What Are Proteins?  Proteins: large, complex molecules composed of amino acids DNA determines structure  Contain nitrogen  20 different amino acids (AA) are used to make proteins Building blocks of proteins

Amino Acids  Amino acids are linked (bound) together by special chemical bonds: Peptide bonds  The 20 amino acids can be bound together to make up to 50,000 different protein molecules

Amino Acids  The structure of an amino acid begins with a central carbon atom. 4 attachment sites  The central carbon is surrounded by: 1. a hydrogen atom 2. an acid group 3. an amine group 4. a side chain (R group) that is unique to each amino acid ○ Variations give each AA its distinct properties Identical on every amino acid

Amino Acids

 Essential amino acids: cannot be produced by our bodies Must be obtained from food 9 amino acids  Nonessential amino acids: can be made by our bodies Using parts of nitrogen of other amino acids ○ Transamination 11 amino acids

Amino Acids Conditionally essential amino acids: when nonessential amino acids can’t be made to meet body needs

How Are Proteins Made?  Proteins are long chains of amino acids.  Amino acids are joined to each other by peptide bonds.  The structure of each protein is dictated by a DNA of a gene. Genes carry the instructions for amino acid sequencing

How Are Proteins Made?  Dipeptide Two amino acids  Tripeptide Three amino acids  Oligopeptide Four to forty nine amino acids  Polypeptide 50 to 100 amino acids Results in complex shapes

Proteins Organization  The three-dimensional shape of a protein: is determined by the amino acids in the protein is critical to the proper function of the protein ○ Tendons vs. red blood cells can uncoil due to damage by heat, acids, heavy metals, alcohol, and other substances ○ Denatured protein = lost function **Denaturation**

Protein Structure Example

Sickle-shaped cell

Protein Denaturation

Why Do We Need Proteins?  contribute to cell growth, repair, and maintenance Growing children, damaged cells, new cells

Why Do We Need Proteins?  act as enzymes and hormones Inborn errors of metabolism (IEOM) Galactosemia

Enzymes

Why Do We Need Proteins?  help maintain fluid balance Proteins help pull fluids out of tissues into blood vessels and cells ○ If insufficient protein intake: edema

Why Do We Need Proteins?  Transport nutrients Electrolytes, vitamins, minerals, glucose  Help maintain pH balance Act as buffers against acids and bases  Protect against disease Antibodies  Serve as an energy source Gluconeogenesis We want to “spare” protein

Proteins in the Diet  Our bodies do not store proteins, but they do have a small supply of amino acids in reserve Pool of amino acids  All essential amino acids need to be in the pool Limiting amino acid – essential amino acid that is missing or in shortest supply ○ May slow or halt protein synthesis (video)video

Limiting Amino Acids

Proteins in the Diet  Most proteins contain all of the essential amino acids (EAAs)!! (except gelatin)  Complete proteins supply all the EAAs needed to meet biologic requirements when consumed at recommended amounts “high quality” Animal-based, except soybeans/quinoa  Incomplete proteins also supply all of the EAAs, but usually one AA is limiting (low) “low quality” Plant-based

Proteins in the Diet

Soy Foods  High quality, complete protein  Contain vitamins, minerals, phytochemicals  What about estrogen/hormones? Isoflavones not same as human estrogen Will not turn guys into gals  Up to 3 servings per day

Protein Supplementation  Muscle growth = PRO synthesis > PRO breakdown  Achieved with weight training and regular meal consumption PRO + CHO  Eating excess protein does not lead to muscle gain  May be helpful for certain people

How Much Protein Should We Eat?  Proper protein intake depends on: age activity level health status  Dietary Reference Intake (DRI) 0.8 g protein per kg body weight (most adults) g/kg for athletes 10% – 35% of total energy intake should be from protein (AMDR)

How Much Protein Should We Eat?  To convert pounds to kg, simply divide by 2.2  A person weighing 160 pounds is how many kg? 160 lbs ÷ 2.2 = ~73 kg  If this person is an average adult, what is his/her PRO requirement? 73 kg x 0.8 g PRO/kg = 58 g PRO/day

How Much Protein Should We Eat?  People who require more protein include: children adolescents pregnant or lactating women Athletes ○ Carry more O 2, make glucose, repair/make new tissue Vegetarians (some) ○ Plant proteins less well digested More needed for growth and development

Sources of Protein  Good sources of protein include: meats dairy products (milk, egg whites) soy products (considered “complete”) legumes (all varieties of dried beans, peas, peanuts) ○ Also considered a veggie choice!! whole grains (compliment the legumes) Nuts (Don’t discount leafy greens)

Vegetarian Diets  Vegetarianism: focusing the diet on foods of vegetable origin (including fruits, grains, nuts)  There are many versions of vegetarianism.  There are many reasons to adopt a vegetarian diet.

Vegetarian Diets

Why Vegetarianism?  People choose vegetarianism for: ethical reasons concerns over food safety/antibiotics ecological reasons religious reasons health benefits

Health Benefits of Vegetarianism  Reduced risk of: obesity, type 2 diabetes heart disease and high blood pressure some types of cancer kidney disease, kidney stones, gallstones  Fewer digestive problems  Current guidelines emphasize eating plant protein sources

Considerations of Vegetarianism  Vegetarian diets can be low in some vitamins and minerals.  Vegetarians (and everyone else) must carefully plan a balanced and adequate diet.  Vegetarians (and everyone else) can use soy products as a protein source.

Diet Comparison S.A.D (Standard American Diet) Vegetarian/Vegan Nutrients of Concern 1.Potassium 2.Vitamin A 3.Vitamin C 4.Vitamin E 5.Vitamin K 6.Fiber 7.Calcium 8.Vitamin D 9.Iron Nutrients of Concern 1.Vitamin B12 2.Zinc 3.Calcium 4.Vitamin D 5.Iron

Vegetarian Food Guide Pyramid

Vegetarian Eating Guides PCRM’s Power PlateVegetarian Society of the United Kingdom Don’t forget B12!!!

Protein Imbalances  Too little protein: Protein-energy malnutrition (PEM) ○ Marasmus ○ Kwashiorkor ○ Due to poverty, chronic disease, eating disorders  Too much protein

Marasmus  Starving to death  Insufficient PRO, energy, & nutrients  Little to no subcutaneous fat  Reduced brain growth  Also seen in hospitalized patients

Kwashiorkor  Not enough protein  Energy needs just marginally met  Swollen abdomen  Impaired growth, rash, impaired immune system, fatty liver

Too Much Protein  Do not exceed 2 grams/kg body weight  Why not? Not getting enough plant foods Risk imbalances in diet

Can You Eat Too Much Protein? The risks of too much protein may include:  high cholesterol and heart disease Due to high saturated fat, low fiber intakes  possible bone loss High-protein diets may cause excess calcium excretion leading to bone loss.

Can You Eat Too Much Protein?  The risks of too much protein may also include kidney disease. High-protein diets can be difficult for people with kidney problems. ○ Due to the demand placed on stressed kidneys to flush out excessive urea There is no evidence that high-protein diets cause kidney disease in healthy people.  Increased cancer risk?

RD Chuckle