Chapter 4 - Carbohydrates

What Are Carbohydrates?

Carbohydrates

• One of the three macronutrients

• An important energy source, especially for

nerve cells

• Composed of the atoms carbon, hydrogen,

and oxygen

• Good sources include fruits, vegetables, and

grains

What Are Carbohydrates?

Glucose

• The most abundant carbohydrate

• Produced by plants through photosynthesis

• The preferred source of energy for the brain

• An important source of energy for all cells

Photosynthesis

What Are Simple Carbohydrates?

Simple carbohydrates contain one or two sugar

molecules.

• Monosaccharides are the simplest carbs,

consisting of only one sugar.

• Glucose, fructose, galactose, ribose

• Disaccharides contain two sugar molecules.

• Lactose, maltose, sucrose

Monosaccharides

Disaccharides

Complex Carbohydrates

Complex Carbohydrates (polysaccharides) are

nutrients that consist of long chains of glucose

molecules.

• Starch

• Glycogen

• Fiber

Complex Carbohydrates

Starch

• A polysaccharide

stored in plants

• The two from of starch:

amylose and

amylopectin

• We digest (break down)

starch into glucose

• Grains and legumes are good sources of

dietary starch

Complex Carbohydrates

Glycogen

• A polysaccharide that is the storage form

of glucose in animals

• Stored in our bodies in the liver and muscles

• Not found in food and therefore not a dietary

source of carbohydrate

Complex Carbohydrates

Fiber

• Dietary fiber: the nondigestible part of plants

that form the support structures of leaves,

stems, and seeds.

• Cellulose, pectin, psyllium

Cellulose (fiber)

Six Benefits of Dietary Fiber

• Reduce risk of colon cancer

• Promotes bowel health (regularity)

• Reduce risk of diverticulosis (the condition of

having out-pocketings in the colon wall)

• Reduce risk of heart disease

• May enhance weight loss

• Reduce risk of Type II diabetes

Diverticulosis

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Complex Carbohydrates Summary

Why Do We Need Carbohydrates?

Energy

• Fuel daily activity

• Fuel exercise

• Help preserve protein for other uses

• When diet does not provide enough carbohydrate,

the process of gluconeogenesis converts proteins

in blood and tissue into glucose

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Carbohydrate Use by Exercise Intensity

Why Do We Need Carbohydrates?

Energy

• Each gram of carbohydrate = 4 kcal

• Red blood cells rely only on glucose for their

energy supply

• Both carbohydrates and fats supply energy

for daily activities

• Glucose is especially important for energy

during exercise

Very Low Carbohydrate Intake

Energy

• Insufficient energy intake from carbs causes

ketosis to occur

• Ketosis is the process by which the

breakdown of fat during fasting results in the

production of ketones as an alternate energy

source

• Excessive ketones can result in high blood

acidity, which damages body tissues

Very Low Carbohydrate Intake

Energy

• If glycogen levels become too low, your body

will signal your muscles to release protein

from you tissues (which depletes lean

muscles)

• The proteins then can no longer be used to

make new cells, repair tissue damage,

support the immune system, etc.

• Consuming carbs will spare protein from

being released as an energy source

Loss of Function from Low Carb Intake

When protein is used for energy they lose some

key functions:

• Proteins cannot be used to make new cells

• Cannot repair tissue damage

• Cannot support the immune system as

effectively

• Cannot properly perform any of their others

functions (maintaining body temp, creation of

hormones, etc.)

Effects from a Low Carb Diet

Energy

• The body will use protein for energy, taking

amino acids from:

• Blood

• Muscles

• Heart

• Liver

• Kidneys

• Can cause irreversible damage to these

organs.

Regulation of Blood Glucose: Insulin

Insulin

• A hormone secreted by the pancreas

• Transported in our blood throughout the body

• Helps transport glucose from the blood into cells

• Stimulates the liver and muscles to take up

glucose and convert it to glycogen

Eating Food HIGH in Glucose

• The following table summarizes how the body

will respond to the consumption of a meal that is

high in glucose (like a bowl of pasta)

HIGH Blood

Sugar

Step 1 Step 2 Step 3

Name of action: Insulin

secretion

Cellular uptake Glucose storage

Brief

Description:

The pancreas

secretes

insulin

Insulin travels to

tissue and stimulates

glucose transporters,

allowing glucose to

enter cells

Insulin

stimulates

glucose storage.

Health and High Sugar Diets

• High sugar diets put people at much higher risk

of the following:

• Tooth decay

• Heart disease

• Diabetes

• Obesity

• Unhealthy blood lipid levels

Diabetes

• A chronic disease in which the body cannot

regulate glucose within normal limits.

