The main thrust of the healthy eating recommendations which have been promulgated as official policy for the past 40 years or so has been to reduce the intake of total fat, especially the saturated fats (SFAs). Numerous evaluations of the rationale to support this advice have concluded that it was fundamentally flawed. What is more, there are convincing reasons to believe that those who complied have damaged their health because of the changes they made to their habitual diet. In particular, the increase in the consumption in sugar and other carbohydrate-containing foods is probably why there has been such a disastrous increase in the incidence of obesity, Type 2 Diabetes (T2D) and related conditions.
The most recent study has just been published in the BMJ (1). It has been conducted by a team of researchers based in Canada. The object of the investigation was to do a systematic review of the associations between the intakes of SFAs and the trans fatty acids (TFAs) with respect to all-cause mortality (ACM) as well as cardiovascular disease (CVD), coronary heart disease (CHD), stroke and T2D.
This type of work has been bedevilled by misuse of associations because there are far too many examples of wrongly using this type of information to conclude that there is cause and effect. So if there is no association it is highly unlikely that there is a cause and effect.
The main focus of this blog will be on ACM because that is the prime concern of most people. In the past there has been too much emphasis on a single disease such as CHD to the exclusion of all others. It now evident that those who were pushing the “cholesterol theory” totally ignored the increase in the incidence of cancer which is invariably observed at low values of blood cholesterol and LDL cholesterol.
Here are some of the key results from the Canadian study:
- For the studies on SFAs, the team started out with 20,413 potentially eligible articles. These were ultimately whittled down to 6 which met the stringent criteria that had been established.
- There was no association between SFA intake and ACM.
- There were a few studies which suggested that ACM increases at high intakes of TFAs. However there was reliable and strong positive associations between TFA intake and CHD and CHD mortality which was consistent with several previous systematic reviews and meta-analyses. TFAs may cause inflammation, which can be the starting point for many chronic diseases.
- The damage to health was restricted to TFAs produce by industrial processes. There was no indication of increased risks associated with the TFAs present in cows’ milk.
Any attempt to establish the facts in this field is beset with difficulties, which are rarely appreciated by the researchers so the reality is that many of the studies are very poor and should never have been used as a basis for the development of policies. First of all, there are many different individual saturated fatty acids and it certainly cannot be assumed that they all have a similar function in the body. In fact it would be remarkable if they did. The number of carbon atoms can vary from 1 or 2 up to 20 or more. There is convincing evidence that the short and medium chain fatty acids (MCTs) are especially valuable nutrients. This is because they do not need to be emulsified by bile salts and so are rapidly absorbed into the blood stream from the small intestine. They are especially valuable because they boost the immune system and possess anti-microbial, anti-viral and anti-tumour properties. Lauric acid (C12) is particularly effective.
Much of the case used to condemn the SFA is based on some rather dubious studies which conclude that the SFAs “lower cholesterol” but again it depends on which individual fatty acid is being considered. It is recognized that certain ones such as stearic acid (C18) does not have any effect. But all this is only of academic interest since it is now known that the ACM is raised at low values of both Total Cholesterol and LDL Cholesterol in the blood (2, 3).
The source of SFAs used in the different studies can actually vary considerably. In some, fat from animal products has been wrongly labelled as saturated so results from this type of investigation are quite meaningless.
It is also crucial to allow for the effect of other nutrients which may be present. The Canadians note that there were differences between studies on T2D. In one of these adjustments had been made for the magnesium and fibre levels in the diets but in the other this had not been done. It was also found that replacing the SFAs with either carbohydrates or other fats produced differences in the results.
It is significant that there the case for lowering the intake of the SFAs has been found wanting when subjected to rigorous examination. In recent years, there have been several studies which have all come to the same conclusion. Earlier this year Zoe Harcombe and colleagues analysed the results of all the studies which had been done prior to the introduction of the recommendation to reduce SFAs in 1983 (4). They found that there were no differences in all-cause mortality and non-significant differences in CHD mortality, resulting from the dietary interventions. Although there were reductions in mean serum cholesterol levels which were significantly higher in the intervention groups, this did not result in significant differences in CHD or all-cause mortality.
An earlier meta-analysis conducted in 2010 concluded that there was:
“no significant evidence to conclude that dietary saturated fat(SFA) is associated with an increased risk of CHD, stroke or CVD” (5).
Despite all this the UK Government carries on with its discredited policies. In a response to a letter from me forwarded by my MP to the Health Minister. The reply from the one of the junior ministers, Jane Ellison, contained the following statement:
“There is good evidence that saturated fat consumption influences serum cholesterol levels and thereby increases the risk of cardiovascular disease. On this basis, the PHE will continue to advise people to consume a diet that is low in saturated fat”
What a load of absolute rubbish!!