Eggs and Diabetes

Can you eat eggs when you have diabetes? Dr. Jason Fung explains the facts surrounding fat phobia. The lack of evidence that dietary fat is bad for health is an important and credible null result because so much effort was expended looking for proof that dietary fat is bad, by researchers who believed that it is.
In the 1950s, it was imagined that cholesterol circulated and deposited on the arteries much like sludge in a pipe (hence the popular image of dietary fat clogging up the arteries). It was believed that eating saturated fats caused high cholesterol levels, and high cholesterol levels caused heart attacks. This series of conjectures became known as the diet-heart hypothesis. Diets high in saturated fats caused high blood cholesterol levels, which caused heart disease.

The liver manufactures the overwhelming majority—80 percent—of the blood cholesterol, with only 20 percent coming from diet. Cholesterol is often portrayed as some harmful poisonous substance that must be eliminated, but nothing could be farther from the truth. Cholesterol is a key building block in the membranes that surround all the cells in our body. In fact, it’s so vital that every cell in the body except the brain has the ability to make it. If you reduce cholesterol in your diet, your body will simply make more.The Seven Countries Study had two major problems, although neither was very obvious at the time. First, it was a correlation study. As such, its findings could not prove causation. Correlation studies are dangerous because it is very easy to mistakenly draw causal conclusions. However, they are often the only source of long-term data available. It is always important to remember that they can only generate hypotheses to be tested in more rigorous trials. The heart benefit of the low-fat diet was not proven false until 2006 with the publication of the Women’s Health Initiative Dietary Modification Trial and the Low-Fat Dietary Pattern and Risk of Cardiovascular Disease study, some thirty years after the low-fat approach became enshrined in nutritional lore. By that time, like a supertanker, the low-fat movement had gained so much momentum that it was impossible to turn it aside.

The association of heart disease and saturated fat intake is not proof that saturated fat causes heart disease. Some recognized this fatal flaw immediately and argued against making dramatic dietary recommendations based on such flimsy evidence. The seemingly strong link between heart disease and saturated fat consumption was forged with quotation and repetition, not with scientifically sound evidence. There were many possible interpretations of the Seven Countries Study. Animal protein, saturated fats and sugar were all correlated to heart disease. Higher sucrose intake could just as easily have explained the correlation to heart disease, as Dr. Keys himself had acknowledged.

It is also possible that higher intakes of animal protein, saturated fats and sugar are all merely markers of industrialization. Counties with higher levels of industrialization tended to eat more animal products (meat and dairy) and also tended to have higher rates of heart disease. Perhaps it was the processed foods. All of these hypotheses could have been generated from the same data. But what we got was the diet-heart hypothesis and the resulting low-fat crusade.