Chapter 4Carbohydrates: Sugar, Starches and Fiber

Carbohydrates in Our Diet

Carbohydrates make up most of the energy in a healthy diet.

Grains are sources of carbohydrates. Refined carbohydrates lack fiber and many

rich nutrients. Unrefined carbohydrates are healthier to eat.

Unrefined and Refined Foods

Whole Grains

Whole grains are made up of bran: containing fiber and vitamins

germ: mainly protein and vitamins

endosperm: starch, protein, vitamins, and minerals

Empty CaloriesMany processed/ready to eat foods contain added sugar that reduces nutrient density (empty calories)

Types of Carbohydrates Glucose, fructose and galactose are simple

carbohydrates. Glucose is the blood sugar and found in cells. Sucrose is made up of a molecules of

glucose and a molecule of fructose is a disaccharide.

Maltose is made up of two glucose molecules.

Lactose contains one glucose and one galactose.

Monosaccharides

Dissaccharides

Simple carbohydrates have one or two molecules of single sugars. maltose, sucrose and lactose are simple

carbohydrates. Glucose, galactose and fructose are single

carbohydrates. Glucose is the blood sugar and source of energy

from carbohydrates. Galactose is milk sugar important in producing

milk in lactating women and animals.

Dissaccharides

Complex Carbohydrates

Complex carbohydrates contain many molecules of glucose.

Starch, glycogen and cellulose are complex carbohydrates. Starch and glycogen are synthesized by a chain

of glucose molecules joined by alpha 1–4 and 1–6 bonds they also have branched chain attached.

Fiber (cellulose) is a chain of glucose molecules joined by beta 1–4 bond that human intestine does not produce the enzyme to digest it.

Complex Carbohydrates

Glucose is Produced by Plants through Photosynthesis

Chemistry of Carbohydrates

Starch is stored in the grains, stems and root of the plant.

Fiber is found in the bran of the grains, stem, leaf, and other structures of the plants.

There are two types of fiber in the plant varieties: Soluble fiber in fruits, oats and legumes Insoluble fiber mostly in grains and vegetables

Soluble and Insoluble Fiber

Pectin Beans

Fiber

Humans do not produce enzyme to digest fiber—therefore, no calories from fiber.

Fiber provides many health benefits to humans: Insoluble fiber:

provides bulk in the intestine to ease elimination. prevents constipation, diverticulitis, appendicitis, and

may prevent colon cancer. Soluble fiber:

combines with bile, eliminate it, preventing elevated blood cholesterol

Carbohydrate Digestion & Absorption Mouth Small intestine

Digestive enzymes from pancreas Absorption through the small intestinal villi

Active absorption Passive diffusion

Large intestine Elimination of undigested starch and fiber Modification of intestinal microflora Role of the pancreas

Carbohydrate Digestion

Glycemic Index

Different carbohydrate containing foods are absorbed at different rate.

Simple carbohydrates and potato starch are absorbed fast and make a large spike in the blood sugar (a high glycemic index) causing a high insulin response.

Beans, legumes and some mixed foods are absorbed slower and have lower glycemic index.

Glycemic Index

Carbohydrate Functions

Getting glucose to the cells, role of insulin. Problems of glucose metabolism

Type 1 diabetes, pancreases loss of insulin producing ability. Autoimmune problem

Type 2 diabetes increased body fat cells causing resistance to insulin

delivery of glucose to the cells Role of insulin in regulating blood glucose levels

Functions of Monosaccharide

Absorbed monosaccharids enter liver where galactose and fructose are converted to glucose.

Glucose enters the blood and circulates. Insulin helps glucose enter the cells for energy. Glucagon helps excess blood glucose return to

liver and muscles to form storage and form glycogen

Glucose also is a part of genetic DNA, RNA, ATP and other functional molecules in the body.

Blood Glucose Regulation

Cellular Carbohydrate Metabolism In cells, glucose is metabolized to produce

energy. There are two pathways for producing energy:

Anaerobic pathway (incomplete metabolism) with production of lactate. Happens in absence of oxygen. Resulting in lower energy

production Aerobic pathway (complete metabolism) with end

products of CO2 and H2O. Happens when oxygen is present. Produces lot more energy.

