“The Truth About Low Fat Food” is the title of a programme broadcast by Channel 4 on 7th April 2014. This confirms that many “low fat” foods contain more sugar than the corresponding full fat version. Furthermore some of them are surprisingly high in fat and in calories. What I found especially fascinating is that any food which is promoted as “low fat” is perceived as “healthy” and so consumers feel free to consume these in relatively large quantities.
On the other hand the programme appeared to accept that the current official dietary recommendations are sound. For example in an interview with Professor Graham MacGregor, the importance of reducing the amount of in the diet was emphasised. The reality is that the case for reducing total fat in the diet does not stand up to examination. Because fat has been demonised, as the programme correctly demonstrated, those who wish to eat a healthy diet often select the products promoted as “low fat”, which are regarded as healthier than the regular version. Consequently there has been an insidious increase in the amount of sugar consumed, in part because many of the low fat products are devised by removing fat and replacing it with sugar.
Consideration of the history of the evolution of the dietary guidelines reveals that during the 1970s there was a huge debate in the USA about how the diet should be changed in order to reduce the incidence of heart disease. Essentially the question was: “Excess sugar or excess fat?” In the event it was decided that the problem was too much fat, especially saturated fat (SFA). One of the critical factors influencing the decision was the “Diet Heart Cholesterol” theory which effectively means that the concentration of cholesterol in the blood (TC) is a risk factor for heart disease. Hence these risks can be altered by raising or lowering the TC. As it was considered that SFA raised the TC, this meant that dietary SFA was undesirable and should therefore be reduced. Similarly the polyunsaturated fatty acids (PUFA) were supposed to lower the TC which was beneficial and therefore there could be some increase in the amount consumed. Subsequently the rationale which underpins these recommendations has been completely discredited (See refs 2, 3, 4). It is rather significant that a recent report prepared by the British Heart Foundation(BHF)has had to conclude that there is not enough evidence to support the current dietary recommendations to reduce SFA and increase PUFA in order to reduce the risk of heart disease(5).
The BHF report is simply reflecting the finding of a major analysis based on many different epidemiological studies which related the SFA intake to the incidence of cardiovascular disease (CVD). It found that there was:
“no significant evidence to conclude that dietary saturated fat(SFA) is associated with an increased risk of CHD, stroke or CVD”(6).
But it gets even worse because far from being the hazard implied by the official recommendations, there is actually convincing evidence that many of the individual fatty acids are valuable nutrients in their own right.
Here is a brief selection of some of the functions/benefits of SFA (7):
- Cell membranes require SFA to be “waterproof” in order to function properly
- The heart prefers the long chain fatty acids palmitic acid(16 Cs) and stearic acid (18 Cs) to carbohydrates to carbohydrates as a source of energy
- Bones need SFA in order to assimilate calcium effectively.
- The short and medium chain length fatty acids, which have up to 12 carbon atoms 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
- It is now known that the LDL cholesterol exists in particles which vary in size. At one end of the extreme they are densely packed and it is now believed that these particular ones initiate the damage which ultimately results in CHD. At the other end are the large fluffy particles which are relatively benign. SFA in the diet favours the formation of the large particles.
The original doubts about the SFA can be traced back to the concerns that arose in relation to the processing of fats which resulted in the production of the trans fatty acids (TFAs). It is now widely accepted that these are damaging to health. For example TFAs alter enzymes that neutralize carcinogens and increase those that potentiate carcinogens. TFAs can depress milk fat production in nursing mothers and cause abnormal sperm to be produced (8). TFAs are quite different from SFA and there was never any justification for tarring them with the same brush. Fortunately genuine efforts are now being made to eliminate them from the human diet.
In order to complete the picture I need to address the issue of the PUFAs. Because these are actively promoted as beneficial (because they lower cholesterol!) they are considered by many consumers as “healthy”. The truth is they are anything but.
We have to understand that there are 2 families of polyunsaturates…the omega-3s and the omega-6s. Up to about 1900 the diet contained approximately equal amounts of each group. However as industrialisation has progressed the intake of the omega 3s has fallen while that of the omega 6s has increased. As a consequence, the ratio of omega-6:omega-3 is now 15-20 in countries such as the USA and the UK. Excessive amounts of omega-6 PUFA and a very high omega-6:omega-3 ratio promote the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 PUFA (a lower omega-6:omega-3 ratio),exert suppressive effects
Virtually all those products which claim to lower TC are omega-6. This means that the more of these a person consumes the more the ratio of the two gets out of kilter (9). As I have explained above the cholesterol theory no longer holds water and therefore the case for consuming these products has been destroyed.
When all else fails the advocates for low fat resort to the simple calories in-calories our argument. Essentially this is that because fat is a concentrated source of energy (calories) we must reduce it in order to prevent obesity. So just consider what has happened in Great Britain over the past 50 years or so. National statistics show that amount of fat consumed has fallen from 120gm/day in 1969 to 74gm/day in 2000. When expressed as a proportion of energy consumed the fat intake has decreased from 42.6% in 1980 to 37.7% Calories in 2010.At the same time there has been an increase in the energy as carbohydrate from 44.4 to 47.4%. Consideration of the different types of fats shows that between 1969 and 2000 the intake of saturated fat (SFA) has fallen from 56.7 to 29.2 g/day. In other words it has been reduced by almost half (10). As we are only too well aware, over the same period the incidence of obesity has increased. Since 1994 obesity has doubled in men and increased by 60% in women. Even more worrying is that diabetes has more than doubled in both men and women over the same period. In the light of these results can there be any possible justification for continuing to advocate a reduction in fat? What should be obvious to anyone who looks objectively at the research and the current state of public health is that we must focus on the carbohydrates, especially the sugar.
The big problem is that “the great and the good” in the public health and medical professions are unwilling to admit that they have been wrong about the recommendations on fat. While it is encouraging that the concern about sugar is now being recognized we will not make significant progress until people are provided with accurate advice about fat in general and the different types of fat in particular.
If the Dispatches team on Channel 4 really wishes to get to grips with the key nutrition issues then they should be asking the Government why it continues to advocate a reduction in fat, especially SFA, when there is no reliable evidence to justify this policy. In fact these recommendations are fundamentally flawed and are effectively a major contributor to the current poor standard of public health as shown by the statistics on heart disease, diabetes and cancer.
- P. Siri-Tarino (2010) American Journal of Clinical Nutrition 91 (3) pp. 535-546
- Mary Enig(2000) “The Skinny on Fats” http://www.westonaprice.org/know-your-fats/skinny-on-fats?