Dietary Carbohydrate

Primary role of dietary Carbohydrates: %%provide energy%%

Classification

Principal monosaccharides found in food:

corn syrup that has undergone enzymatic processing to convert their glucose into fructose and have been mixed with pure corn syrup (100% glucose) to produce a desired sweetness
HFCS 55 (55% fructose and 42% glucose): substitute for sucrose on %%beverages%% (e.g. soft drinks)
HFCS 42 used in %%processed foods%%
composition of HFCS and surcose are similar
- major difference: HFCS is ingested as a mixture of monosaccharides
- ^^no significant difference^^ in either ^^postprandial glucose or insulin responses^^

Most abundant:

sucrose: @@table sugar@@
- glucose + fructose
lactose: principal sugar found in @@milk@@
- glucose + galactose
maltose: product of enzymatic digestion of polysaccharides, found in @@beer and malt liquors@@
- glucose + glucose

complex carbohydrates
most often polymers of glucose
do not have a sweet taste
^^Sources^^: starch, wheat, potatoes, dried peas, beans (legumes) and vegetables

Dietary fiber: non-digestible, non-starch carbohydrates and lignin present in plants

@@soluble fiber@@ is the edible part of plants
- @@resistant to digestion and absorption@@ in the human small intestine
@@insoluble fiber@@ passes through the digestive track largely @@unchanged@@
provides little energy
Recommended intake (AI) for total fiber:
- ==25 g/day for women==
- ==38 g/day for men==

}}Type of Fiber}}	}}Major Source in Diet}}	}}Chemical Properties}}	}}Physiological Effects}}
Cellulose	Unrefined cereals, bran, whole wheat	Nondigestible, water insoluble, absorbs water	Stool bulk, intestinal transit time, intracolonic pressure
Hemicellulose	Unrefined cereals, some fruits and vegetables, whole wheat	Partially digestible, usually water insoluble, absorbs water	Stool bulk, intestinal transit time, intracolonic pressure
Lignin	Woody part of vegetables	Nondigestible, water insoluble, absorbs organic substances	Stool bulk, binds cholesterol, binds carcinogens
Pectin	Fruits	Digestible, water soluble, mucilaginous	Rate of gastric emptying,Rate of sugar uptake, Serum cholesterol
Gums	Dried beans, oats	Digestible,water soluble, mucilaginous	Serum cholesterol, Rate of gastric emptying,Rate of sugar uptake

adds bulk to diet
increasing bowel mobility during exposure of intestines to carcinogens
promoting bowel movements (laxation)
softens stool: decrease risk for constipation, hemorrhoids, and diverticulosis
soluble fiber:
- delays gastric emptying
- which can result in a sensation of fullness (satiety)
- reduce spikes in blood glucose following a meal
- lower plasma LDL-C levels by @@increasing fecal bile acid excretion@@ and @@interfering with bile acid reabsorption@@

carbohydrates differ in their glycemic response (GR)
- carbohydrate-containing foods produce either
- rapid rise followed by a steep fall in blood glucose
- gradual rise followed by a slow decline in blood glucose
Glycemic index (GI): the area under the blood glucose curve seen after ingestion of meal with carbohydrate-rich food, compared with the area under the blood glucose curve observed after a meal consisting of the same amount of carbohydrate in the form of glucose or white bread.
^^low GI:^^ <50
^^high GI:^^ ≥70
low-GI diet improves glycemic control in diabetic individuals
foods with low GI tend to create a sense of satiety over a long period of time
- helpful in limiting caloric intake