Cellular Respiration

Breakdown of Fat and Protein In the absence of carbohydrates body breaks down

protein to form glucose to feed the brain. About ½ of amino acids skeletons can produce glucose Other amino acids produce ketone

acidic molecules that changes the pH of body environment to acid.

Body also breaks down the stored fat to provide energy for body needs Fat breakdown in the absence of carbohydrates results in

ketone production. Ketone bodies are harmful to the body and are excreted

through the urine. Severe ketosis can occur with untreated diabetes and can

cause coma and even death.

Ketone Formation

Carbohydrates and Health

Are carbohydrates good or bad for you? What kind of carbohydrates are beneficial to

health? Whole grains, complex carbohydrates foods are healthy

carbohydrates. What kind are not healthy carbohydrates to

consume? Refined carbohydrates and food with added sugar are

not healthy and may cause risk of chronic diseases.

Diabetes

Carbohydrates are generally blamed for diabetes. The interesting fact is again which kind of carbohydrates are to be blamed. Whole grain and complex carbohydrates prevent

type 2 diabetes by preventing fat cells accumulation in the body.

Refined carbohydrates increase empty calories in the diet may cause weight gain, increase resistance to insulin causing type 2 diabetes.

Diabetes

Type 1 diabetes is due to lack of production of insulin from pancreas causing blood glucose to elevate.

It can be controlled by a diet very low on fast absorbing starches (potato) and refined sugars. A diet high in fiber and whole grains help slow

absorption and prevent fast rise in blood sugar. In sever cases insulin must be injected to regulate

blood sugar levels.

Blood Glucose Levels in Diabetes

Diabetes

Incidences of diabetes in the US is on the rise. Certain racial groups are more susptible to

diabetes than others. Lifestyle, dietary habits physical activity and

environment also play a role. Managing diabetes with diet, exercise and

medication. Symptoms and complications of diabetes.

Incidence of Diabetes

Other Health Problems

Hypoglycemia: Reactive hypoglycemia Fasting hypoglycemia

Dental caries: Dental hygiene Refined sugars

Carbohydrates and weight management: Which kind to consume?

Carbohydrates and Weight Management

Carbohydrates & Body Weight Carbohydrates and weight management. Role of refined carbohydrates in storage of fat. Role of insulin in body fat accumulation. The consequence of low or no carbohydrate

diets? Ketosis and ketogenic diets

Role of ketones in weight loss Benefits and harms of nonnutritive sweeteners.

Nonnutritive Sweeteners

Carbohydrates and Heart Disease Diets with high sugar, added sugar

glucose or any simple sugar raise blood sugar, cholesterol and the risk of heart disease.

High fiber containing diets with both soluble and insoluble fiber reduce the risk of heart disease.

Carbohydrates and Heart Disease Consuming foods high in soluble fiber reduce

cholesterol synthesis by liver. Soluble fiber in legumes, fruits, oats, brown

rice, etc. bind with bile in the intestine, removing it from the body preventing bile reabsorption, and cholesterol re-synthesis.

Soluble fiber may also reduce blood cholesterol by other means.

Cholesterol and Soluble Fiber

Carbohydrates and Heart Disease Diets with high insoluble help reduce risk of

heart disease by: Reducing absorption of starch and sugars. Keeping blood glucose normal Reducing food intake by filling the stomach and

reducing the appetite. Preventing obesity Reducing blood pressure. Preventing formation of diverticula

Diverticula

Intestinal Health and Fiber Insoluble fiber is not digested, absorbs water

in the intestine and increase in volume conferring benefits: Softens the stool, making elimination easy. Preventing constipation, diverticulitis, appendicitis,

hemorrhoids, and possibly colon cancer. Speed up the movement of waste materials from

the bowl. Modify the bowl micro flora environment positively.

Meeting Carbohydrate Needs

Carbohydrates intake is to meet the needs of: Adequate blood glucose levels to meet the brain, red

blood cells and nerves energy requirements (about 300 grams/day).

Minimum carbohydrate intake to prevent ketosis is 100 grams/day

Recommendations are: 45% – 65% of total daily calorie intake should come

from complex carbohydrates. In the US diet, the right percentage of calories

consumed from carbohydrates, but it is mostly refined or added sugars.

Healthy Carbohydrate Choices

Choosing Carbohydrates Wisely

End of Chapter 4

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