There exists a systematic misunderstanding of the role of nutrition in the modulation of blood cholesterol levels. While it is a widely held belief that saturated fat and cholesterol in the diet negatively affect blood cholesterol levels, this assertion is not supported by the evidence in the nutritional literature. However, researchers perpetuate the myth by publishing poor quality science, that passes peer review, presumably because the reviewers simply do not understand the science or the methodology they are reviewing. These studies are then cited by other studies (often from the same authors), perpetuating the misunderstandings from the original source. These papers are often cited continually, and in this way academics become imprisoned in an echo chamber of unsubstantiated claims, that creates a castle of knowledge built upon a foundation of sand. For example, one study1 (see figure 1 and 2), based its entire background premise on two previous studies (from the same research group) showing that saturated fat detrimentally modulates blood cholesterol. For the background evidence two citations are given.
Figure 1. Original paper front page.
Figure 2. Citations used to claim that saturated fat detrimentally raises plasma cholesterol levels. Interestingly, both these papers are from the same research group.
The only problem is that the citations do not support the contention that saturated fat is able to raise blood levels of cholesterol. In the first study (Bjermo et al, 2012) the authors used obese subjects, 15 % of which were diabetic. These were therefore not healthy subjects and conclusions about changes observed throughout the study should therefore not be extrapolated to healthy subjects. Further, the study changed the entire diets of the subjects, including the fat composition, and so it is not possible to state which change to the diet was the cause of the effects. In particular, the foods included in the high polyunsaturated fatty acid diet, could have lowered plasma cholesterol levels for reasons other than the fat composition. High polyunsaturated fatty acid diets for example tend to be higher in fibre (as plants containing polyunsaturated fats also contain fibre) and contain plant sterols, both of which are potent cholesterol lowering agents. From this study, it is therefore not possible to conclude that polyunsaturated fatty acids lower cholesterol in comparison to saturated fatty acids.
In the second study (Iggman et al, 2011), hyperlipidaemic subjects were also used. This indicates that the subjects likely had metabolic syndrome and were therefore not healthy subjects. Again it is therefore not possible to extrapolate these results to normal healthy individuals. Secondly, the subjects again consumed diets that varied in composition, and although the control of the diets was more stringent compared to the Bjermo et al (2012) study, the compositional difference do not allow the effects of the diets to be isolated specifically to the saturated fat component of the diet. For example, the total fibre content of the treatment and control diets were similar, but there is no indication as to which dietary fibres made up the total fibre content. Different dietary fibres can for example have quite different effects on blood cholesterol levels. Further, rapeseed oil, the fat used as the treatment is high in plant sterols, a group of compounds known to decrease blood cholesterol levels. Lastly the essential fatty acid content of the diets differed considerably, and this could have specifically influenced the cholesterol levels of the subjects. It is therefore not possible to conclude from this paper that saturated fat changes blood cholesterol levels.
Dr Robert Barrington’s Nutritional Comments: The theory that saturated fat is the cause of detrimental changes to the cholesterol levels in the blood and that these changes are the cause of cardiovascular disease are an assumption based on a misunderstanding. Not only is there little evidence that saturated fat is the cause of cardiovascular disease, increasingly it is being evidence that sugar may be the real culprit. That saturated fat has been the victim of smear campaign, supported by big business and ramped by complicit researchers, is well evidence and has been reported elsewhere. Anyone who knows the inner workings of the modern media age and the evil machinations of groups of individuals with a vested interest in power and money will probably understand the reasons for this misinformation without the requirement for an explanation. Saturated fat is present in many healthy foods, and when eaten in moderation, there is no nutritional reason not to include it as part of a healthy diet. Balance is the key, everything in moderation and nothing in excess.
RdB
