Carbohydrates are the body's preferred energy source for most functions. They are recognized as the fuel of choice. The brain depends on them and will use approximately 125 grams of carbohydrates per day.
All plant sources contain mostly carbohydrates and the only negligible animal source is milk. We acquire glucose from all plant foods. Think "from the sun".
Three types of Carbohydrates
Simple: (Stored as glycogen in the liver and muscle tissue)
Monosaccharide – single sugar – glucose, fructose, galactose (part of lactose)
Fiber: Non-digestible cellulose that sweeps the body's intestines and promotes colon and heart health.
See my section on soluble and insoluble fiber.
Total intake should be 45-60% of total calories. Sweets (added sugars) should be limited to fewer than 10% of total calorie intake. This is called discretionary calories. Sugars in milk and fruit are accompanied by many other nutrients and should be consumed even if following a low carbohydrate diet.
Choose whole grain products, starches, vegetables and fruits for most of your total carbohydrate intake.
2000 calories per day = 225 grams-300grams per day (remember the brain needs 125 grams)
Foods that average 15 grams of carbohydrates
1 slice bread, ¼ of a regular size bagel
½ cup cooked cereal
1/3 cup cooked rice, grain or starchy vegetable
6 saltine crackers
1 small fresh fruit
½ cup canned fruit
¼ cup dried fruit
If a diet is too low in carbohydrates the body will break down protein (strips off and excretes the nitrogen from the amino acids) to generate the glucose it needs.