Have you eaten a lot of fatty meats and high-fat dairy products such as butter and sour cream the past couple of days? If you celebrate Christmas, then chances are the answer to that question is yes. Perhaps no other holiday is as heavy on saturated fatty acids – the dominant type of fatty acids found in sausages, ribs, bacon, butter, sour cream, crème fraîche, and the like – as Christmas
This begs the question: Are we harming our bodies by consuming a lot of those foods? If you ask an Atkins devotee this question, the answer you’ll receive will probably be a resounding no. If you ask a nutritionist, dietitian, or nutritional scientist, however, the answer will with a high degree of certainty be yes. He or she will probably tell you that you shouldn’t be afraid to enjoy yourself during the holidays, but that you would be wise to keep large quantities of saturated fatty acids from entering your habitual diet.
If you’ve been hanging out in the low-carb section of the nutritional community for some time and listened to the preachings of advocates of very fatty diets, you may have been left with the impression that the above recommendation isn’t based on solid science. The reality, however, is that it is. Actually, I would go as far to say that the science on this matter is clear-cut: it is unwise to take in large quantities of saturated lipids.
In my previous articles on this topic (e.g., this one, this one, and this one), I’ve presented a wealth of scientific evidence in support of this notion, including evidence pertaining to the evolution of the human diet. In today’s article, I’m not going to completely submerge myself into the science on this matter again. What I thought I’d do instead is to have a look at some brand new research that is relevant to the discussion of how saturated fats affect our health.
A new systematic review and meta-analysis adds to the pile of research indicating that saturated fat is guilty of many of its alleged crimes
Last month, a systematic review and meta-analysis of randomized controlled trials and prospective cohort studies entitled Health effects of saturated and trans-fatty acid intake in children and adolescents: Systematic review and meta-analysis was published in the scientific journal PLOS ONE. This is one of the latest additions to the long list of research papers that all indicate that diets high in saturated fat are less than ideal with respects to their impact on blood lipid levels, blood pressure, and general health.
Here’s what the analysis showed:
This systematic review and meta-analysis showed that reduction of SFA [Saturated Fatty Acid] intake in children and adolescents between 2 to 19 years of age was associated with statistically significant reductions in total and LDL [Low-Density Lipoprotein] cholesterol and diastolic blood pressure. These effects were consistent across all of the trials included in the meta-analyses. The effects on cholesterol were greatest among those in which SFA was replaced primarily with PUFA [Polyunsaturated Fatty Acids] or MUFA [Monounsaturated Fatty Acids], and when the intervention group achieved a reduction in SFA to below 10% of total energy intake. (1)
In the discussion section of the paper, the authors also get into the health effects of saturated fat consumption in adults. The following two sentences are particularly relevant to this post:
There is strong evidence from controlled clinical trials in adults that replacing dietary SFA with MUFA, PUFA or carbohydrate reduces total and LDL cholesterol concentrations. In addition there is reasonably strong evidence from randomised trials in adults that replacing SFA with PUFA from plant oils, but not refined carbohydrates, reduces the incidence of cardiovascular events and mortality. (1)
Hunter-gatherers have markedly lower total cholesterol and LDL levels than industrialized humans (2). This is undoubtedly one of the reasons why cardiovascular disease, hypertension, and many other health problems that are highly prevalent in industrialized nations are absent among forager populations. In particular low LDL levels are important in this respect, as highlighted by the following quote:
Innumerable epidemiological studies have shown a positive relationship between serum cholesterol levels and risk for CAD [Coronary Artery Disease]. In fact, the link between cholesterol and coronary artery disease is one of the most thoroughly researched and established facts in all of medicine. There is overwhelming evidence, accumulated over more than two decades, to show that the more you lower LDL cholesterol, the lower your risk. For every 1 mmol/l reduction in LDL-C using statins, the most powerful drugs we currently have for lowering LDL cholesterol levels, there is an approximately 12% reduction in total mortality and a 21% reduction in major vascular events. (3)
It’s difficult to scientifically assess how a change in a single dietary variable such as saturated fat intake affects human health and longevity, in large part because human diets consist of foods, not of isolated nutrients, and because it takes many years for degenerative diseases such as heart disease to develop. This helps explain why not all studies that have looked into the health effects of saturated fat consumption show similar results. It also highlights the fact that it’s important to be careful when one interprets the results of nutritional research that deals with nutrient-health relationships. This is true even if the research in question is a meta-analysis that combines the results of many similar studies.
One of the main limitations of the systematic review and meta-analysis that is at the center of this article is that it doesn’t include hard cardiovascular endpoints; it relies on surrogate markers. Moreover, it doesn’t distinguish between small and large LDL particles. By itself, the study doesn’t provide conclusive proof that diets high in saturated fat are unhealthy. However, when it’s combined with all of the other research on this matter, including recent research papers such as this one, this one, this one, and this one, the only conclusion any rational person can come to is arguably that a high intake of saturated fat is problematic in terms of its impact on health.
There is a discrepancy between what the science shows and what many low-carbers and evolutionary health aficionados believe with respects to the health effects of saturated fat consumption
If you’ve regularly been dropping by Darwinian-Medicine.com these past couple of years, you’ve probably noticed that I’ve published a number of articles on saturated fat. The reason why I’ve devoted quite a bit of time to talking about this type of fat is not that I have a deep hatred for fatty acids of the saturated kind, but rather that I feel the recent “uprising” against the long-standing public health advice to limit the consumption of saturated fat is misguided. It has become trendy to bring more saturated fat into one’s diet and lash out against people who are reluctant to abandon the idea that it’s unwise to take in a lot of saturated lipids.
My impression is that a lot of low-carb dieters and people who are involved in the evolutionary health community think that saturated fat is, in the grand scheme of things, benign. The vast majority of nutritional scientists, as well as nutritionists (including myself) and dietitians, on the other hand, don’t hold this belief. They favor diets that are fairly low in saturated fatty acids over diets that are high in them.
The fact that this is the general consensus among scientists and people who are formally trained in diet and health related matters doesn’t necessarily make it correct; however, I’d argue that it should cause us to pause before we join those who fight to get saturated fat cleared of all of its suspected wrongdoings. I don’t agree with the nutritional establishment in everything; however, when it comes to the health effects of saturated fat consumption, I think the establishment is more on the right tracks than those who carry on the legacy of Dr. Atkins.
With that being said, as I’ve pointed out in almost all of my previous articles on this topic, there’s no reason to shun all foods that contain saturated fatty acids. Saturated fat is a natural part of healthy whole foods such as unprocessed grass-fed meat (including organ meats) and eggs. What’s important to point out though is that these foods contain relatively little saturated fat when compared to butter, ghee, cream, sausages, cheese, and the like, which, in my opinion, it’s wise to limit one’s consumption of.