There is now very convincing evidence that the recommendations to reduce the intake of fat and especially of saturated fat (SFA) have turned out to be one of the most notable failures in the field of public health policy.
As Nina Teicholz (1) and others have shown, the recommendations can be traced back to Ancel Keys, a researcher at Missouri, who was the lead investigator in the Seven Countries Study.This concluded that that there was a direct correlation between the amount of fat/SFA in the diet of different populations, the level of cholesterol in the blood (TC) and the death rate due to heart disease. It is crucial to emphasise that a correlation does not demonstrate “cause and effect”. This is a fundamental error which has been repeated time and time again in the area of human nutrition. Let me explain with a simple example. If there are numerous police cars observed in a location which has high crime, this does not mean that the crime is caused by the police cars. Reducing the number of police cars will certainly not reduce the crime level. Unfortunately there are many conclusions about nutrition which are reached using this kind of irrational logic. However Keys was even worse than this because he manipulated his data. He actually had data from 22 countries but he used information from just 6 countries, which allowed him to demonstrate that the more fat (and SFA) consumed in a country, the higher the death rate attributed to heart disease. He conveniently omitted:
- Countries where people eat a lot of fat but have little heart disease, such as Holland and Norway
- Countries where fat consumption is low but the rate of heart disease is high, such as Chile.
If he had included all his data, then any semblance of a correlation disappeared….the points were all over the place.
For a comprehensive critique of the Seven Countries Study, I can recommend “The Obesity Epidemic” by Zoe Harcombe (2).
Clearly Keys was a very influential in the USA in the sixties and seventies. As a result his views prevailed with the politicians and anyone else who mattered. It is important to appreciate that many distinguished scientists who were opposed to Keys were subjected to a campaign of vilification. John Yudkin, the British nutritionist argued that sugar not fat was the critical factor and was portrayed as a figure of ridicule (3). Keys described Yudkin’s arguments in heart disease “tendentious” and his evidence “flimsy indeed”. Once the policy was in place, it became virtually impossible to criticise it. For example the outstanding nutritionist, David Kritchevsky encountered hysterical opposition which he described to Nina Teicholz as follows:
“People would spit on us! It’s hard to imagine now, the heat of the passion. It was just like we had desecrated the American flag. They were so angry that we were going against the suggestions of the American Heart Association and the National Institutes of Health.”
So for the past 30 years or so the advice to lower the fat/SFA has been promoted very powerfully by the public health authorities, supported by the food and pharmaceutical industries. As a result there has been a shift in food consumption with some of the fat being replaced by sugar and other carbohydrates. Although the driving force for the new recommendations was in the USA, the impact has been felt across the globe, primarily because the position adopted by the World Health Organisation (WHO) which was determined largely by the Americans. Unfortunately many other countries took the lead in formulating nutrition policies from the WHO. There is now widespread acceptance that the increase in the consumption of carbohydrate-foods, especially sugar, is the main factor contributing to the so-called “obesity crisis” (4).
It is absolutely essential that we learn from this episode and try to avoid making the same mistakes again. Regrettably we seem to be incapable of doing so as I will demonstrate by considering another current issue, namely salt.
The official recommendations in the UK are that the population average for adults should be 6g salt per day which translates into 7g/day for men and 5g/day for women (5). The justification is that it will help to lower blood pressure (BP). However it important to note that the reductions which can be achieved by lowering the salt intake are relatively small compared with the levels which are recorded for those suffering from hypertension. It is also assumed that any reduction in BP will result in a corresponding reduction in the risk of heart disease. Furthermore the approach taken by the UK advisory committee has been subject to serious criticism by the Institute of Medicine in the USA (6). On the other hand there are some concerns that there may be dangers in reducing the salt intake to levels that many constitute a danger to health. A recent paper (the PURE study) in the New England Journal of Medicine (6) has collected data on sodium and potassium excretion (to assess the amount consumed) for over 100,000 people in 17 different countries. It was found that those consuming between 7.5 and 15 g salt/day had the lowest risk of death and cardiovascular events. Those with less and those with more had higher values. Clearly we have to be careful about the interpretation of these results. But this study certainly flags up potential dangers. In particular, there is a real possibility that people in the UK who attempt to follow the official advice may finish up with an inadequate intake of salt. If the results of the above study apply to the UK it would mean that current intakes are about right.
Despite this there are some individuals who take a very strong line about salt reduction. At a recent conference Norm Campbell and Graham MacGregor are reported to have stated that:
“Any “controversy” over whether dietary salt is a cause of heart disease and stroke is the result of weak research methodology or commercial interference…”
According to Dr Malcolm Kendrick this can be translated to:
“If you do not believe that excess salt consumption is a cause of heart disease and stroke you are a flawed and misdirected scientist (weak research methodology), or you are corrupt (commercial interference). No other explanation is, of course, possible. You are either an idiot, or corrupt, and therefore – by definition – should be ignored. Or perhaps stoned to death for being an unbeliever.” (8).
The fact that Campbell and MacGregor are also beneficiaries of financial support from various commercial concerns is conveniently not mentioned.
When asked to comment on the PURE study referred to above this is the reaction from Campbell and MacGregor:
“When a member of the audience pointed to the PURE analysis showing that most of the world eats much higher levels of sodium than those recommended by most international organizations, MacGregor and Campbell leaped on this as an example of a study that had radically failed to measure salt in an appropriate fashion, even devising a new “formula” to estimate salt intake because even spot urine testing had been inadequate. “Please let [PURE principal investigator Dr] Salim Yusuf [McMaster University, Hamilton, ON] know that he should stop using spot urine analysis,” MacGregor said curtly.”(9).
Malcolm Kendrick sums it up very nicely
“.. the main point here is the fact that we have more bully boy tactics going on. Two ‘grand fromages’ take the stage to beat the opposition into pulp”.
We know that salt (sodium) is an essential nutrient and that a certain amount must be included in the diet. Very large amounts may be damaging to health. We simply do not know accurately the optimum range of intakes. It may well be that for a substantial proportion of the population, there is no need to alter the intake. Under these circumstances, in my view, it is totally irresponsible to advocate a change. Before any official advice is recommended we have to be certain that there will be an improvement in health as a result. Even more important there must be no possibility that of harm to those who follow the advice.
The parallels with Ancel Keys are much too close for comfort. There is a total failure to try to deal with the actual evidence and the name of the game is to use anything to win your case and denigrate those with the temerity to have a contrary view. It is obvious that there is not a cast iron case for reducing salt. There is a distinct possibility that lowering current intakes may well have a damaging effect. Rather ironically those most at risk would be the people who take the advice seriously and try to comply with the recommendations. We really must learn from the mistakes of the past. The lesson is that we have to have a very convincing rationale before advising how the diet should be changed.
- Nina Teicholz. (2014)“The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet” Simon & Shuster New York
- Zoe Harcombe (2010) “The Obesity Epidemic” Columbus p 87
- Gary Taubes (2007) “The Diet Delusion” Vermillion: London p120
- 9. http://www.medscape.com/viewarticle/826970?src=emailthis