Known also as saccharides, carbohydrates are macronutrients. Approximately 2% of the body weight is carbohydrates. They should constitute about 50% - 55% of total daily calories intake.

Carbohydrates are classified into three groups: monosaccharides, oligosaccharides, and polysaccharides.

Monosaccharides contain only one subunit of sugar and they represent the basic units of all carbohydrates.

Oligosaccharides contain 2 – 10 monosaccharides, and their major group is disaccharides or double sugars. Monosaccharides and disaccharides are collectively called simple carbohydrates.Polysaccharides are composed of more than 10 monosaccharides.

Types of Carbohydrates:
Monosaccharides	Disaccharides	Polysaccharides
Glucose Fructose Galactose	Sucrose Lactose Maltose	Plants: -       Starch -       Fiber Animals: -       Glycogen

 

Glucose:

Known also as dextrose, blood sugar, or grape sugar, glucose is the usual mechanism for transport of carbohydrates in the body. It can be naturally found in foods, especially grapes. Glucose can come from breakdown of disaccharides or starch. A small amount is made from amino acids, lactate, pyruvate and glycerol in the liver through a process called gluconeogenesis.

What happens to glucose after absorption? 

1. Is carried in the blood as blood sugar to be used as an energy source for the cells. All cells and tissues in the body need insulin to consume glucose, except nervous tissue, red blood cells, kidney tubules, intestinal cells, and beta cells of the pancreas.
2. Forms glycogen through a process called glycogenesis, and then is stored in the liver and muscles.
3. Converts to fat to be stored for later use as energy.

Fructose:

Known also as fruit sugar, and levulose, fructose is found in fruits and honey. It is the sweetest sugar, and after absorbing into the blood stream, it converts into glucose in the liver.

Galactose:

Galactose cannot be found in nature. It comes from the breakdown of lactose (milk sugar) and is converted into glucose in the liver.

Sucrose:

Sucrose is a disaccharide made of one molecule of glucose and one molecule of fructose. It is the most common disaccharide in diet and can be found in sugar cane, beets, maple syrup, molasses, honey, and pineapple.

It also called white sugar, brown sugar, table sugar, beet sugar, and cane sugar.

Maltose:

Maltose is a disaccharide composed of two units of glucose. It is found in beer, breakfast cereals, malted snacks, and germinating seeds such as barley.

Lactose:

It is a disaccharide made of one unit glucose and one unit galactose. Lactose is found only in milk (milk sugar). Among disaccharides, it is the least sweet one and is never found in plants. Lactose is broken down by the enzyme lactase into glucose and galactose.

Starch: 

Starch is a polysaccharide and is the stored form of carbohydrates in plants. It is found in rice, bread, grains, corn, potatoes, arrowroot, buckwheat, millet, oats, rye, yams, noodle, pasta, cassava, quinoa, and legumes. The starch in plants is also called complex carbohydrates. There are two forms of starch: amylopectin, and amylose.

Amylopectin:

1. Is made of short and branched chains of glucose molecules.
2. Is the most common starch in foods.
3. Foods high in amylopectin digest and absorb rapidly.

Amylose:

1. Is made of long and linear chains of glucose molecules.
2. Is the least common starch.
3. Foods high in amylose digest slowly.

For the amounts of carbohydrates in grains, refer to the following table.

 

Grains:
Grains	Serving Size	Carbohydrate (grams)	Fiber (grams)
Amaranth	1 cup, uncooked	128	13
Barley	1 cup, cooked	44	6
Buckwheat	1 cup, uncooked	122	18
Bulgur	1 cup, cooked	35	8
Corn (maize)	1 ear, medium	17	2.5
Fonio	1 cup, cooked	41	2.3
Kamut	1 cup, cooked	52	7
Millet	1 cup, cooked	42	2
Oats	1 cup	104	16
Quinoa	1 cup, cooked	40	5
Rice, brown	1 cup, cooked	45	5
Rice, white	1 cup, cooked	45	1
Rice, wild	1 cup, cooked	35	3
Rye	1 cup	120	25
Semolina	1 cup	122	8
Sorghum	1 cup	144	12
Spelt	1 cup, cooked	50	8
Teff	1 cup, cooked	50	5
Triticale	1 cup, uncooked	140	22
Wheat	1 cup, uncooked	140	24
Grains – Related Foods:
Bagel, regular	1	30	2
Bagel, whole wheat	1	30	4
Bread, oatmeal	1 slice	13	1
Bread, pita, white	1 slice	13	0.5
Bread, raisin	1 slice	16	1
Bread, rye	1 slice	15	3
Bread, wheat	1 slice	13	1
Bread, whole wheat	1 slice	13	3
Noodles	1 cup, cooked	37	2
Pasta	1 cup, cooked	37	2
Pasta, whole wheat	1 cup, cooked	38	4
Roll, French	1	19	1
Roll, hamburger bun	1	21	1
Roll, hotdog bun	1	21	1
Roll, pumpernickel	1	19	2
Tortilla	1	15	1
Waffle	1, 7” diameter	27	2

Complex Carbohydrates:
Without Gluten	With Gluten
Amaranth Arrowroot Buckwheat Corn Millet Potatoes Quinoa Rice Teff Yams	Barley Bulgur Couscous Kamut Muesli Oats Rye Semolina Spelt Triticale Wheat

 

Glycogen:

Glycogen is the stored form of carbohydrates in humans and animals. It is a polysaccharide made of subunits of glucose through a process called “glycogenesis” in the liver. Glycogen is stored in the liver and muscles. An average person has about 350 grams of glycogen in the muscles and about 50 grams in the liver.

The body has an upper limit for storing glycogen. It is 15 grams per kilogram of body weight, of which about 80% is stored in the muscles and 20% in the liver.

Contents of Carbohydrates in Fruits and Vegetables:

For the amounts of carbohydrates in fruits and vegetables, you may click on the following links:

Contents of Carbohydrates in Fruits:

Contents of Carbohydrates in Vegetables:

Fiber and Glycemic Index (GI):

For detailed information about fiber and glycemic Index, you may click on the following links:

Fiber:

Glycemic Index (GI):