Many say low-carbohydrate eating controls diabetes. Others say such diets are unhealthy or impractical. But what does “low-carb” mean? If you want low-carb, what can you eat, and how much? Let’s see.
I’ll admit that, right now, I don’t have the answers. But I do have time to read books and search the Internet, and Diabetes Self-Management hired me to do it. So hopefully, over the next few weeks, I can give you some useful information.
You might find some of this old news, but I’d like to start with the basics. First, scientifically speaking, what are carbohydrates? According to Wikipedia, a carbohydrate is an “organic compound that consists only of carbon, hydrogen, and oxygen,” usually with two hydrogen atoms to one oxygen atom. So basically, they’re carbon and water.
Kind of incredible what Nature can do with those simple building blocks. Plants make carbs by combining carbon dioxide and water with the help of energy from the sun. The sun is the source of the energy carbs provide. All plant foods except seeds are mostly or completely carbohydrate.
In biology, carbohydrates are also called saccharides. There are four kinds. Two of them, monosaccharides and disaccharides, are usually called sugars. (“Saccharide” comes from the Greek word for sugar.) Most mono- and disaccharides have chemical names ending in “-ose,” like lactose (milk sugar), glucose, and sucrose (table sugar.)
Other carbs are called “polysaccharides,” more often called “starches.” The body can easily break starches down into sugars for energy. If you hold a piece of bread in your mouth, it becomes sweeter and sweeter. That’s because saliva enzymes are turning the starch into glucose.
The last types of carb are the “oligosaccharides” which make up much of the fiber we get in vegetables and other plant foods.
Carbs in the body
Mono- and disaccharides are many people’s main source of fuel. However, various food scientists say carbohydrates are not vital, because the body, except for the nerves, can get its fuel from protein and fats. The nervous system can’t use fat for energy, but can use ketones, which come from the breakdown of protein. That’s why some people can stay healthy without any carbs at all, as the Eskimos did when eating their native diet, and as some low-carb fanatics do now.
After being digested, most carbs (except for fiber) turn into glucose and are used for fuel. Some can’t be used, usually because cells already have all the fuel they need. The unused glucose can be converted into starch (glycogen) and stored for times of high energy use, like a long run or skipped meal. Or it can be converted into fat for long-term storage in case of famine.
Certain carbs do have other functions. One is deoxyribose, which is a major component of our bodies’ genetic material, DNA. Some oligosaccharides appear to help sperm and ova come together for reproduction. Fiber has numerous benefits, which I documented here.
Carbs and diabetes
Since the main function of carbohydrates is to provide glucose for fuel, when you eat them, your blood glucose will go up temporarily. Everyone’s does; it’s not open to question. But how much it goes up, and how long it stays up, varies according to many factors. The biggest factor, by far, is diabetes.
In a person without diabetes or prediabetes, insulin will rush into the blood at the first sign of carbohydrates. As the body absorbs carbs, the insulin will grab the glucose and take it to the cells, to be used as fuel or stored. So blood glucose typically will not go above 140 milligrams per deciliter (mg/dl).
But a person with diabetes has less insulin, and what they have doesn’t work well, because of insulin resistance in the cells. Something is wrong in one or more parts of the insulin system. Without effective insulin, glucose stays in the blood until the kidneys excrete it in the urine. So glucose levels can go above 200 mg/dl, sometimes far higher, and they can stay there for a long time.
Injecting premeal insulin helps, but it doesn’t solve the problem of insulin resistance, and it increases the risk of low blood glucose (hypoglycemia), which also causes damage. Other medicines also help, but none can really manage the high glucose levels that many carbs produce.
High glucose levels after eating are the cause of most of the complications of diabetes. Those high glucose levels damage nerves and blood vessels. Insulin-producing beta cells also start to die off when glucose stays above 110 mg/dl. This is probably why diabetes progresses over time. Fewer healthy beta cells mean less effective insulin will be produced.
You can see numerous studies documenting the effects of glucose levels above 140 mg/dl on Jenny Ruhl’s site Blood Sugar 101.
Now, since carbohydrates turn into glucose, and people with diabetes don’t have the effective insulin to use the glucose, and too much glucose makes us sick, we probably should consume less of them. But that’s a lot easier said than done, or even understood.
As I mentioned, most plant foods are largely made of carbs. Do we have to avoid breads, fruits, vegetables, everything that grows? Are we supposed to eat nothing but meat? That can’t be healthy for us, for the animals, or for the planet. So what ARE we supposed to do?
Dozens of low-carb diets have been recommended. But there are so many of them, and so many questions.
First, how much carbohydrate is low-carb? Next week I’ll go over various recommendations for how much carbohydrate to eat, and what types. Then we can talk about the best ways to consume fewer carbs, and how to decide for yourself if you want to do that.
It would really help the discussion to hear what your experiences have been, and what knowledge you have gained. Thank you for contributing.
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