Researchers of a new study published in the BMJ concluded there was no association between eating more saturated fat—the kind found in red meat, milk, butter, and egg yolks—and a higher risk of heart disease and other life-threatening conditions.
What study authors did report was that a higher intake of trans fat—industrially-processed oils commonly found in processed cakes, margarines, and many snack foods—came with a 34 percent increase in death for any reason, a 28 percent increase in death risk from heart disease, and a 21 percent increase in heart disease risk overall.
Reading Between the Headlines
Newsweek’s story opened with, “Dairy-lovers and carnivores, rejoice,” and London’s Times headline read, “Welcome back to butter on toast.”
The news headlines since the study was published yesterday make it sound like the study is one big endorsement for meat, butter, and the things many people find hard to give up. Not so.
The study’s lead author, Russell J. De Souza, ScD, RD, from McMaster University in Ontario, Canada, does not recommend that people increase their intake of saturated fats. He tells The Independent: “We aren’t advocating an increase of the allowance for saturated fats in dietary guidelines, as we don’t see evidence that higher limits would be specifically beneficial to health.”
What’s not making headlines is his very serious advice that “we should not ignore stronger and consistent evidence from better-designed studies that eating less saturated fat … reduces the chance of developing or dying from heart disease.”
Why Do These Findings Go Against Current Medical Advice?
No matter the headlines, most researchers and doctors aren’t jumping on board the butter bandwagon. This meta-analysis, which looked at 73 earlier observational studies of healthy adults, relied on food questionnaires. Randomized trials, which generally show better evidence of cause and effect, have consistently shown that saturated fat raises LDL cholesterol levels and increases risk of cardiovascular disease.
Dr. Dean Ornish, clinical professor of medicine at the University of California, San Francisco, responded to the study in a letter to the editor. He wrote:
“These data showed just the opposite: intake of saturated fats was significantly correlated with each of these measures … The article looked at data in two ways: most adjusted for covariates and least adjusted. In the abstract, only the most adjusted data were reported, yet the least unadjusted data showed a statistically significant relationship between intake of saturated fats and increased all-cause mortality, mortality from cardiovascular disease, prevalence of coronary heart disease, risk of stroke, and risk of type 2 diabetes.”
Dr. Ornish also pointed out that the study’s conclusions did not look at the relationship between saturated fat and the whole dietary pattern. He notes that the least adjusted data showed that “replacing dietary saturated fats with ‘good carbs’ such as fruits, vegetables, and whole grains, reduced the risk of cardiovascular disease.”
Dr. Robert Ostfeld, director of the Cardiac Wellness Program at Montefiore Medical Center, elaborates on why these study adjustments matter:
“One weakness of this study is overadjustment bias, or statistically adjusting for things we should not. Why is that a weakness? In a hypothetical analysis of firearm deaths, if we ‘adjust’ for bullets, meaning removing their impact on death, we may find that firearms are not associated with death at all, which is of course ludicrous. Here, the investigators adjusted for cholesterol, and that matters because saturated fat raises cholesterol. Hence, adjusting for cholesterol eliminated a reason saturated fat is bad. They took the ‘bullets’ out of saturated fat. Accordingly, that may make saturated fat look better when it really shouldn’t. And interestingly, when the authors did not overadjust, saturated fat was associated with more death and cardiovascular disease.”
It’s the Whole Diet That Matters
De Souza makes it clear that despite the study’s conclusions, he and the other study authors do not want people to deduce that they should eat more butter, meat, or saturated fat. In addition, he tells Newsweek, “People who reduce their intake of fat usually end up eating more sugar, white flour, and empty calories.” He goes on to say that “there’s really no one nutrient or food which is responsible for all heart disease or diabetes or death … the whole diet matters.”
Dr. Ostfeld concurs that good health is about more than just the absence or addition of one nutrient. In response to the study, he tells Forks Over Knives:
“Although this analysis is interesting, it is reductionist and I believe of limited value in the real world. When is the last time you ate a bowl of saturated fat? People eat food. Studies focusing on the health impact of differing amounts of saturated fat intake often fail to look at what the subjects are actually eating. Many foods that are low in saturated fat are still unhealthy. Therefore, what you eat instead of foods high in saturated fat is also critical. Many such study participants are giving up one unhealthy food (such as meat and dairy) for another (such as highly processed grains and no-fat dairy), making a ‘low fat’ diet look just as bad as a higher fat one. Not surprisingly, when you replace an unhealthy diet with an unhealthy diet, they both look about the same. Indeed, the authors of this very study state that if you replace saturated fat with plant-based foods, people do better. Perhaps that should be the headline.”