• This metabolic disease is caused when the

body cannot produce any or enough insulin,

which causes elevated levels of glucose in the

blood.

Type 1 Diabetes

Type 1 diabetes

• Accounts for about 5% of all cases

• Body does not produce enough insulin, so

cells cannot absorb glucose

• Creates high blood sugar (glucose) levels

• Key warning sign is frequent urination

• May lead to ketosis, coma, death

• Most frequently diagnosed in adolescents

• Has a genetic link

• Requires insulin injections daily

Type 2 Diabetes

Type 2 diabetes

• Accounts for 90–95% of cases

• Body cells become insensitive or

unresponsive to insulin and so glucose

remains in the blood

• Develops progressively over time

• Obesity is most common trigger

• Eventually the pancreas may become unable

to produce any insulin

• Drugs are prescribed that improve cell

sensitivity to insulin

Regulation of Blood Glucose: Glucagon

Glucagon

• Another hormone secreted by the pancreas

• Stimulates the breakdown of glycogen to glucose

to make glucose available to cells

• Stimulates gluconeogenesis—the production of

"new" glucose from amino acids

Eating Food HIGH in Glucose

• The following table summarizes how the body

will respond a drop in glucose that would take

place after not eating carbs for a long period.

LOW Blood

Sugar

Step 1 Step 2 Step 3

Name of action: Glucagon

secretion

Glycogenolysis

(glycogen splitting)

Gluconeogenesis

(glucose making)

Brief

Description:

The pancreas

secretes

glucagon

Glucagon

stimulates liver to

convert glycogen

to glucose

Glucagon

stimulates liver to

breakdown protein

into amino acids

and then into

glucose

Regulation of Blood Glucose

Glycemic index: a measure of a food's ability to

raise blood glucose levels

How Much Carbohydrate Should We Eat?

The Recommended Dietary Allowance (RDA) for

carbohydrate is 130 g per day just to supply the

brain with glucose

• 45–65% of daily calorie intake should be in

the form of carbohydrates

• Focus on foods high in fiber and low in added

sugars

• 25 g/day for women

• 38 g/day for men

Heathy Carbs: Whole-grain Foods

Whole-grain foods are kernels that retain the

bran, endosperm, and germ.

• Bran – outer covering

• Endosperm –

midsection containing

carbohydrates and

protein

• Germ – base of kernel

containing fats

Heathy Carbs: Whole-grain Foods

Whole-grain foods are much healthier sources than

foods with added sugar.

• Grains

• Vegetables

• Fruits

• Nuts

• Legumes

Artificial Sweeteners

• These are food additives that provide a sweet

taste like that of sugar, while containing

significantly less kcal.

• Current research concludes that (if consumed in

moderation) artificial sweeteners are not

harmful.

Chapter 5 - Fats

What Are Fats?

Fats are one type of lipid

Lipids: diverse class of organic substances that

are insoluble in water

• Lipids (fats) do not dissolve in water

Note:

• Fats – solid at room temperature

• Oils – liquid at room temperature

Triglycerides

Most of the fat we eat is in the form of triglycerides.

Triglycerides are composed of

• Three fatty acid molecules

• Fatty acids: long chains of carbon atoms surrounded

by hydrogen atoms

• One glycerol molecule

• Glycerol: a three-carbon alcohol that is the backbone

of a triglyceride

Triglycerides

Triglycerides

Saturated fatty acids have hydrogen atoms surrounding

every carbon in the chain; they have no double bonds

Foods high in saturated fat: Coconut oil, palm oil,

butter, cream, whole milk, beef

Monounsaturated fatty acids lack hydrogen atoms in one

region; they have one double bond

Foods high in monounsaturated fat: Olive oil, canola

oil, cashew nuts

Polyunsaturated fatty acids lack hydrogen atoms in multiple

locations; they have two or more double bonds

Foods high in polyunsaturated fat:

Cotton seed, canola, corn, safflower

Saturated and Unsaturated Fatty Acids

Levels of Saturation Among Fatty Acids

Major Sources of Dietary Fat

Triglycerides

The shape of a triglyceride is determined by the

saturation of the carbon chains

Saturated fatty acids can pack tightly together and

are solid at room temperature

• For example, coconut oil, animal fats, butter,

and lard are high in saturated fatty acids

Triglycerides

Unsaturated fatty acids do not stack together well

and are liquid at room temperature

• Unsaturated fatty acids are the predominant

type in plants

• Two exceptions are coconut and palm kernel

oil

The hydrogen atoms at the unsaturated region can

be arranged in different positions

• Cis: same side of the carbon chain

• Trans: opposite sides of the carbon chain

Cis and Trans Polyunsaturated Fatty Acids

Triglycerides

The majority of trans fats get into our foods during

food processing (ex. frying).

