Preventive Medicine Column
Dr. David L. Katz
In my view, an increasingly strident debate about the health effects of saturated fat ranks among illusory nutrition controversies. The answers being espoused with ever greater passion and conviction are in response to the wrong question. The question being asked, it seems, is: is saturated fat truly harmful? The right question is: is all saturated fat created equal?
It is not. Saturated fat is not a compound, but a class of compounds. And we have long had strong indications that the class is home to both baby, and bath water.
Stearic acid is a long saturated fat molecule, and seems to exert no harmful effects. It is one of the fats found in meat, and the predominant saturated fat found in dark chocolate. The 2010 Dietary Guidelines Advisory Committee very reasonably recommended that when we speak of restricting saturated fat intake, stearic acid need not be included.
There is less, but increasing evidence that lauric acid- a short saturated fat molecule- may also be innocuous. It is the kind of saturated fat that predominates in coconut oil- and the reason why the jury is still out on the health effects of its use.
I consider the evidence strong that palmitic and myristic acids, two of the commonly consumed saturated fats, are, indeed, potentially harmful, contributing to inflammation, elevated lipids, atherogenesis, and vascular disease.
Note that even the exonerated saturated fat molecules appear to be harmless, rather than health-promoting per se. While it is true that a 2010 meta-analysis in the American Journal of Clinical Nutrition found no clear link between saturated fat in the diet and the risk of cardiovascular disease, it is also true that a 2010 meta-analysis in PloS Med concluded that replacing dietary saturated fat with unsaturated fat reduces the risk of heart disease! Nowhere in any of the evolving science is there a basis for the active promotion of saturated fat intake, which I am nonetheless hearing from certain quarters.
We have innumerable studies showing that saturated fats – notably palmitic and myristic acids which are found in dairy, meat, and many processed foods- can increase blood lipids and contribute to inflammation. While it’s true that such fats may tend to raise HDL along with LDL, recent research raises questions about whether that’s the benefit it appeared to be. And while it’s also true that an excess of omega-6 polyunsaturated fats, and/or a deficiency of omega-3s can contribute to inflammation, that doesn’t mean that saturated fats don’t! It also seems likely that harms of saturated fat are very much compounded by the company they keep. Processed meat, for instance, is more clearly linked to bad health outcomes than just plain beef or pork.
Second, all oils are a mix of fatty acid types. While we think of olive oil as monounsaturated, it in fact contains monounsaturated, polyunsaturated, and saturated fatty acids. Oleic acid, a monounsaturate, merely predominates. Since oils and foods contain a mix of fatty acids, we are almost never making pure comparisons of one type of fat to another, and for this reason, we might expect to see some overlap in health effects. In the real world, ‘all good’ vs. ‘all bad’ is reliably more about salesmanship than data.
Third, and most important, we have very compelling evidence regarding the kinds of foods and diets that are associated with reduced risk of premature death and chronic disease- and they are not diets high in saturated fat! The Lyon Diet Heart Study compared a Mediterranean-style diet rich in monounsaturated fats to a “typical French” diet much richer in saturated fat among people who had had a first heart attack. The rate of 2nd heart attack was 70% lower among those on the Mediterranean diet! So much for the French paradox. The same results have been achieved on a plant-based diet, very low in total fat. No such results have ever been seen with any diet high in saturated fat.
Choose foods close to nature, mostly plants- and you will avoid a host of ills, from the wrong kinds of fat, to excesses of sugar, salt, starch, and calories. By choosing wholesome foods, you construct a wholesome diet- with a good chance of adding both years to your life, and life to your years. Vegetables, fruits, whole grains, lentils, beans, nuts, seeds, olives, avocados and fish are all among the foods most decisively recommended for health promotion, and all are low in saturated fat. That is by no means their only virtue, but it is among them.
While the science has moved incrementally into the realm of subtleties, we have remained mired in pop-culture fickleness about nutrition. But look around, and you will see what a fat lot of good it has done us to fall in and out of love with entire macronutrient classes!
Shifting that silliness to sub-classes, such as saturated fat, will do us no more good- so let’s not. Instead, let’s learn from the follies of nutritional history, and avoid repeating them.
Dr. David L. Katz; www.davidkatzmd.com