We wanted to find out the effects on health of cutting down on saturated fat in our food (replacing animal fats with plant oils, unsaturated spreads and more starchy foods).
We assessed the effect of cutting down the amount of saturated fat we eat on health outcomes including dying, heart disease, stroke and cancer for at least two years. We only looked at studies of adults (18 years or older). This included men and women with and without cardiovascular disease. We did not include studies of acutely ill people or pregnant or breastfeeding women.
The review found that cutting down on saturated fat led to a 17% reduction in the risk of cardiovascular disease (including heart disease and strokes), but no effects on the risk of dying. The review found no clear health benefits of replacing saturated fats with starchy foods or protein.
The first thing that strikes me about the author’s self-described “Key results” is that “cutting down on saturated fat” (whatever “cutting down” means) has “no effects on the risk of dying”. This study shows no effect of intervention (i.e., reducing sat fat) on all-cause mortality, cardiovascular mortality, myocardial infarctions (MI), non-fatal MI, stroke, coronary heart disease mortality, and coronary heart disease events. What’s the point of “cutting down” if it doesn’t change the risk of dying?
The second thing that jumps out is the stated 17% reduction in the risk of CVD. Therefore, even though your risk of dying doesn’t change (as referenced above), at least you get some added protection against CVD, right? And that seems like a significant benefit until you realize the authors have chosen to highlight the relative risk versus the absolute risk. I’m not going to go into a deep discussion of statistical analysis, but I am confident that the actual number of people who reduced their risk of CVD by being part of the groups who reduced their saturated fat in the various studies was very, very small in relation to the actual number of people in the other groups in the studies (e.g., a control group) who reduced their risk of CVD.
JBean, did you look at Table 6 in this Cochrane review?
Of the 13 studies they choose to include, one of the studies is the Oslo Diet Heart Study. Apart from the fact that it’s from 1966 and doesn’t control for transfat, that study is acknowledged as multifactorial (i.e., the Oslo Diet wasn’t just about fat and the Oslo Diet study factored in things like exercise). In addition, the study was men only. Finally, and most importantly, there were 412 participants (all of whom had a previous heart attack), but the Oslo study only contains dietary information from 17 participants. How can you possibly draw conclusions about saturated fat reduction from that information?
There are serious flaws with some of the other studies included in that Cochrane review, but I’m going to pass on further comments except to say that from what I can tell, none of the studies were about saturated fat in isolation. They were all comparative (e.g., sat fat versus PUFA) and provide little information as to sugar reduction along with fat reduction.
In closing, I want to go back to one of the “Key results” that said: “The review found no clear health benefits of replacing saturated fats with starchy foods or protein.” This result is particularly on point for this discussion because the study said there was no benefit from replacing saturated fat with carbohydrates EVEN WHEN IT LOWERS CHOLESTEROL. If cholesterol is the issue, then that wouldn’t be true.