Acids in Nutrition

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22 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Proteins and Amino
Acids in Nutrition

Dr. David L. Gee

FCSN 245

Basic Nutrition


Biologically
:


proteins are the most important
molecues in the body


“action molecues”


Nutritionally
: (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
other


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


3
-
dimensional structure


Determined by AA sequence


Specificity

of a protein’s
function


Diversity

of protein functions

Other Amino Acid Facts


9 “
Essential
” 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


“Transcription”


making a copy of the information


messenger RNA


“Translation”


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


Examples:


Sickle Cell Anemia


Cystic Fibrosis


Familial Hypercholesterolemia


LDL
-
receptor


Human Genome Project


Map the genome


20
-
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


Non
-
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:
Prevalence


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)


70
-
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


Advantages:


speed


more specific, less random


interspecies gene transfer

Benefits of Genetically
Engineered Foods


Reduce use of pesticides


Bacillus thuringiensis (Bt)


“natural” pesticide used by organic
farmers


Bt produces a protein toxic to insect
larvae


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
plants


“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


Catalysts


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


Hormones


Protein Hormones


Insulin


Glucagon


Amino Acid Derived Hormones


serotonin


adrenaline

Protein Functions


Antibodies & Immune
System


impaired immune system with protein
deficiency


Fluid Balance


albumin


edema

Protein Functions


Acid
-
Base Balance


buffer


acidosis & alkalosis


Energy &
Glucose


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


starvation


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…


Digestibility


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
Beans

© 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
diets


Animal welfare/ethical considerations


Economic reasons


World hunger issues


Religious beliefs


Vegetarian Diets:

Potential Health Benefits


Obesity


% 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
-
C


Hypertension


42% non
-
veg with hpt, 13% vegetarians


Also lower prevalence for


Diabetes


Cancer

Vegetarian Diets:

Consumer Trends
-

2000


2.5% of adult Americans are vegetarians


4.8 million people


Slightly less than 1% are vegans


20
-
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
-
1996


>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
-
defined
Vegetarians


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


Non
-
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


Lacto
-
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
-
based


Nutritional Concerns


protein quality


probably OK, quantity may be an issue


calcium


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


iron


no meat, plant sources (leafy greens), cereals


vitamin B
-
12


probably OK, cereals & supplements

Protein Deficiency


Protein
-

Energy Malnutrition


> 500 million children with PEM


33,000 die per day with PEM


Two major forms of PEM


Kwashiorkor


Marasmus

Protein Deficiency


Kwashiorkor


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


Protein low, Calories OK


Symptoms


edema


enlarged fatty liver


light colored hair


low tyrosine/melanin


skin lesions


Protein Deficiency


Marasmus


Both Protein and Calories
low


inadequate food intake


Symptoms


wasting of lean and fat tissue


weak, anemic, low metabolism


death due to secondary
infections

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
-
0.6gP/kg


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
diets?
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


1.2


1.5 gPRO/kg BW


175 lbs = 80kg = 96
-
120gP/day


If 3000 Cal diet = 13
-
16% of Calories


Adequate energy, especially Carbs


6
-
7g CHO/kg BW


175 lbs = 480

560 g CHO


If 3000 Cal diet = 64%
-

75%


Proper cellular hormonal balance


Genetics


Weight training


Cheating (anabolic steroids, androstenedione
(prohormone)