Saturated Fats and Silly Questions
Updated May 15, 2015.
I imagine those of you who try to follow the latest news on diet and heart health are pretty confused.
One recent study, published in the American Journal of Clinical Nutrition, reaffirmed the association between saturated fat intake, the development of atherosclerosis, and eventual premature death from heart disease among Australian women.
Within a week, another study, published in the Journal of Nutrition, showing no association between saturated fat intake and cardiovascular mortality in Norwegian men and women.
Is this because of some important, and previously unrecognized biological distinction between Australians and Norwegians? No. Is it because we are genuinely confused about the health effects of saturated fat? In my opinion, no.
All it means is that we tend to get answers to exactly the questions we ask, and if the questions are silly, the answers are less than helpful.
The Australian study looked at variation in saturated fat intake among women who did not have heart disease at baseline, and compared that variation to the development of heart disease over time. A higher intake of saturated fat meant a higher risk. The Norwegian study was limited to people who already had heart disease at baseline, and then looked for a differential rate of death from that heart disease in accord with variation in saturated fat intake, finding none.
Let’s consider what might account for differing levels of saturated fat intake among Norwegians with heart disease. There might be a group with strong genetic risk for heart disease, who had a low saturated fat intake all along but developed heart disease anyway.
There is no real surprise that if such people continued their relatively low intake of saturated fat, it would confer limited protection.
Another possibility is that some people reduced their intake of saturated fat somewhat after learning of their diagnosis of heart disease. Since at that point, everyone would be receiving powerful drugs as well, the likelihood of a modest change in saturated fat intake making an appreciable difference in mortality, other things being equal, is rather remote.
If we had to specify exactly what question the Norwegian study answers, then, it would be something like this: does minor variation in saturated fat intake late in life change the death rate in people who already have clinically significant heart disease who are receiving standard, state-of-the-art medical therapy?
Only by clarifying the question a study answers is it possible to know what the answer means. In this case, it means just about nothing regarding the relationship between saturated fat and the risk of heart disease. If a study of minor variations in exercise levels among people with advanced heart failure showed no effect on survival, for instance, it would not disprove the health benefits of exercise. It would simply demonstrate that too little is too late, and too late is too late.
What we really do know about saturated fat and heart disease- based on the weight of evidence rather than any one study or any single, potentially silly question- has four fairly clear implications.
First, a high intake of saturated fat over time is generally associated with a correspondingly higher risk of heart disease, and other chronic disease as well.
Second, a relatively lower intake of saturated fat is not necessarily protective if the saturated fat is replaced with something just as harmful, such as added sugar.
Third, not all saturated fat is created equal, and some varieties are clearly innocuous.
And fourth, and most importantly, focusing on nutrients rather than foods tends to get us into trouble, not out of it!
Personally, I don’t think much about my “saturated fat” intake- but I do choose my foods carefully. I know that the best foods for my health are vegetables, fruits, beans, lentils, whole grains, nuts, and seeds. I eat these plentifully, and relatively less of everything else. The result is that my diet is low in saturated fat- not because I am focused on that, but because eating wholesome foods in sensible combinations reliably results in nutrients sorting themselves out. In contrast, a focus on any particular nutrient may simply invent a new way to eat badly, or a new variety of junk food. We’ve had quite enough of that.
Yes, saturated fat intake is relevant to cardiovascular risk- partly because of direct effects, and partly because a diet that is high in saturated fat is correspondingly low in the very foods that most decisively protect against heart disease.
Answers are ever only as good as the questions we pose. Do we know what dietary pattern is best for health? Good question! We do.