Acids in Nutrition


Oct 22, 2013 (4 years and 8 months ago)


Proteins and Amino
Acids in Nutrition

Dr. David L. Gee

FCSN 245

Basic Nutrition


proteins are the most important
molecues in the body

“action molecues”

: (at least in the US)

proteins are of the least concern for
macronutrients in the diet

protein deficiency very unusual

excess protein generally not a problem

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

Protein Structure

Polymer of amino acids

Amino acid structure

amino group (N)

acid group

side chain

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

Amino Acids

20 different amino acids

Differ by type of side chain

Water soluble AA

charged side groups

Can form ionic bonds

sulfer containing side groups

Can form disulfide bonds

Fat soluble AA

Fat soluble AA interact/dissolve with each

These interaction/bonds between AA side chains
cause proteins to form specific shapes

Protein Structure

Primary Structure

sequence of amino acids

Secondary Structure

helical coil

Protein Structure

Tertiary Structure

folding of coil

dimensional structure

Determined by AA sequence


of a protein’s


of protein functions

Other Amino Acid Facts

9 “
” amino acids

Amino acids that cannot be made and must be
consumed in the diet (dietary essential)

peptide bonds

link amino acids together

proteins typically contain a few hundred
amino acids

infinite combinations of amino acids

tremendous diversity of protein types

Protein Synthesis:

how proteins are made

DNA, genes, chromosomes

where the information is stored


making a copy of the information

messenger RNA


reading the information and making the protein

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

Genetic Disorders:

errors in the stored information


Sickle Cell Anemia

Cystic Fibrosis

Familial Hypercholesterolemia


Human Genome Project

Map the genome

25,000 genes in human genome (10/04)

Fix the genes ???

Have you eaten GM foods?

Are GM foods safe?

2003 survey of US consumers

partisan Pew Initiative on Food and Biotechnology

48 % opposed to GM foods, 25% in favor

2001 58% opposed to GM foods

24% say they’ve eaten GM foods

58% say they haven’t

Genetic Modified Crops:

In 2003 (USDA) genetically modified crops accounted for:

40% of all corn

81% of soybeans

73% of cotton

In 2002

35% of corn

55% of soybeans

Grocery Manufactures of America (2003)

80% of processed foods contain GMO

USDA approval for

potatoes, tomatoes, melons, beets

nicotine free tobacco

Genetic Engineering:

Food and Health Issues

Traditional animal and plant breeding

Alteration of genetic material with
tools of biotechnology



more specific, less random

interspecies gene transfer

Benefits of Genetically
Engineered Foods

Reduce use of pesticides

Bacillus thuringiensis (Bt)

“natural” pesticide used by organic

Bt produces a protein toxic to insect

Gene for Bt toxin incorporated into
corn, etc.

Corn plant produces Bt protein toxin

Benefits of Genetically
Engineered Foods

Reduce erosion of topsoil due to tilling

tilling for weed control

Monsanto’s “Roundup” (glyphosate)

inhibits plant’s ability to make tryptophan

tryptophan is an EAA for humans

Roundup resistant plants (soybeans)

spliced bacterial gene into plant that is resistant to
effect of Roundup (still able to make tryptophan)

Benefits of Genetically
Engineered Foods

Improved nutritional quality of

“golden rice”

rice with B
carotene gene

improved protein quality & quantity

higher in vitamins

Improved sensory properties

Tomato and strawberry flavor & texture

Genetically Engineered Foods:

Environmental Concerns

Pesticide resistant insects

Unintentional environmental effects

monarch butterfly larvae

lab study

affect beneficial insects (ladybugs)

development of “superweeds”, “superbugs”

Control of Food Production

Terminator gene

GMO plants with gene to produce sterile seeds

Biotech firms with too much control?

Genetically Engineered Foods:

Health Issues

(Theoretical problems?)

Lack of long term feeding trials

animal studies, human studies

Food allergies

antifreeze protein from fish

Labeling Issue

Pros: consumer has the right to know

Cons: unnecessary, no evidence of
environmental/health concerns, will hurt
sales and stymie further development

Protein Functions

Enzymes & related proteins


Membrane transporters

Cell receptors

©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.

Transport Proteins

sodium pumps

Protein Functions

Structural Proteins

Muscle fiber proteins

Connective proteins

Protein Functions


Protein Hormones



Amino Acid Derived Hormones



Protein Functions

Antibodies & Immune

impaired immune system with protein

Fluid Balance



Protein Functions

Base Balance


acidosis & alkalosis

Energy &

Unlike fats, amino acids can be converted into
glucose (required for CNS/brain function)


low carbohydrate diets

body cannibalizes body proteins to make glucose

Protein and Nutrition

Daily protein needs

Quantity of protein

Quality of protein

Protein Quality

How well a protein meets the body’s
need for health, growth, etc…


Amino acid composition

Essential Amino Acids composition

Protein Quality

Measures of protein quality

Biological Value (BV)

Measures body retention of food protein

BV=100 => 100% of food protein retained

Protein Efficiency Ratio (PER)

Measures ability of protein to support growth

g growth/g protein fed

PER=3 => 3g growth per g or protein fed

Protein Quality: BV

Protein Quality: PER

Protein Quality

Vegetarian Diets

Is there a protein problem?

