So said the late Francis Crick, who along with James Watson worked out the basic structure of DNA in the early 1950s. His remark was quoted in a 1978 New Yorker article on the history of DNA (sometimes I get a tad behind in my reading, and this article, yellowed with age, was close to, although not at the bottom of, my "To Read" pile).

It's too bad the American Diabetes Association doesn't follow Crick's sage advice. It's hampering their progress and destroying their reputation in the minds of many people with diabetes.

Real science operates as Crick suggested. You have an idea, and you test it to see if it's true. If it is, you then try to refine your idea, or you let other people do that and you move on to a new idea.

If the experimental results show you're wrong, you reject your first idea and try to come up with a better one. You don't hang on to some old theory, for example that the earth is flat, simply because you've invested a lot in promoting that idea. If it's wrong, it's wrong. Admit it and move on.

In the early part of the 20th century, the standard treatment for all types of diabetes -- they didn't even know then that there were several different types, just "mild diabetes" (type 2) and life-threatening diabetes (type 1) -- was a low-carbohydrate, high-fat diet.

Then in the 1950s, when the results of Ancel Keys's studies appeared to show that diets with a lot of saturated fat increased risks of heart disease, the ADA started promoting low-fat diets for people with diabetes, who are at very high risk of heart disease. Because they also thought high-protein diets caused kidney disease, the only major nutrient left was carbohydrate, so the diets they supported were 60% to 70% carbohydrate.

"Make starch the star!" people were told by dieticians and ADA publications. "The more carbohydrates you eat, the better," the authors of a popular book on the glycemic index advised people with diabetes.

Of course, everyone knows it's carbohydrates that make blood glucose (BG) levels rise. But before the landmark Diabetes Control and Complications trial results reported in 1993, doctors didn't even believe that high BG levels were what caused complications. Even after that became clear, some doctors told their patients that fat intake was the central problem and that they should control BG levels with drugs, including insulin.

This low-fat mania led dieticians to suggest that people both with and without diabetes eat high-carb meals: a typical low-fat breakfast might consist of cereal, skim milk, toast (no butter), fruit, and orange juice, a veritable carbohydrate avalanche. After such meals, those with diabetes often didn't test their BG levels until just before lunch, when the tremendous peaks the carbohydrates caused had mostly come down.