Chapter 5 Carbohydrates The Preferred Body Fuel Carbohydrates

Chapter 5 Carbohydrates: The Preferred Body Fuel

Carbohydrates l Essential nutrient l Body’s main source of energy l Sugar, Starches, Fiber l Nearly all sources are plant sources l Carbon, hydrogen and oxygen bonded to form saccharides

TYPES OF CARBOHYDRATES Monosaccharides, Disaccharides and Polysaccharides Monosaccharides – composed of single sugar units l - the smallest carbohydrate molecule

MONOSACCHARIDES l 1. Glucose - blood sugar l - Circulates in the bloodstream l - the body’s source of energy l

MONOSACCARIDES l 2. Fructose - sweetest tasting of the sugars l - occurs naturally in fruits and honey l

MONOSACCHARIDES l 3. Galactose - doesn’t occur alone l - bonded to glucose to form lactose; milk sugar l

DISACCHARIDES l -Made up of two sugar units; must be split during digestion to form monosaccharides l 1. l Sucrose – sugar as additives (1 glucose+ 1 fructose) Ex. Beet sugar, sugar cane, molasses, maple syrup

DISACCHARIDES l 2. l Lactose – milk sugar (1 glucose + 1 galactose bonded together) 3. Maltose – (2 glucose, bonded together) - formed during digestion of starch; -found in some grains such as malt

POLYSACCHARIDES l- Carbohydrates made up of many sugar units that must be broken down during digestion; starches and fiber

POLYSACCHARIDES 1. Starches – the storage form of energy in plants l - many glucose molecules bonded together l - grain products l

POLYSACCHARIDES l 2. Dietary Fiber -tough fibrous cell walls of plants l - found only in plant foods l - enzymes can’t digest fiber but bacteria in the digestive track can break down some fiber l - little to no energy (calories) provided by fiber l

l SIMPLE l CARBOHYDRATES - Mono and Disaccharides (sugars) COMPLEX CARBOHYDRATES - Polysaccharides due to complex molecular structure (starches and fiber)

FUNCTIONS OF CARBS l 1. Provide Energy – preferred source because the body can use them most efficiently l 2. Spare Proteins – protein is used for energy when carbs are unavailable but used less efficiently; proteins primary function is to build and maintain cells

FUNCTIONS OF CARBS l 3. Break Down Fats – body can’t completely break down fats if diet is too low in carbs - ketone bodies blood may become too acidic ketosis (damages cells and organs, nausea, weakness) coma and death

FUNCTIONS OF CARBS l 4. Provides Bulk in the Diet – promotes normal digestion and elimination of wastes l -feel full sooner l -slower to leave the stomach so feel full longer l -usually lower in calories

FUNCTION OF CARBS l Dietary Fiber - Soluble Fiber – can dissolve in water and develops a gel-like consistency; ex. Oat bran, legumes, apple and citrus pectin l - Insoluble Fiber – does not dissolve in water; associated with reducing cancer risks; ex. wheat bran, whole grain Functional Fiber – taken from plants, developed in labs- added to processed foods to provide health benefits l

How Your Body Uses Carbs l - Carbs must be converted to glucose for cells to use them as energy source l - Poly’s and Di’s are broken down into Mono’s which are small enough to move through the intestinal wall into the bloodstream

Using Carbs l Mono’s travel to the liver where fructose and galactose are converted into glucose

Using Carbs l Blood sugars rise hormone called insulin is released to help lower glucose levels by burning glucose for energy l Hormone – chemicals produced in the body and released into the blood stream to regulate specific body processes

Using Carbs l If there is no immediate energy needs the glucose is stored as glycogen; l 2/3 of glycogen is stored in the muscles, 1/3 stored in the liver l -the liver can store limited amount; excess is stored as fat l -fat stores cannot be converted back to glucose