MACRONUTRIENTS

 WHAT ARE MACRONUTRIENTS?

Macronutrients are nutrients that provide calories/energy. 

Since “macro” means large, they are nutrients needed in large amounts. 

There are three macronutrients:

• Carbohydrate 

• Protein 

• Fat 

Macronutrients contribute to the energy pool of the body.

While each of these macronutrients provides calories, the amount of calories that each one provides varies.

• Carbohydrate provides 4 K/calories per gram.

• Protein provides 4 K/calories per gram.

• Fat provides 9 K/calories per gram.

Besides carbohydrate, protein, and fat the only other substance that provides calories is alcohol.

Alcohol provides 7K/calories per gram. 

Alcohol, however, is not a macronutrient because we do not need it for survival.

WHY DO WE NEED CARBOHYDRATES TO SURVIVE?

We need carbohydrate because:

• 45% - 65% of calories should come from carbohydrate 

• Carbohydrates are the body’s main source of fuel. 

•  All of the tissues and cells in our body can use glucose for energy. 

• Carbohydrates are needed for the central nervous system, the kidneys, the brain, the muscles (including the heart) to function properly. 

•  Carbohydrates can be stored in the muscles and liver and later used for energy(glycogen). 

•  Carbohydrates are important in intestinal health and waste elimination (e.g.. Dietary fiber). 

Dietary fiber

• Fiber refers to certain types of carbohydrates that our body cannot digest (oligosaccharides and non-starch polysaccharides). 

• These carbohydrates pass through the intestinal tract intact and help to move waste out of the body. 

• Diets that are low in fiber have been shown to cause problems such as constipation and hemorrhoids and to increase the risk for certain types of cancers such as colon cancer. 

• Diets high in fiber; however, have been shown to decrease risks for heart disease, obesity, and they help lower cholesterol. 

• Foods high in fiber include fruits, vegetables, and whole grain products. 

Dietary Fiber prevents Constipation, Hemorrhoids & Diversticulosis by:

 

• Increasing perystalsis making stool bulk

• Decreasing intestinal transit time of contents

Food sources of Carbohydrates

• Free sugars are found from: fruits, juices, Soft drinks, milk, sugar, sugar cane, honey and yogurt, Cereal grains, Legumes & dried fruits, vegetables, processed foods (pasta), pastries, breads, candies , fruits like banana, dates, and sweet potato 

• Starch is found from: starchy foods (like cereals and legumes and potatoes), Other foods like fruits, vegetables, beans, nuts, seeds

 

• OligoSacharides are found from : Garlic, onion, Whole grain cereals and legumes

• Non starch polysaccharides are found from: Fruits, vegetables, Whole grain cereals and legumes

Carbohydrate digestion: Carbohydrates break down into glucose in order the body to absorb and use.

• Large starch molecules needs extensive breakdown. 

• Disaccharides - broken once

• Monosaccharide - don’t need to be broken down, 1-4 hours is needed for sugars and starches to be digested.

• Digetion of carbohydrate begins in mouth chewing releases saliva and enzyme amylase hydrolyzes starch to polysaccharides and maltose. 

• In the stomach no enzymes available to break down starch ,acid does some breakdown

• Small intestine -majority of carbohydrate digestion takes place here. Pancreatic amylase reduces carbohydrates to glucose chains or disaccharides and specific enzymes finish the job. 

• Maltase convertes maltose into 2 glucose, Sucrase changes sucrose into glucose and fructose and Lactase changes lactose into glucose and galactose.

• large intestine only fibers remain, attract water, which softens stool, bacteria ferment some fibers water, gas, short-chain fatty acids (used for energy)

Carbohydrate absorption: Glucose absorption can be started in the mouth where majority absorbed in small intestine. 

     Insulin 

•   The secretion is stimulated by Hyperglycemia and Parasympathetic nervous activity 

 

    Glucagon

• The secretion is stimulated by Hypoglycemia and Sympathetic nervous activity 

Requirements

• The RDA for carbohydrate is set at 130 g/day

 

• Minimum of 50 – 100 grams of carbohydrates/day are needed to avoid ketosis.

• Adults should consume 45–65 percent of their total calories from carbohydrates. 

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