Plant proteins are “Incomplete proteins”

Complementary Proteins

Example: Mexican Food

Tortilla: low lysine, hi methionine

Beans: low in methionine, hi lysine

Tortillas & Rice with Refried

© 2002 Wadsworth Publishing / Thomson Learning™

Hummus (garbanzo beans) and
Pita Bread (wheat)

© 2002 Wadsworth Publishing / Thomson Learning™

Peanut butter (legume)
sandwich (wheat)

© 2002 Wadsworth Publishing / Thomson Learning™

Vegetarian Diets:

Why become a vegetarian?

Health benefits

Environmental concerns about meat based

Animal welfare/ethical considerations

Economic reasons

World hunger issues

Religious beliefs

Vegetarian Diets:

Potential Health Benefits


% of obesity lower in vegetarian populations

Cardiovascular Disease

Risk of CHD 31% lower in vegetarian men and 20%
lower in vegetarian women

Lower LDL
C, lower HDL


42% non
veg with hpt, 13% vegetarians

Also lower prevalence for



Vegetarian Diets:

Consumer Trends


2.5% of adult Americans are vegetarians

4.8 million people

Slightly less than 1% are vegans

25% of adult Americans eat 4 or more
meatless meals weekly

“What do vegetarians in the United
States eat?”

Am J Clin Nutr. 78S:626
632 (2003)

Continuing Survey of Food Intake by
Individual (CSFII): 1994

>13,000 subjects

2 day food records

2.5% considered themselves as vegetarian

36% of self
defined vegetarians actually
consumed no meat

~4% of total consumed no meat

“What do vegetarians in the United States eat?”

Characteristics of Self

Vegetarians were thinner

BMI: 23 vs 26

Consumed more CHO

57% vs 50%

Less fat and saturated fat

27% vs 33% and 9% vs 11%

More vitamin A, carotene, vitamin E, vitamin C,
folate, dietary fiber and less cholesterol

Vegetarian Diets: Types

red meat vegetarian

poultry, fish, dairy, eggs OK

Nutritional Benefits

Less fat, saturated fat, cholesterol

Nutritional Concerns

no special nutritional problems

May not be any better than typical US diet

may be high in fat, sat’d fat, salt

cooking methods

junk foods, convenience foods

Vegetarian Diets: Types

ovo vegetarian

Milk & eggs OK

Nutritional Benefits

Like non
meat vegetarians

Nutritional Concerns

No special nutritional problems

May be high in fats, sat’d fats

cheese & eggs

Vegetarian Diets: Types

Strict Vegetarian: Vegan

no animal foods

Nutritional Benefits

Low fats, high fiber, plant

Nutritional Concerns

protein quality

probably OK, quantity may be an issue


no dairy, plant sources (leafy greens, soy), fortified foods (soy, rice milk)


no meat, plant sources (leafy greens), cereals

vitamin B

probably OK, cereals & supplements

Protein Deficiency


Energy Malnutrition

> 500 million children with PEM

33,000 die per day with PEM

Two major forms of PEM



Protein Deficiency


Ghana “the evil spirit that infects the first
child when the second child is born”

Protein low, Calories OK



enlarged fatty liver

light colored hair

low tyrosine/melanin

skin lesions

Protein Deficiency


Both Protein and Calories

inadequate food intake


wasting of lean and fat tissue

weak, anemic, low metabolism

death due to secondary

Protein Needs

RDA = 0.8g Pro/kg BW

Or ~ 15% of calories

M = 55 gP/d F = 45 gP/d

Safety factor accounts for:

individual differences

varied protein quality

average requirement 0.5

Typical Intake: 65

110 gP/d

Athlete’s Protein Needs ?

Most sport nutritionists recommend

1.0 to 1.5 g protein/kg BW

RDA = 0.8 gP/kg BW

Example of athlete’s protein needs

175 lb = 80 kg athlete

80 kg x 1.5gP/kg =

120 g protein needed per day

So do athletes need to supplement their
Usually not.

3500 Cal/d x 15%Pro = 525 Cal Pro

525 Cal P / 4 Cal/gPro =

131 g pro in normal diet

For maximal muscle gain:

Adequate protein


1.5 gPRO/kg BW

175 lbs = 80kg = 96

If 3000 Cal diet = 13
16% of Calories

Adequate energy, especially Carbs

7g CHO/kg BW

175 lbs = 480

560 g CHO

If 3000 Cal diet = 64%


Proper cellular hormonal balance


Weight training

Cheating (anabolic steroids, androstenedione