What is a Carb? The Skinny on Carbohydrates

Patients often ask me to better identify how to consume healthy carbs and the right amounts in their diet. Americans have caught on that refined carbohydrates are a big factor for the weight and diabetes problem in America.

So what is a carb?

A carbohydrate is a compound that contains carbon and water molecules. Actually, individual sugar molecules joined together make up carbohydrates. The simplest of sugar molecules are glucose, fructose (fruit sugar), and galactose (a milk sugar). These are known as monosaccharides, as they each contain one sugar molecule. Within the category of carbohydrates are simple and complex carbohydrates. Examples of simple carbohydrates include table sugar, honey, and fruit sugars.

As you know, most people consume far too many simple carbohydrates. Although the body ultimately breaks carbohydrates down into glucose (the simplest of sugars), most simple carbohydrates, like candy, potato chips, soda, and refined flours (white breads, crackers, chips, cookies, muffins), have little-to-no fiber, vitamins, minerals, or phytonutrients. These carbohydrates are often called empty calories. When consumed in excess, especially on an empty stomach, they lead to immune system suppression, mood swings, attention problems, and weight gain (fat deposition). Many of these effects are due in large part to the spike in blood sugar that results after they are eaten. As a result, the hormone insulin is released to help transport blood sugar to the cells. As a by-product of this, the pancreas (which produces insulin) is overtaxed, immune cells are weakened, and the body stores fat.

Too high a percentage of simple carbohydrates in the diet predisposes people to develop obesity, diabetes, cavities, and heart disease. The question then arises: What about fruits, because most of them contain simple carbohydrates? Research has shown that many types of fruits are good to eat, when consumed in moderation. As it turns out, fruits contain a great deal of fructose. This simple sugar does not cause a rapid rise in glucose and insulin levels because fructose must first be converted into glucose by the liver, to be available for the body to use. Fructose has a much more stable effect on blood-sugar levels than other common sugars, such as sucrose, maltose (found in rice syrup and malt), dextrose, and honey. Certain fruits, such as apples, contain fiber that helps to normalize blood-sugar levels.

Glycemic Index

Glycemic index (GI) has become a popular term; it is more meaningful than the label simple carbohydrate. GI refers to the rise in your blood sugar after you ingest a specific food. This numerical value is compared to the GI of glucose at a value of 100. It is recommended that people with obesity, diabetes, and insulin resistance eat foods that have lower glycemic values. For example, a Coca-Cola soft drink has a glycemic index of 63, whereas as a serving of kidney beans has a value of 23.  Patients are always shocked to find out that whole wheat flour bread(due to modern hybridization and baking practices) has a GI of 71!

  • A GI of 70 or more is considered high.
  • A GI of 56 to 69 is considered medium.
  • A GI of less than 55 is considered low.

Glycemic Load

Recently, doctors and researchers have placed more value on the glycemic load (GL) value of foods. The glycemic load takes into account the amount of carbohydrates in one serving of a particular food. The glycemic index tells us how quickly a carbohydrate turns into blood sugar, but it neglects to take into account the amount of carbohydrates in a serving, which is important. The higher the glycemic load value, the higher the blood-sugar level and the resulting stress on insulin levels. This value is derived by multiplying the amount of carbohydrates contained in a specified serving size of the food by the glycemic index value of that food, and then dividing by 100. For example, an apple has a GI of 40, compared to that of glucose, which is the baseline at 100, but the amount of carbohydrates available in a typical apple is 16 grams. The GL is calculated by multiplying the 16 grams of available carbohydrates times 40 and then divided by 100, to arrive at a decimal number of approximately 6. Compare this to a serving of Rice Krispies, which has a glycemic index of 82 and 26 available carbohydrates and has a glycemic load of 21. And a serving of macaroni and cheese has a glycemic load of 32.

  • A GL of 20 or more is considered high.
  • A GL of 11 to 19 is considered medium.
  • A GL of 10 or less is considered low.

For a rating of Glycemic Index and Glycemic Load, see Harvard’s ratings.

Good carbs?

Complex carbohydrates should be the dominant type of carbohydrates in the diet. They provide a longer-lasting energy source, help us to feel fuller, maintain our blood-sugar balance, contain fiber that helps us with elimination, and contain more vitamins, minerals, and phytonutrients than simple carbohydrates do. Examples of complex carbohydrates include whole grains (such as whole wheat pasta, whole grain breads and cereals, and oatmeal), beans, brown rice, peas, and most root vegetables.

Consuming carbohydrates along with protein, fiber, and fat (good fats) helps to smooth out their effect on blood-sugar levels. This is another reason why a balance of all the nutrients is so important.