The idea that high cholesterol plays a role in the development of heart disease was started by the Framingham Heart Study. This study began in 1948 and monitored 5 000 healthy women and men living in Framingham, Massachusetts, USA. Researchers tried to establish which factors went on to determine if a person suffered a heart attack. High cholesterol was one factor that had some influence on who had a heart attack, but it was only one of 240 risk factors identified. Some other factors that influenced who got a heart attack included short stature, creased earlobes, male baldness, and being married to a highly educated woman!
Cholesterol was latched onto because it is a modifiable risk factor; that means there was an opportunity for drugs to be developed to lower cholesterol. There was potential to make great profits! Many scientists believe the results of the Framingham Study were misinterpreted, and cholesterol has been inappropriately focused on. The study only found an association between cholesterol and heart disease in young and middle-aged men; however over time we have all been instructed to fear cholesterol.
In the late 1950s, researchers came up with the “lipid hypothesis”, also known as the “diet-heart idea”. This claimed there is a direct relationship between the amount of saturated fat and cholesterol in the diet, and the incidence of coronary heart disease. This hypothesis has received much publicity, and is the basis for why low fat, low cholesterol diets are the hallmark of nutrition recommendations. It is also the basis of prescribing cholesterol lowering medication to anyone who has levels above the desired limit.
Since then several researchers have discovered flaws in this hypothesis. Before 1920 heart disease was rare in the United States. This is a period of time when consumption of foods such as butter, lard and dripping was much greater than now; these are all foods very high in cholesterol. Many traditional diets of native populations are very high in fat and cholesterol, yet these populations have very low rates of heart disease.
The Masai tribes of Africa consume a diet of mostly milk, blood and beef; 60 percent of calories they eat are derived from fat. However, the Masai do not have elevated cholesterol, and are free of coronary heart disease. Inuit people (Eskimos) eat an extremely high fat diet; 80 percent of their calories come from fat. These people have healthy blood vessels and there is no evidence they suffered with heart disease. The traditional Australian aboriginal diet contained large amounts of fat in the form of eggs from birds and reptiles, turtles, eels and possums. Many insects are high in fat, such as witchety grubs (67% fat), the green tree ant and bogong moths; their abdomens contain a lot of fat. The aborigines were a fit and healthy population; obesity and diabetes were almost unheard of.
Many researchers believe that it was the introduction of sugar, white flour and alcohol that has led to the explosion of diabetes, obesity and heart disease in this population.
One explanation for this contradiction is that the meat these native populations consumed was quite different in fat composition to the meat we buy from the supermarket or butcher today. Wild game meat is much lower in total fat, and particularly saturated fat than farmed meat. It is also higher in omega 3 essential fatty acids, which help your metabolism. This is why it may be a good idea to include game meat in your diet occasionally such as kangaroo, emu and rabbit. Much of the fresh fish we purchase today is farmed, and unfortunately this type offish is much lower in omega 3 fats than wild fish. This is because it is fed a type of “pet food”, vastly different from the natural diet. Whenever you purchase fish, make sure you ask if it has been farmed or caught wild.
A very interesting study was published in the American Journal of Clinical Nutrition, highlighting the difference in rates of heart disease between people living in northern and southern India. The northerners ate a lot of meat, used ghee in their cooking and had high cholesterol levels. The southerners were predominantly vegetarians, they used vegetable oil and margarine to cook with, and they had lower cholesterol. You may be shocked to know that the vegetarians had a 15 times greater incidence of heart disease than the meat and ghee eaters!
Proponents of the “lipid hypothesis” claim that when our intake of cholesterol and saturated fat is high, the saturated fat is turned into cholesterol which accumulates in the arteries. These deposits of cholesterol get thicker, form a plaque, and eventually narrow the arteries so much that blood flow is restricted. Plaques can also break off and form a blood clot in a vessel.
High levels of HDL “good” cholesterol protect us from heart disease by transporting excess cholesterol away from the arteries to the liver for removal. A high level of LDL “bad” cholesterol means that a lot of cholesterol must be depositing itself on the lining of our arteries, increasing our risk of heart attacks and strokes. This is true to a large extent, but is a very simplistic view of atherosclerosis (formation of fat plaques in the arteries). We now know there are many other factors involved.
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