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Because “Low-Carb” is one of the buzzwords for diets currently, it is important to understand a few things about what carbohydrates are and how they work.

The brain needs carbohydrates to function properly. One of the very important functions of carbohydrates is in assisting the amino acid tryptophan to enter the brain from the bloodstream, allowing it to be converted to serotonin. Serotonin is the neurotransmitter that regulates our moods. The only way we can produce serotonin is by eating tryptophan, which is found in foods containing good quality protein. Low serotonin levels have been associated with depression. If we are not consuming enough carbohydrate, the brain is not able to access enough of the tryptophan we are eating in our food, which can result in low serotonin levels and depression.

There are three types of carbohydrates: Starch, Sugar, and Fiber.


Starchy foods include:

  • Potatoes
  • Wheat
  • Corn
  • Rice
  • Pasta
  • Cereals
  • Bread
  • Crackers


Fiber is found naturally in the plants, nuts and seeds that we eat. Meat and dairy products do not contain fiber. Fiber comes in two types: Soluble and Insoluble. Both types are very important for digestion, and prevention of heart disease, diabetes, obesity and constipation. Some foods contain only one type and some foods, like fruit, usually contain both.

Soluble fibers attract water and form a gel, which slows down digestion. Soluble fiber delays the emptying of your stomach and makes you feel full, which helps control weight. Slower stomach emptying may also affect blood sugar levels and have a beneficial effect on insulin sensitivity, which may help control diabetes. Soluble fibers can also help lower LDL (“bad”) blood cholesterol by interfering with the absorption of dietary cholesterol.

Sources of soluble fiber include:

  • Oatmeal
  • Lentils
  • Apples
  • Oranges
  • Pears
  • Oat bran
  • Strawberries
  • Nuts
  • Flaxseeds
  • Beans
  • Split peas
  • Blueberries
  • Psyllium
  • Cucumbers
  • Celery
  • Carrots

Insoluble Fiber is considered gut-healthy fiber because it has a laxative effect and adds bulk to the diet, helping prevent constipation. These fibers do not dissolve in water, so they pass through the gastrointestinal tract relatively intact, and speed up the passage of food and waste through your gut. Insoluble fibers are mainly found in whole grains and vegetables.

Sources of insoluble fiber include: 

  • Whole grains
  • Wheat bran
  • Corn bran
  • Seeds
  • Nuts
  • Barley
  • Couscous
  • Brown rice
  • Bulgur
  • Zucchini
  • Celery
  • Broccoli
  • Cabbage
  • Onions
  • Tomatoes
  • Carrots
  • Cucumbers
  • Green beans
  • Dark leafy green vegetables
  • Raisins
  • Grapes
  • Fruit
  • Root vegetable skins (such as beets, turnips, potatoes)


Sugar is the third form of carbohydrate and includes several different types. The more common types are sucrose, glucose (also called dextrose), fructose, maltose, and lactose. All forms of sugar occur naturally in foods. In its natural state, sugar is considered unrefined. When sugar is processed from food, it is available to us in more concentrated forms and is called refined sugar.

Sucrose is the most common refined sugar and is what we typically use as granulated sugar for sweetening food, such as cereals, drinks, and for use in baking. Granulated sugar is extracted from both sugarcane and sugar beets. Sugarcane is a tall fibrous grass with sweet juicy stalks. It is grown in tropical and subtropical climates. Sugar beets are large tuberous roots grown in temperate climates in the U.S. as well as other parts of the world. Sugar beets are not the same as the red beets we normally eat. Sugar beets, while they have high sugar content, are unpalatable in their natural state. Sucrose also occurs alongside glucose and fructose in some fruits and vegetables. Molasses is a byproduct of granulated sugar. It is present in sugarcane and is separated in the process of making “white” sugar. Brown sugar is refined sugar that still retains some of the molasses, which is what gives it its brown color. Dark brown sugar has more molasses than light brown sugar. Molasses is the only sweetener that has any appreciable nutritional value but its use is limited due to its strong flavor.

Glucose is produced in fruits and vegetables through the process of photosynthesis. Most ingested carbohydrates are converted to glucose during digestion.

Fructose is the type of sugar in fruit, some root vegetables, and honey. It is the sweetest of the sugars.

Maltose is formed during the fermentation of grains like barley and is converted to malt, which is used as flavoring in drinks and some processed foods. It is less sweet than sucrose, glucose, or fructose. Like glucose, it is formed in the body during digestion of starch.

Lactose is the sugar that is found naturally in milk. It is broken down during digestion by the enzyme lactase, which is present in children but some adults stop producing the enzyme, which results in lactose intolerance, or the inability to digest lactose.


Counting grams of carbohydrate alone is misleading because carbohydrates include fiber. Fiber is not digested and does not break down in the body into glucose like the two other types of carbohydrate, starch and sugar. Both starch and sugar break down into sugar in the body. So, when we eat starchy foods like pasta and potatoes, the starch is converted to sugar in basically the same way as if we ate sugar right off of a spoon. The difference is that the starchy foods have some nutritional value and, oftentimes, some fiber as well. Fiber will slow the process of starch breaking down into sugar, which is good because our blood sugar doesn’t spike. Whereas refined table sugar, has no nutritional value and contains no fiber. So starch is converted to sugar but has some redeeming value. Those are considered “good carbs”. The “good carbs” are the fiber carbohydrates and the starch carbohydrates because they serve important functions and are contained in food along with other beneficial nutrients. That’s one of the reasons whole grains, like whole wheat or brown rice, are a better choice than refined grains, like white flour or white rice. With white flour and white rice, the hulls and bran have been removed from the grains of wheat and brown rice, removing most of the nutrients and the fiber. Most of what you have left is starch. Refined sugar and starchy low-fiber, low-nutrient foods are “bad carbs”.


Limiting “bad” carbohydrates like refined sugar and refined grains is a good choice. Even fruit juices should be limited if a person is concerned about “bad” carbs because they can be high in sugar and low in fiber. When we eat the fruit in its whole, natural state, the sugar occurs in lower concentrations and is consumed along with fiber, allowing the sugar to be broken down more slowly. The fiber also makes us feel full longer.

We need the “good” carbs – whole grains, fruits, and vegetables – for energy as well as our best mental health!




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