It may help you understand unpredictable results. And why we tend to underestimate carbs in large meals.
THE CHINESE RESTAURANT EFFECT
Many years ago a patient asked me why her blood sugar went from 90 mg/dl up to 300 mg/dl every afternoon after she went swimming. I asked what she ate before the swim. “Nothing, just a freebie,” she replied. As it turned out, the “freebie” was lettuce. When I asked her just how much lettuce she was eating before her swims, she replied, “A head.”
A head of lettuce contains about 10 grams of carbohydrate, which can raise a type 1 adult’s blood sugar about 50 mg/dl at most. So what accounts for the other 160 mg/dl rise in her blood sugar?
The explanation lies in what I call the Chinese restaurant effect. Often Chinese restaurant meals contain large amounts of protein or slow-acting, low-carbohydrate foods, such as bean sprouts, bok choy, mushrooms, bamboo shoots, and water chestnuts, that can make you feel full.
How can these low-carbohydrate foods affect blood sugar so dramatically?
The upper part of the small intestine contains cells that release hormones into the bloodstream when they are stretched, as after a meal. These hormones signal the pancreas to produce some insulin to prevent the blood sugar rise that might otherwise follow the digestion of a meal. Large meals will cause greater stretching of the intestinal cells, which in turn will secrete proportionately larger amounts of these hormones. Since a very small amount of insulin released by the pancreas can cause a large drop in blood sugar, the pancreas simultaneously produces the less potent hormone glucagon to offset the potential excess effect of the insulin. If you’re diabetic and deficient in producing insulin, you might not release insulin, but you will still release glucagon, which will cause gluconeogenesis and glycogenolysis and thereby raise your blood sugar. Thus, if you eat enough to feel stuffed, your blood sugar can go up by a large amount, even if you eat something undigestible, such as sawdust.
The first lesson here is: Don’t stuff yourself. The second lesson is:
There’s no such thing as a freebie.* Any solid food that you eat can raise your blood sugar.