Headlines like “Butter is Back!” are alluring, but they’re also misleading. Here’s what Harvard researchers have to say about their misunderstood study.
What’s healthy in the news seems to come in cycles, doesn’t it? One month, low fat diets are healthy and the next it’s all about eating high protein, low carb, and high fat. The thing about these cycles is that many of the studies they’re based on are poorly designed, misunderstood, or industry-funded. There’s a great episode of On the Media about this that’s worth a listen.
The cycle of what’s healthy reminds me of a bit from one of my favorite movies: Woody Allen’s Sleeper. You can watch the scene in the video at the top of the page.
What’s healthy in the news isn’t always what’s actually healthy, though, and a story making the rounds right now with headlines like “Butter is Back” is a great example of this “healthy in the news” phenomenon in action. We want these stories to be true, right? Butter tastes good.
Like the On the Media folks warn: “If it sounds too good to be true, it probably is.” And the truth is that saturated fats increase our risk of health problems like heart disease and type 2 diabetes. Just ask the American Heart Association and the American Diabetes Association.
With that “Butter is Back” story, the truth is a lot more complex than what you probably saw reported. You can read the Harvard School for Public Health’s press release clarifying what the study really means below.
Butter is not back: Limiting saturated fat still best for heart health
For immediate release: September 28, 2015
Boston, MA ─ People who replace saturated fat (mainly found in meats and dairy foods) in their diets with refined carbohydrates do not lower their risk of heart disease, according to a new study led by researchers at Harvard T.H. Chan School of Public Health. On the other hand, those who replace saturated fats with unsaturated fats (found in vegetable oils and nuts) or whole grains lower their heart disease risk.
Many people fall back on carbs, especially refined carbs like white bread, when they reduce saturated fat in their diets, said senior author Frank Hu, professor of nutrition and epidemiology. This may in part explain findings from a controversial 2014 paper that called into question recommendations for limiting saturated fat for heart health, and led to headlines promoting the return of butter.
“Our research does not exonerate saturated fat,” said Hu. “In terms of heart disease risk, saturated fat and refined carbohydrates appear to be similarly unhealthful.”
The study appears online September 28, 2015 in the Journal of the American College of Cardiology.
This is the first prospective analysis to directly compare saturated fat with other types of fats and different types of carbohydrates in relation to heart disease risk.
Hu and colleagues looked at diet and health information from participants in two long-running observation studies, the Nurses’ Health Study (84,628 women) and the Health Professionals Follow-up Study (42,908 men), who were free of diabetes, cardiovascular disease, and cancer at baseline. Diet was assessed by food frequency questionnaires every four years. During follow-up, the researchers documented 7,667 cases of coronary heart disease (CHD).
They estimated that replacing 5% of energy intake from saturated fats with equivalent energy intake from either polyunsaturated fats, monounsaturated fats, or carbohydrates from whole grains was associated with 25%, 15%, and 9% lower risk of CHD, respectively. On the other hand, swapping 5% of saturated fat calories for the same amount of refined carbohydrates and sugars did not change CHD risk.
“In other words, refined carbs and sugars don’t lower CHD risk any more than saturated fats lower CHD risk (which they don’t),” said Adela Hruby, co-first author along with Yanping Li, both researchers in the Department of Nutrition. “People who choose refined carbs and sugars instead of saturated fat, thinking they’re making a healthier choice, are not doing themselves any favors in terms of heart health.”
The study’s analyses took into account cardiovascular risk factors such as age, body mass index, smoking, and physical activity.
“Our findings suggest that the low-fat, high-carb trends of the 1980s and 1990s are not effective in reducing risk of CHD,” said Li. “Dietary recommendations to reduce saturated fats should specify their replacement with unsaturated fats or with healthy carbohydrates, such as whole grains.”
The study cohorts were supported by grants of UM1 CA186107, R01 HL034594, R01 HL35464, R01 HL60712 and UM1 CA167552 from the National Institutes of Health.
“Saturated fat as compared to unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease: A prospective cohort study,” Yanping Li, Adela Hruby, Adam M. Bernstein, Sylvia H. Ley, Dong D. Wang, Stephanie E. Chiuve, Laura Sampson, Kathryn M. Rexrode, Eric B. Rimm, Walter C. Willett, Frank B. Hu, Journal of the American College of Cardiology, online September 28, 2015, doi: 10.1016/j.jacc.2015.07.055
Butter image via Shutterstock