Are Saturated Fats Good or Bad?

Butter is high in saturated fats. Dorling Kindersley/Getty Images

It's something almost everyone who is interested in nutrition knowsSaturated fats are bad for us. They clog our arteries and cause heart attacks.

It wasn't until recently, however, that many people stopped to ask if saturated fats were truly unhealthy. Many of the other "facts" about nutrition we've thought were true since the 1960s or so have been disproven. In fact, the Dietary Guidelines for Americans, on which the famous food pyramids and food plates have been built, have been changing in recent years. They have stopped emphasizing the importance of eating a low-fat diet. They now advise limiting sugar. They stopped the long-time idea that cholesterol in the diet is bad. But they still advise serious restrictions on saturated fats.

How Much Saturated Fat Is Advised?

The American Heart Association advises that no more than 5 to 6 percent of calories come from saturated fats, which is about 12 grams of saturated fat for the average person eating 2,000 calories per day. The 2015 Dietary Guidelines for Americans recommends limiting saturated fat to 10 percent of calories, which is about 22 grams of saturated fat.

Did You Know that a Tablespoon of Olive Oil Contains 2 Grams of Saturated Fat?

We think of saturated fats as mainly being in fatty meats, full-fat dairy products, and coconut oil, but all fats are a mixture of different fats, and they usually include some saturated fats. This is the main reason why it is quite difficult to eat a diet as low in saturated dietary fat as the American Heart Association recommends. It is also very difficult to get all the essential nutrients that are recommended on a daily basis on a diet that is very low in saturated fat.

So, What's the Verdict?

Although eating too much saturated fat could be bad for some people, or perhaps in some contexts (such as what else is in the diet) the evidence for it being bad all the time and for everyone isn't holding up very well.

How Did We Come to Believe That Saturated Fats Are Bad?

It was the result of a fight among scientists in the middle part of the 20th century. There never was a whole lot of solid evidence that saturated fat causes heart disease, and most of the evidence presented had glaring mistakes. For example, in one well-known experiment, the saturated fat group had a much higher number of heavy smokers in it.

What studies showed was that when people replaced saturated fats with liquid oils, such as corn oil, their blood cholesterol went down. Everyone assumed this would mean that those people would be less prone to heart disease. (In general, they weren't, but more on that later.)

Nevertheless, there were both advocates for and against the so-called Diet Heart Hypothesis, and the saturated fat side won. If you are interested in the history of the scientific food fight about heart disease (and more this topic in general) I recommend these three books:

  • Death By Food Pyramid (2014) by Denise Minger  
  • Good Calories, Bad Calories (2007) by Gary Taubes 
  • The Big Fat Surprise (2014) by Nina Teicholz  

What Has Happened Since Then?

A lot of experiments and observational research have been done in the 50 plus years since those scientists won the argument. So, you might think that if it was true that saturated fats make people have heart attacks or strokes that it would be getting clearer and clearer as the years went by. By now it should be 100 percent solid, right? Well, no, it's not. 

Christopher Ramsden: A Scientific Sherlock Holmes

Dr. Christopher Ramsden of the National Institutes of Health (NIH) has taken a different approach to the situation. Instead of leading yet another study, he has dug down into the data of older, high-quality studies that may not have gotten the notice they deserved. The most recent result was published in the British Medical Journal in April of 2016.

In this work, Ramsden went back to the Minnesota Coronary Survey, which followed over 9,000 people for four and a half years. These people were institutionalized, so their diets could be carefully controlled for the experiment. As is common in these studies, one group was given a normal diet, and in the other group oils high in polyunsaturated fats (mostly omega-6 fats) replaced saturated fats. Since only one publication had come out of this large study, Ramsden was interested in what other information could be obtained.

It turns out that among those who died during the course of the study, those over 65 were more likely to die if they were in the low-saturated-fat group!

Also, Ramsden found that there were autopsy reports available for about 30 percent of the people who had died during the study. He found that of the people who had autopsies, 22 percent of those who had eaten a normal diet died of a heart attack, while 41 percent of those in the low-saturated-fat group did.

What does this mean? It doesn't look good for "Team Saturated Fat is Bad," but we don't really know. As Ramsden stated in his report, "Given the limitations of current evidence, the best approach might be one of humility, highlighting limitations of current knowledge and setting a high bar for advising intakes beyond what can be provided by natural diets."

We might be tempted to assume that Dr. Ramsden's results were a rare occurrence—that is, we might if he hadn't done a similar analysis of unpublished data he obtained from the Sydney Heart Study published in 2013. The results were similar.

Does This Mean That Saturated Fat is Good?

Some of the results I've mentioned might make us think that saturated fats in our diet are not only "not bad," they are actually "good." Like Christopher Ramsden, I would counsel humility on this point. We just do not know at this time.

However, here are some intriguing thoughts and possibilities:

  • We often say "saturated fat" as if it's only one thing. There are actually lots of types of saturated fats, many of which are known to be used in different ways by the body. (For example, medium-chain triglycerides)
  • Saturated fats are more stable, and less prone to oxidation than other fats. It could be that some of the negative results found from adding polyunsaturated fats to the diet come from the fact that they are more easily oxidized, and this definitely would have negative effects on the body.
  • The oils used to provide polyunsaturates are mainly full of omega-6 fats, which could have inflammatory effects in the body.
  • A group of scientists in the Netherlands analyzed some of the data on saturated fats and hypothesized that saturated fats could be mostly neutral, but could have more negative effects under the condition of a high-carb diet, or a diet high in processed foods. Another idea that they and others have proposed is that people with metabolic syndrome or chronic inflammation are more likely to react negatively to saturated fats.

Obviously, we still have much to learn about this subject. However, the way I read the current evidence, people can stop assuming that the next burger they eat will clog their arteries!

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