What are Carbohydrates

What are Carbohydrates?

Definition of Carbohydrate:
: any of various neutral compounds of carbon, hydrogen, and oxygen (as sugars, starches, and celluloses) most of which are formed by green plants and which constitute a major class of animal foods
References:
http://www.merriam-webster.com/dictionary/carbohydrate
RDA of Carbohydrate:
The 10th edition of the RDA discusses carbohydrates in the context of dietary fiber and digestible carbohydrates, which provide energy, and recommends that more than half the energy requirement beyond infancy be provided by carbohydrates and that a desirable intake of fiber be achieved by consumption of fruits, vegetables, legumes, and whole-grain cereals. The recommendations on digestible carbohydrates are primarily based on the desirability of limiting the intake of fat. An additional consideration is the suggestion that excess calories from carbohydrate vs. fat are metabolized and stored with different efficiencies. The scientific basis for recommending an appropriate intake of dietary fiber is not clearly evident in the current RDA. The association between a high plant food, and thus fiber intake, and lower incidence of cardiovascular disease, colon cancer, and diabetes is of interest but difficult to use to form the basis of specific recommendations for an appropriate amount of fiber to include in the diet. The importance of fiber for normal gastrointestinal function provides the best scientific basis for developing recommended intake levels. Dietary fiber, as well as non-digested starch, are the only known dietary components that increase stool weight and are the primary substrates for the microflora in the large intestine. Metabolism of this microflora, including production of short chain fatty acids that are used by epithelial cells, appears to be important for intestinal health. However, the challenge we still face is to define the parameters of gastrointestinal function that are compatible with health.
References:
Department of Nutrition, University of California, Davis, CA 95616
http://jn.nutrition.org/cgi/content/abstract/124/9_Suppl/1747S
The RDA was developed during World War II by Lydia J. Roberts, Hazel Stiebeling and Helen S. Mitchell, all part of a committee established by the U.S. National Academy of Sciences in order to investigate issues of nutrition that might "affect national defense" (Nestle, 35). The committee was renamed the Food and Nutrition Board in 1941, after which they began to deliberate on a set of recommendations of a standard daily allowance for each type of nutrient. The standards would be used for nutrition recommendations for the armed forces, for civilians, and for overseas population who might need food relief. Roberts, Stiebeling, and Mitchell surveyed all available data, created a tentative set of allowances for "energy and eight nutrients", and submitted them to experts for review (Nestle, 35). The final set of guidelines, called RDAs for Recommended Dietary Allowances, were accepted in 1941. The allowances were meant to provide superior nutrition for civilians and military personnel, so they included a "margin of safety." Because of food rationing during the war, the food guides created by government agencies to direct citizens' nutritional intake also took food availability into account.
The Food and Nutrition Board subsequently revised the RDAs every five to ten years. In the early 1950s, USDA nutritionists made a new set of guidelines that also included the number of servings of each food group in order to make it easier for people to receive their RDAs of each nutrient.
In 1997 at the suggestion of the Institute of Medicine of the National Academy RDA became one part of a broader set of dietary guidelines called the Dietary Reference Intake used by both the United States and Canada.
References:
Nestle, Marion. Food Politics. Berkeley: University of California Press, 2002. ISBN 9790520224659.
The FDA uses Daily Values (DVs) for food labeling. DVs for the following macronutrients are Daily Reference Values (DRVs).[1][2] The DV's used by the FDA for vitamins and minerals are the RDIs listed here.
For people 4 years or older, eating 2,000 calories per day, the RDIs are:
Total Fat
65 g

Saturated Fatty Acids
20 g
Cholesterol
300 mg

Sodium
2400 mg
Potassium
4700 mg
Total Carbohydrate
300 g
Fiber
25 g
Protein
50 g

For vitamins and minerals, the RDIs are given in the following table, along with the more recent RDAs of the Dietary Reference Intakes (maximized over sex and age groups):[2]
Nutrient RDI highest RDA of DRI

Vitamin A
3000 IU
10,000 IU
Vitamin C
60 mg
90 mg
Calcium
1000 mg 1300 mg
Iron
18 mg 18 mg
Vitamin D
400 IU 600 IU
Vitamin E
30 IU 15 mg (33 IU of synthetic)
Vitamin K
80 μg
120 μg
Thiamin
1.5 mg 1.2 mg
Riboflavin
1.7 mg 1.3 mg
Niacin
20 mg 16 mg
Vitamin B6
2 mg 1.7 mg
Folate
400 μg 400 μg
Vitamin B12
6 μg 2.4 μg
Biotin
300 μg 30 μg
Pantothenic acid
10 mg 5 mg
Phosphorus
1000 mg 1250 mg
Iodine
150 μg 150 μg
Magnesium
400 mg 420 mg
Zinc
15 mg 11 mg
Selenium
70 μg 55 μg
Copper
2 mg 900 μg
Manganese
2 mg 2.3 mg
Chromium
120 μg 35 μg
Molybdenum
75 μg 45 μg
Chloride
3400 mg 2300 mg
References:
^ http://www.fda.gov/FDAC/special/foodlabel/dvs.html
1. ^ http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=8c5344f04a8ae103e5b0ff5a17c7fa97&rgn=div8&view=text&node=21:2.0.1.1.2.4.1.1&idno=21