Hydrogenation: the addition of hydrogen atoms to

unsaturated fatty acids

• Converts liquid fats (oils) into a semisolid

(spreadable) or solid form

• Used to create margarine from plant oil

• Often creates trans fatty acids

• Listed on food labels as partially hydrogenated oil

Triglycerides

Why are trans fats so harmful?

The enzymes in our bodies cannot effectively

break down these fats.

Watch: “The Deal with Fat”

Essential Fatty Acids

Essential fatty acids cannot be synthesized in the

body and must be obtained in the diet

• Omega-6: A fatty acid that has its double

bond six carbons from the end

• Found in vegetable and nut oils, such as sunflower

oil, safflower oil, corn, soy, and peanut oil

• Daily intake: 14 – 17g (men); 11 – 12g (women)

Essential Fatty Acids

• Omega-3: A fatty acid that has its double

bond three carbons from the end

• Found in dark-green leafy vegetables, flaxseeds

and flaxseed oil, soybeans, and soybean oil,

walnuts and walnut oil, and canola oil

• Daily intake: 1.6 g (men); 1.1 g (women)

Sterols

Sterols: lipids containing multiple rings of carbon

atoms

• Essential components of cell membranes and

many hormones

• Manufactured in our bodies and therefore not an

essential component of our diet

• Cholesterol is the major sterol found in the body

Dietary Cholesterol

Where is it found?

• Found in animal products such as butter, egg

yolks, whole milk, red meats, and poultry

Do we need to consume it?

• We do not need to consume cholesterol, as our

bodies will synthesize it

Why do we need it?

• Sex hormones, production of bile, adrenal

hormones, and production of vitamin D

Why Do We Need Fats?

Energy

• Fat is very energy dense, providing 9 kcal/g

• Much of the energy used during rest comes

from fat

• Fat is used for energy during exercise,

especially after glycogen is depleted

• Fat is also used for energy storage

Why Do We Need Fats?

Fat is essential to many body functions

• Cell membrane structure

• Nerve cell transmissions

• Protection of internal organs

• Insulation to retain body heat

Fat Is Used for Energy During Exercise

How Much Fat Should We Eat?

The Acceptable Macronutrient Distribution Range

(AMDR) for fat

• 20%–35% of calories should be from fat

Athletes and highly active people may need more

energy from carbohydrates and can reduce their

fat intake to 20–25% of total calories

Recognize the Fat in Foods

Visible fats are those we can see in foods or can

easily see have been added to foods, such as

dressing or chicken skin

Hidden fats are those added to processed or

prepared foods to improve texture or taste, which

we may not be aware of, or that occur naturally

Read the Nutrition Facts Panel on foods carefully

• Lower-fat versions of foods may not always

be lower in Calories

Comparison of Foods

Terms Associated with Fat

Fat-free: less than 0.5 g fat

Low-fat: 3 g or less fat

Reduced fat: 25% less fat than standard product

Light: 1/3 less calories or 50% less fat than

standard product

Limit Saturated and Trans FatsReduce your intake of saturated fats (7-10% of

total calories)

Foods that are high in saturated fats:

Animal products: beef pork, and lamb

Grain products: Pastries, cookies, muffins,

tortilla chips, popcorn, and crackers

Vegetable products: Fried veggies, breaded

veggies, or vegetables drenched in sauces

Note: Avoid trans fatty acids entirely!

Role of Fats in Chronic Disease

The chronic disease most closely associated with

diets high in saturated fat is cardiovascular

disease and hypertension (high blood pressure).

Modifiable risk factors for cardiovascular disease include:

• Being overweight

• Physical inactivity

• Smoking

• Type 2 diabetes

• Inflammation in the body

• Abnormal blood lipids

Cardiovascular Disease

Chapter 6 - Proteins

What Are Proteins?

Proteins

• Large, complex molecules composed of

amino acids found in the cells of all living

things

• Critical components of all the tissues of the

human body

• Function in metabolism, immunity, fluid

balance, and nutrient transport

• In certain circumstances, provide energy

• Contain a special form of nitrogen our bodies

can readily use

Amino AcidsAmino acids are the nitrogen-containing molecules

that combine to form proteins. There are 20 amino

acids in the body.

