectively, from saturated fat. Siegel says to aim for somewhere within this range. Limit trans fats to less than one percent of total daily calories. And contrary to what the new analysis found, polyunsaturated fats should be an important part of your diet, as should monounsaturated fats.
Because all fat packs a lot calories—each gram of fat contains nine calories, compared with four calories in a gram of protein—your total daily fat intake shouldn’t exceed 25 to 35 percent of calories. That means, if you down 2,000 calories a day, no more than 500 to 700 should come from fat.
Since it can be time consuming to keep track of all those fats, Siegel recommends following the Mediterranean Diet. “It decreases your saturated fat and is low in trans fat while increasing your intake of the good monounsaturated and polyunsaturated fats,” she said.
The eating plan emphasizes fresh fruit and vegetables, whole grains, beans, nuts and healthy polyunsaturated and monounsaturated fats such as the ones found in olive oil and canola oil, and fish and seafood a few times per week. You can eat poultry, eggs, cheese, and yogurt in moderation and sweets and red meat no more than a few times a month. A large study in the New England Journal of Medicine in 2013 found that people at high risk for heart disease lowered their risk for heart attack, stroke, and death from heart disease by about 30 percent if they followed a Mediterranean-style diet supplemented with either nuts or extra virgin olive oil instead of a low-fat diet.
Now that’s a result worth savoring.
—Catherine Winters
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