In Good Food, a recently-published book, the eminent physician Dr John McKenna cast doubt on the long-held consensus that there is a link between dietary fat and heart disease. But does this opinion stand up to scrutiny? And if it does, what does this imply for the low-fat diet I and many other type 2 diabetics are using to beat our diabetes?
Fats come in two main types: unsaturated and saturated.
The main difference between them is that unsaturated fats are liquids at room temperature, whereas saturated fats are solid or semi-solid in the same temperature range.
Unsaturated fats are usually derived from plants and animal sources such as fish. However most fats derived from animal sources (as well as some tropical oils, such as coconut oil) are saturated fats.
The received opinion among the scientific and medical professions is that eating foods high in saturated fats can lead to elevated cholesterol levels in the blood while, on the other hand, the intake of foods containing more unsaturated fats than saturated fats may contribute to reduced blood cholesterol levels.
However saturated fats are vital. Their solidity adds structure to cell membranes, giving them the stiffness and integrity they need. Indeed, most of the fat in a membrane is composed of saturated fat, so you do seem to need some saturated fat in your diet.
However, if you don’t eat enough saturated fats, your body will make them from carbohydrates.
Besides being vital for the structure and function of all cells, saturated fats are needed for the absorption of the fat-soluble vitamins (A, D, E, and K).
In addition, they have anti-microbial properties that protect against harmful microbes in the gut.
They also protect the liver from toxins such as alcohol and, in addition, protect against heart disease by lowering Lipoprotein(a) in the bloodstream. [Lp(a) is an indicator of susceptibility to blocked arteries.]
Why fat was declared bad
The connection between fat in the diet and heart disease has been the subject of scientific studies since World War II, though a link had been suspected long before that.
The Framingham Heart Study is an ongoing project that seeks to identify the common factors that contribute to cardiovascular disease by following the development of the disease in a large group of participants over a long period of time.
Begun in 1948 in the USA, the project is being run jointly by Boston University and the National Heart, Lung and Blood Institute.
In 1961, the project reported a possible link between LDL (bad) cholesterol and heart disease (blocked arteries).
However, according to Dr John McKenna in an article published in the magazine of the Sunday Business Post, a fairly reputable Irish newspaper, on the 22nd September 2013, the lead researcher of Framingham later refuted his own findings, saying that there was no concrete link between dietary fat and heart disease.
Another study Coronary Heat Disease in Seven Countries by Prof Ancel Keys of the University of Minnesota was published in Circulation, a medical journal, in 1970.
The purpose of this long-term study was to prove an association between the intake of animal fat and raised cholesterol levels in the bloodstream, and to prove an association between raised cholesterol levels and heart disease.
The study examined potential risk factors for heart disease among males in Finland, Holland, the USA, Italy, Greece, Yugoslavia and Japan. The men were followed up by researchers every five years to track how many died of heart disease, while their diets and life-styles were analysed for potential risk factors.
The study concluded that high intakes of animal fate raised cholesterol levels which in turn caused heart disease.
As a result of this study the US government recommended that people should reduce their intake of animal fats (found in milk, cheese, cream, butter and eggs).
According to Dr John McKenna, Keys later admitted that the study was flawed and did not show that dietary fat played a role in heart disease.
The rest of the world’s governments went along with the opinion of the US government and began advising their citizens to reduce their consumption of animal fats because of the link between animal fats and heart disease.
Evidence that denies any link between dietary fat and heart disease
According to Dr McKenna, there is plenty of evidence to suggest that there is no link between fat in the diet and heart disease.
For example, there is little heart disease among certain populations that enjoy a high intake of saturated fat, such as the Inuit (Eskimos) of North America, the French and the Masai.
In fact, among Europeans, the French have the highest level of saturated fat in their diet but the lowest incidence of heart disease.
And the Masai in East Africa do not have any heart disease at all even though they have more saturated fat and cholesterol in their diet than all other population groups, according to a study by Dr George Mann published in the American Journal of Epidemiology in 1972.
The problem with this kind of macro-evidence is that there may be other factors in the environment or diet of the populations studied that reduce the incidence of heart disease.
During the 1940s and early 1950s, people in Britain ate very little saturated fat because of war-time rationing, so if there was a link between saturated fat and heart disease one would expect the incidence of heart disease to fall. In fact it trebled during this period.
But this does not refute the link. The rise in heart disease was probably due to stress … the stress of being bombed during World War II and the deprivations that persisted for years afterwards.
Over the last 30 years or so the advice given to Westerners has been to eat a low fat diet, yet the incidence of heart disease has not altered significantly during that time. Does this disprove the link? I don’t think so. It may merely show that the advice was not being followed.
Nevertheless, several prominent doctors have used this kind of evidence to disavow the link. Prof Michael Oliver, past-president of the Royal College of Physicians in Britain, has stated that there is no hard evidence linking dietary fat and heart disease.
Implications for beating diabetes
So is there a link between dietary fat and heart disease? I don’t know. The evidence is contradictory and the opinions expressed by the scientific establishment are becoming confusing.
However I feel that, for a type 2 diabetic who is trying to control his or her glucose levels using the low-fat diet I have found so successful, the question is irrelevant.
The theory underlying my diet to beat type 2 diabetes is that fat is blocking the receptors in muscle cells. This, to me, is the essential problem of type 2 diabetes.
The fat prevents insulin from attaching itself to the receptors so it can induce the cell membranes to open to allow the glucose released by the digestive process to enter the cells. The result is insulin insensitivity.
My answer to that problem is to reduce the fat in my diet, whether saturated or unsaturated, to as little as possible. For me, and many others, this diet is working to control our diabetes.
Most diabetics who do not control their blood glucose levels are killed by heart disease. So it seems to me that reducing the fat in your diet is vital, even if saturated fats are necessary for the structure and function of cells.
After all, the body can produce the saturated fats it needs from the carbohydrates you eat.