But digging a little deeper, the story becomes clearer. Clearer, actually, than most nutritional issues. And that story is that sitting fat is bad.
For a long time this was the prevailing idea, but then there were doubts. Given the backlash to Mark Bittman’s 2014 New York Times column Butter is Back, which pinned the headline on a meta-analysis concluding that saturated fat consumption was unrelated to increased risk of heart disease.
Since then, there have been others. And the trials have spawned plenty of sat-fat contrarians.
Going into this, I believed we should limit our intake of saturated fat, because I believe these two things:
1. Saturated fats raise LDL (aka bad) cholesterol.
2. LDL cholesterol increases the risk of heart disease.
I spoke to a couple of experts who were on the same page: cardiologist Ethan Weiss, formerly of the University of California at San Francisco and now an entrepreneur-in-residence at Third Rock Ventures, a biotech venture capital firm; and Kevin Klatt, a registered dietitian and researcher at the University of California at Berkeley. But I also wanted to talk to the smartest and most knowledgeable person I could find that he didn’t agree with me. Ronald Krauss is a professor at UC-San Francisco and co-author of a 2020 paper challenging the Department of Agriculture’s dietary guidelines recommendation that it limits saturated fat to 10 percent of calories. The recommendation to limit dietary saturated fatty acid (SFA) intake has persisted despite growing evidence to the contrary, the paper said.
The conversation with Krauss didn’t quite go as planned, as we started with one area of complete agreement: You can’t figure out saturated fat from observational research.
Much of the research that exempts saturated fat (including relevant portions of the study Bittman cites) comes from researchers following large groups of people, asking what they eat and seeing what diseases they get. I’ll spare you my rant about what a crappy tool I think this is, and just say that I think inaccurate data and a billion confounding factors preclude it from solving the saturated fat problem or looking for any causal link between food and health where the the effect is small.
Take those studies off the table and you’re left with clinical trials. Many of them.
Let’s take the connection between body fat and LDL first.
At least two things may affect whether and to what extent saturated fat raises LDL. One is the type of saturated fat and the other is the type of food it is contained in.
Four of the saturated fats we commonly eat (they have names, but are often referred to by the number of carbon atoms they contain) are C12 (lauric acid), C14 (myristic acid), C16 (palmitic acid), and C18 (stearic acid). According to Krauss and Klatt, C14 and C16 (which together are the majority of saturated fat in meat and dairy products) reliably raise LDL. C12 (the main fat in coconut oil) and C18 (which our bodies break down easily into a monounsaturated fat) are slightly different.
Food is also important. Even if two foods contain the same saturated fat, the effect on cholesterol can be different. There is evidence that some types of dairy products and yogurt, for example, don’t raise LDL as much as other foods high in saturated fat and can sometimes even lower it. No one is quite sure why (Krauss points out that there may be other properties of foods that have compensatory effects), but differences have been seen across a wide range of trials.
All saturated fats are not created equal. All foods that contain sat fat are not created equal. At the end of the day, however, I think it’s entirely tenable to say that saturated fat raises LDL cholesterol, even though some saturated fat foods like coconut oil and some dairy products, for example, don’t sound so bad.
But there’s only downside, of course, if raising LDL actually increases your risk of heart disease, and everyone I’ve talked to agrees that it does. Weiss calls it a borderline fact and Krauss is unequivocal: LDL is causal in cardiovascular disease. And there is ample evidence to support this; when lowering LDL reduces your risk of heart disease, that’s pretty telling. A 2016 meta-analysis found that reduced LDL levels were associated with lower rates of major coronary events. As did another one in 2020. So did a 2012 Mendelian randomization analysis. I could go on.
Again, though, there are some nuances. Weiss explains that some in the cardiology field (including Krauss) emphasize different types of LDL (small and dense, which can be more harmful than large and fluffy ones), and others focus on apoB, a protein that coats LDL particles and may be a better indicator of disease risk. While acknowledging these problems, he calls them a distraction. LDL cholesterol is still a good if not the best overall indicator of risk. It is easy and cheap to evaluate and is a good proxy for other measures that may be somewhat more accurate.
I asked Klatt and Weiss not just about fat and cholesterol but the extent of the consensus, and they both said it’s broad. Klatt called science super solid, something we don’t hear about nutrition all that often. To be clear, that doesn’t mean there aren’t processes that show something different; it’s just that the vast preponderance of the evidence points in the same direction.
Which brings us back to Krauss, who, as my chosen representative of Team Sat Fat, was a huge disappointment because he doesn’t dispute any of this. His objection to the recommendation to limit saturated fat isn’t because he thinks things are beneficial: I’ve never said there’s anything good about saturated fat. There’s no reason we need it in our diet. And, when he sees patients at high risk for heart disease, he tells them to limit it.
But, she says, if you’re trying to counsel someone who needs to reduce their risk of heart disease, it should involve limiting foods that are high in saturated fat. It’s not the same as population guidelines. Krauss gave me several reasons why he opposes the limit: not everyone has to reduce risk, the 10% limit is arbitrary, and he believes guidelines should focus on foods rather than nutrients, particularly since the food that contains saturated fat is important.
Reasonable people may disagree on a specific recommendation. Because the argument about the harm of saturated fat is so strong, I’m all for keeping it, though I generally agree that recommending foods or dietary patterns is better than focusing on specific nutrients.
However, I don’t think reasonable people can disagree much about saturated fat itself. Much of it, in most foods it figures in, raises LDL cholesterol, which increases your risk of heart disease.
That should fix it, don’t you think?
#Dont #backlash #Saturated #fats #bad