February 19, 2019
Is Butter Back?
Be Well

Is Butter Back?

by John Swartzberg, M.D.  

One of our most popular articles, based on traffic to our website, was about cheese and its potential health benefits, despite its high saturated fat content. Some of our readers have asked us, what about butter? Butter has seemed to be an exception to the pardon granted other dairy foods—until now.

In June 2016, a systematic review and meta-analysis in the online journal PLOS ONE gave butter a pass, too. It pooled data from nine large studies involving more than 600,000 people and found that a daily serving of butter (about one tablespoon) was associated with no effect on cardio­vascular risk, a small (4 percent) reduction in diabetes risk, and a tiny (1 percent) increase in all-cause mortality rate. The researchers noted that these findings relate to the average effects of butter across large populations, and that “the health effects of any food could be modi­fied by a person’s background diet, genetics, or risk factor profile.”

The researchers found no randomized clinical trials on butter’s effects on these endpoints, which would provide the strongest evi­dence. So they had to rely on observational studies, which merely show associations and are prone to an array of problems. For instance, such studies depend on food questionnaires, which can be inaccurate. And while researchers control statistically for many demographic, life­style, and dietary variables, unmeasured factors (called residual con­founders) may partly account for the results. I’m usually hesitant to draw conclusions from such observational studies, though they can, in fact, be valuable when put in the context of other types of research, notably lab studies and clinical trials.

In the case of this new butter analysis, I’m not convinced by its findings. Yes, as we’ve reported, the evolving science on saturated fat suggests that not all types and sources are bad for heart health—even if they do raise LDL (“bad”) cholesterol (see The End of the Debate? Fat Chance). Nutritional context is crucial, however. The benefits of most dairy foods, for instance, may derive largely from the calcium and other healthful compounds they contain, the fermentation process they undergo (like many cheeses), or their bacterial cultures (as in yogurt).

In contrast, butter is pretty much just milk fat. Even if it turns out not to be a dietary villain, it is hardly a “health food.” The authors of the analysis suggested that butter is not as unhealthy as added sugar or refined grains, such as white bread, but that margarines (without trans fats) and vegetable oils rich in unsaturated fats “appear to be healthier choices.”

That makes sense. Much research has linked foods high in unsatu­rated fat to lower LDL and reduced risk of heart disease. In July 2016, for example, a Harvard study in JAMA Internal Medicine concluded that replacing foods high in saturated fat with those rich in unsaturated (especially polyunsaturated) fat is associated with a significantly reduced mortality rate. This was also an observational study, but it fits in with a large constellation of research. That’s why I’ll continue to usu­ally opt for olive oil, not butter, on my whole-grain bread. But if you love butter, go ahead and enjoy it. In moderation, of course.