The letter relied on long-held, common misconceptions. I am forever reading the scientific literature and, with the help of colleagues, dissecting the internals of any published study.
As a requirement for my degree in nutrition, I learned to analyze the premise, design, methods and conclusions of a study to look for any confounding factors that might contaminate the findings. There are fatal flaws in this letter's logic.
The letter took my statement that dietary cholesterol has no impact on high cholesterol levels out of context. The previous paragraphs discussed the carbohydrate-glucose-insulin connection and, in light of that, my statement remains accurate when accompanied with a low-carbohydrate diet.
In order to prove a theory, we must design a study that meets the requirements of that theory. If you believe that a low-carbohydrate diet allows for daily fat intake between 30 percent and 50 percent of total calories, you would want studies in which the participants consume very low carbohydrates and higher fat levels.
The letter quoted Dr. McDougal, Dr. Neal Barnard and a study from the American Journal of Clinical Nutrition that claim that high levels of fat and cholesterol increase blood cholesterol levels and contribute to heart disease.
The problem is that all the studies that support this claim had no restrictions on the intake of carbohydrates. These studies found a correlation between higher dietary fat and cholesterol levels and increases in cholesterol, triglycerides and LDL levels and decreases in their good cholesterol (HDL): all increased risk factors for heart disease. All studies that have high fat levels and high carbohydrate levels show the same result.
Amazingly, all studies that are designed with low carbohydrate and higher fat intake show normal cholesterol, triglycerides, LDLs and HDLs or the reduction of these risk factors.
The letter also quoted a study that monitored men for 21 days and found increases in dietary cholesterol increased blood cholesterol levels. Again, a study with no criteria for carbohydrate intake. But more interestingly, all short-term studies of less than six months, even those using low carbohydrates coupled with higher fat diets, show some patients have a temporary imbalance of their cholesterol, triglycerides, HDLs and LDLs which normalizes after six months.
Studies have also been done on Mediterranean populations (high fat, low carb diets) and Eskimos, the Masai of East Africa and Icelanders prior to 1930 (all fat and protein diets) and found very low levels of or nonexistent heart disease, high blood pressure, high cholesterol, diabetes, osteoporosis and other chronic illnesses.
The letter states irrefutable evidence links animal fats and total fats to increased risk of lung, breast, colorectal, prostate and pancreatic cancer. The Harvard Nurses Study (1990) apparently confirmed the colorectal cancer connection.
Promoted by a willing media, the design of the study didn't consider total amount of carbohydrate intake. Unreported was breast cancer cases in this study were higher in the lowest fat group and these low fat breast cancer cases outnumbered the high fat colon cases four to one.
Studies done outside the United States (Japan, Belgium and France), all countries with lower average carbohydrate intake, found no connection between high fat and cancer. Here's an interesting fact of physiology: Cancer cells survive on sugar (carbohydrates), not oxygen, as do normal cells.
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In the 1970s, studies showed that high blood insulin levels (caused by insulin resistance) usually accompany high blood pressure (a fact no medical authority has ever disputed), high triglycerides levels and central obesity (weight gain above the waist or an apple shape). In 1985, Dr. Gerald Reaven dubbed this the "Deadly Quartet," and it's now known as "Syndrome X." High blood pressure, high triglycerides and central obesity rarely exist without high insulin levels.
In all fairness, I must also mention studies of low fat, vegetarian diets (vegan or lacto-ovo) show reduced risk for heart disease and other chronic illnesses. Recently Dr. Dean Ornish has shown that a very low-fat lifestyle can reverse heart disease.
So now we appear to have a choice. Would the average person prefer an austere, limited vegetarian diet? Don't get me wrong, I've eaten as a vegetarian and know if you take your time and have the proper knowledge and skills, a vegetarian meal is as mouth-watering as almost any other meal. Unfortunately, the average American doesn't have the time, knowledge or skills; and there's one other problem: People love the taste of fatty foods.
Fat makes meat tender, foods tastier and more satisfying. So where do you think the compliance will be? Sales of low-fat foods have been declining recently. People talk around the water cooler about low-carbohydrate diets, but you never hear them mention Dr. Ornish's low-fat diet. There's a message in there somewhere.
What's irresponsible is the medical establishment maintaining the status quo, considering it's obviously not working. They perpetuate a low-fat diet while never commenting on the influence of carbohydrates. Thirty-five million people in the United States are obese and 40 million have high blood pressure.
High blood pressure is three times more common and high triglycerides twice as common among the obese. We have more low-fat foods in our society than ever before -- and more obese and chronically ill people than ever before. Something's wrong with this picture.
If you have the discipline to undertake a low-fat vegetarian diet (less than 20 percent) with proper caloric intake for your size and activity level, by all means do it. If you prefer the taste pleasures that fat provides, enjoy; but only with a low-carbohydrate diet.
If your diet falls somewhere in between, change it. Your health might depend on it.