Essential amino acids

• Cannot be produced by our bodies

• Must be obtained from food

• 9 of 20 amino acids in our bodies are

essential

Nonessential amino acids

• Can be made by our bodies

Structure of an Amino Acid

Examples Structures of some Amino Acids

Amino Acids of the Human Body

How Are Proteins Made?

Gene expression: the process of using a gene to

make a protein

Transcription: use of the genetic information

(genes) in DNA to make RNA

Translation: conversion of genetic information in

RNA to assemble amino acids in the proper

sequence to synthesize a protein on the ribosome

Synthesis and Breakdown

Incomplete versus Complete Proteins

Incomplete protein: does not contain all essential

amino acids in sufficient quantities

• Growth and health are compromised

• Considered a "low-quality" protein

Complete protein: contains sufficient amounts of

all nine essential amino acids

• Considered a "high-quality" protein

• Ex: Egg whites, meat, poultry, fish, milk, soybeans,

quinoa

Protein Synthesis Can Be Enhanced

Complementary proteins: two protein sources that

together supply all nine essential amino acids

• Example: beans + rice

Combining Complementary Foods

Why Do We Need Proteins?

• Cell growth, repair, and maintenance

• Enzymes and Hormones

• Fluid and electrolyte balance

• pH balance

• Antibodies to protect against disease

• Defensive proteins of the immune system

• Energy source

• Transport and storage of nutrients

Nitrogen

consumption

Nitrogen

excretion

Nitrogen

excretion

Nitrogen

excretion

Nitrogen

consumption

Nitrogen

consumption

Nitrogen Balance

Too Much Dietary Protein Can Be Harmful

The risks of too much dietary protein include

• High cholesterol

• Diets high in protein from animal sources are

associated with high blood cholesterol

• Kidney disease

• High-protein diets are associated with an increased

risk of kidney disease in people who are susceptible

There is no evidence that high-protein diets lead to

bone loss, except in people consuming inadequate

calcium

How Much Protein Should We Eat?

Nitrogen balance describes the relationship

between how much nitrogen (or protein) we

consume and excrete each day.

Recommended Dietary Allowance (RDA)

• 0.8 grams of protein per kilogram of body

weight per day

• 10–35% of total energy intake should be

from protein

Recommended Protein Intakes

Generally, vegetarian strength athletes require

the most dietary protein.

How Much Protein Should We Eat?

Most Americans meet or exceed the RDA for dietary

protein

This is true for many athletes as well

Certain groups of athletes, such as distance runners,

figure skaters, female gymnasts, and wrestlers who

are dieting, are at risk for low protein intake

Protein: Much More Than Meat!

Some legume sources of protein include:

• Soybeans, kidney beans, pinto beans, black

beans, chickpeas, lentils, green peas, and

black-eyed peas.

Various nuts are also a good source of protein.

Some research indicates that consuming 2-5

ounces of nuts/week can reduce the chances of:

• Cardiovascular disease

• Type 2 diabetes

Protein Content of Common Foods

Can Vegetarian Diets Provide Protein?

Vegetarianism: restricting the diet to foods of plant

origin

• There are many versions of vegetarianism

• There are many reasons to adopt a vegetarian diet

Types of Vegetarian Diets

Health Benefits of Vegetarianism

• Lower intake of fat and total energy

• Lower blood pressure

• Reduced risk for heart disease

• Reduced risk for some types of cancer

• Fewer digestive problems

• Reduced risk for kidney disease

Disorders Related to Protein Intake

Protein-energy malnutrition: a disorder caused by

inadequate intake of protein and energy

There are two common, serious forms

• Marasmus

• Kwashiorkor

Disorders Related to Protein Intake

Marasmus: disease resulting from severely

inadequate intakes of protein, energy, and other

nutrients

It is characterized by extreme tissue wasting and

stunted growth and development

Disorders Related to Protein Intake

Kwashiorkor: disease resulting from extremely low

protein intake

Kwashiorkor symptoms include

• Some weight loss and muscle wasting

• Edema resulting in distention of the belly

• Retarded growth and development

Kwashiorkor is often seen in children in developing

countries

Marasmus and Kwashiorkor

Do Athletes Need More Protein?

Simple answer: Yes

Should they get this extra protein through

supplements?

Not necessarily. Most North Americans eat much

more protein than what they require (almost twice the

Recommended Dietary Allowance).

A balanced diet is usually sufficient; however, protein

supplements can be very convenient and cost

effective.

Watch: “You Are What You Eat”