Nutrition ch 4: the carbohydrates: sugars, starches and fibers

Digestion and absorption carbohydrates: small intestine

- Pancreatic amylase - specific disaccharide enzymes: maltase, sucrase, and lactase starch: the pancreas produces an amylase that is released through the pancreatic duct into the small intestine, then disaccharide enzymes on the surface of the small intestine cells hydrolyze the diasccharides into monosaccharides. Fiber: fiber is not digested and it delays absorption of other nutrients.

Making glucose from protein

- amino acid conversion - gluconeogenesis.

Dental caries

- bacteria ferment sugars producing acid. - food factors associated with tooth decay: time of food in mouth, sticky foods and frequency of sugar consumption. - food choices - factors associated with tooth decay.

Balancing within the normal range

- balance meals at regular intervals. diabetes: insulin is either inadequate or ineffective.

Health effects and recommended intakes of sugar continued

- dietary guidelines: choose and prepare foods with little added sugar. - DRI: added sugars; less than 25% of day's total energy - WHO and FAO recommendation: less than 10% of total energy - Artificial sweeteners: non-nutritive sweeteners and large doses and adverse effects. Stevia: an herbal product; generally recognized as safe. sugar alcohols: provide kcalories, benefits and side effects

Health effects and recommended intakes of starch and fibers continued

- excessive fiber: insufficient energy or nutrient needs, abdominal discomfort, gas, diarrhea, GI obstruction, nutrient absorption, dietary goals: balance, moderation and variety. - DRI for carbohydrates: 45 to 65% of energy requirement - RDA for carbohydrates: 130 grams per day - fiber: DV; 25 grams for a 2000 kcalorie diet. DRI; 25-35 grams per day. No upper limit

Glucose for energy

- fuels most of the body's cells: preferred source for brain, nerve cells and developing red blood cells. - cellular break down of glucose.

Health effects and recommended intakes of starch and fibers

- heart disease: whole grains; what are good sources. soluble fibers: oat bran, barley, legumes. Have cholesterol-lowering effect. - diabetes: high-fiber foods. - GI health: high-fiber foods and ample fluids - Cancer: dietary fiber and colon cancer: fiber supplements. Sources of dietary fiber: phytochemicals. preventing colon cancer: diluting, binding and removing, stimulate bacterial fermentation. - Weight management: high-fiber foods and whole grains- feeling of fullness.

Lactose intolerance: lactose activity

- highest immediately after birth - declines with age - prevalence: genetically determined. - dietary changes: manage dairy consumption rather than restriction (GI bacteria), fermented milk products, individualized diets, many result in nutrient deficiencies (riboflavin, vitamin D, and calcium

Ketone bodies from fat fragments

- inadequate supply of carbohydrates: - fat metabolism will shift - starvation: ketone bodies will form - then ketosis forms: acid-base balance - 50 - 100 grams of carbohydrates per day: needed for protein sparing and ketosis prevention - using glucose to make fat

The carbohydrate family

- monosaccharides: chemical shorthand. glucose, fructose and galactose. - Disaccharides: maltose, sucrose, and lactose - Polysaccharides: starches and fibers

Polysaccharides

- more complex - contain many glucose units - glycogen: storage form of energy in the body - starch: storage form of energy in plants - fibers: structural parts of plants, functional fibers, resistant fibers, phytic acid, insoluble fibers and pectin: soluble fibers

Absorption

- most nutrient absorption takes place in small intestine. - glucose and galactose are absorbed by active transport. - fructose are absorbed by facilitated diffusion.

Disaccharides

- pairs of three monosaccharides - maltose: two glucose units - sucrose: glucose and fructose - lactose: galactose and glucose - condensation: links two monosaccharides together. - hydrolysis: breaks a disaccharide into two.

Health effects and recommended intakes of sugar

- pleasure in moderate amounts - health effects of sugars: obesity and nutrient deficiencies - honey: same effects as refined sugar and more energy per spoonful.

Glycemic response

- speed of glucose absorption, how high it rises and the rate of return to normal levels.

Maintaing blood glucose homeostasis

1. when a person eats, blood glucose rises 2. high blood glucose stimulates the pancreas to release insulin into the bloodstream 3. insulin stimulates the uptake of glucose into cells and storage as glycogen in the liver and muscles. Insulin also stimulates the conversion of excess glucose into fat for storage. 4. As the body's cells use glucose, blood levels decline. 5. Low blood glucose stimulates the pancreas to release glucagon into the bloodstream. 6. Glucagon stimulates liver cells to break down glycogen and release glucose into the bloodstream. 7. Blood glucose begin to rise.

Glucose in the body

Carbohydrate role: supplies glucose. Storing glucose as glycogen. - liver storage: condensation into glycogen and hydrolysis for release of glucose when needed. - muscle storage: selfishly hoards glycogen

Monosaccharides

Most important in nutrition - same number and kinds of atoms - differing in sweetness - glucose: blood sugar. part of every disaccharides. - fructose: sweetest of the sugars - galactose: occurs naturally in very small amounts.

Digestion and absorption carbohydrates: mouth

amylase starch: The salivary glans secrete saliva into the mouth to moisten the food. fiber: the mechanical action of the mouth crushes and tears fiber into food and mixes it with saliva to moisten it for swallowing.

Liver

facilitates conversion of fructose and galactose.

Digestion and absorption carbohydrates: large intestine

fibers most fiber passes intact through the digestive tract to the large intestine. here, bacterial enzymes digest fiber. Fiber holds waterr, regulates bowel activity, and binds substances such as bile, cholesterol and some minerals, carrying them out of the body.

Digestion and absorption carbohydrates: ultimate goal

glucose for absorption and use hydrolysis via enzymes.

Blood glucose homeostasis

insulin: moves glucose from blood into the cells. glucagon and epinephrine: brings glucose out from storage.

The constancy of blood glucose

steady supply in bloodstream: intestine- food and liver- glycogen

Digestion and absorption carbohydrates: stomach

stomach acid and protein-digesting enzymes role of fiber starch: stomach acid inactivates salivary enzymes, halting starch digestion. Fiber: fiber is not digested, and it delays absorption of other nutrients.

muscles

use glucose, glycogen and fat.

Brain

uses glucose