nutrition: proteins and amino acids

what are proteins and why are they important?

proteins are large molecules made of amino acids

• build and repair tissues

• support the immune system

• regulate body processes

  • ex: how your body uses energy

how do amino acids build proteins?

• peptide bonds

  • link amino acids

• strands of amino acids don’t remain straight

  • coils

  • folds

  • each shape does a different function

• side chain electrical charge

• activation

primary protein structure

sequence of a chain of amino acids

protein digestion

starts in the stomach and small intestine (duodenum)

• breaks down protein until it is a single amino acid again

3 main enzymes break down food proteins into polypeptides

protein digestion: 3 main enzymes and functions

• pepsin: secreted by the stomach

  • major enzyme

  • helps break down with hydrochloric acid in the stomach

• trypsin and chymotrypsin: secreted by the pancreas into amino acids

  • absorbed into the body

protein bioavailability

• how much protein is digested, absorbed, and used by the body

• important for building and repairing body tissues

protein bioavailability: animal proteins

high bioavailability:

• milk proteins (95%)

• meats (94%)

• whey proteins (67%)

animal products are much better for protein bioavailability

protein bioavailability: plant proteins

lower bioavailability:

• soy or pea (73%)

• wheat (65%)

functions of body protein

• structure

• enzymes

• hormones

• antibodies

• fluid balance

• acid-base balance

• channels and pumps

• transport

functions of body protein: structure and movement

• the protein that makes up your muscles, skin, bones, tendons, and more

• collagen strengthens skin, joints, and blood vessels

  • tensile strength

functions of body protein: repair and recovery

• protein turnover - body needs protein daily to build new cells - gain muscles

• breakdown-recovery-synthesis

• the body needs protein daily to build new cells

functions of body protein: gene expression and enzymes

• protein help turn genes on/off and act as enzymes for metabolism

• affects how the body responds to meds, break down food, or fight illness

• enzyme deficiencies (like PKU) require strict dietary protein control

functions of body protein: building enzymes and hormones

+other chemical and neurotransmitter messages

• hormones such as insulin and serotonin - affects our mood

• getting muscles and body moving helps with stress

• protein higher than body fat is ideal

• voluntary muscle contractions

functions of body protein: building antibodies

• destroy one specific invader

• each antibody is made to recognize and destroy one specific invader (like virus or bacteria)

• the more proteins = the stronger your immune system and the less likely you’ll be sick

• malnutrition: low in protein

functions of body protein: maintaining acid-base balance

aka blood pH

• the body needs to keep blood pH in a very tight range (around 7.35-7.45)

• protein buffers in the blood

  • acidosis (too much acid in the blood)

    • proteins → too much = inflammation + gout

  • alkalosis (too much base in the blood)

    • vegetables

functions of body protein: blood clotting

proteins clot blood, prevent bleeding

• one way as to how we don’t bleed out

functions of body protein: transport substances

hemoglobin

• carries oxygen and other substances in your blood

lipoprotein

nitrogen balance

• protein in = protein out

• shows if the body is building or breaking down tissue

• when nitrogen intake and output are equal, a person is in nitrogen equilibrium

nitrogen positive balance

more in than out - too much protein

• occurs during growth, pregnancy, and healing

  • times when we need a lot of protein

• ex: child healing after surgery needs extra protein

nitrogen negative balance

more out than in

• starvation, burns, severe illness

• ex: burn patient, losing protein - needs high-protein diet

• bodies are degrading - prone to infection

recommended intake of protein

1.2 - 1.6 g/kg body weight

• 0.8 g/kg of body weight is minimum

protein is our only source of essential amino acids and nitrogen

exercise and protein

• eat ~6g of protein and ~35g of carbs before exercise

• eat ~20g protein snack/beverage with adequate carbs to repair/stimulate muscle proteins and replenish muscle glycogen stores after exercise (within first 30 min)

  • low-fat milk, yogurt, small sandwich, energy bar with 10g protein, or sports nutrition shake

complete proteins

contains all 9 essential amino acids

• found in meat, fish, egg, and dairy

9 essential amino acids

the body cannot produce them on their own

• histidine

• isoleucine

• leucine

• lysine

• methionine

• phenylalanine

• threonine

• tryptophan

• valine

complementary proteins

two or more proteins that in combination have all 9 essential amino acids

• ex: rice and beans

types of amino acids

• essential amino acids

  • need to know that there are 9

• conditionally essential amino acids

• non-essential amino acids

examples of incomplete proteins

combine together throughout the day to make it complete

• nuts and seeds

• whole grains (like brown rice or whole-wheat bread)

• vegetables

• legumes in the form of lentils, peas, and beans

• non-dairy milks

complementary protein combinations

1. rice and beans

2. pasta, vegetables, and parmesan cheese

3. oatmeal

4. whole grain bread and peanut butter (and jam)

5. yogurt and nuts

6. whole grain cereal with dairy milk

7. hummus and whole grain pita

protein supplements

• does not improve performance

• not effective for weight loss

• body is designed to eat foods together - may not have a lot of calcium for the bones

amino acid supplements

• body designed to work with whole proteins

• no safe level of amino acid supplementation

• potential risks associated with intake

• lysine and tryptophan

health effects of protein: protein deficiency

consequences:

• protein-energy malnutrition

  • not getting enough calories

• marasmus and kwashiorkor

  • not getting enough protein

health effects of protein: heart disease

• animal-protein intake

• homocysteine levels

  • coffee’s role

• arginine levels

health effects of protein: cancer

protein-rich foods, not protein content of diet

health effects of protein: adult bone loss (osteoporosis)

• increase in calcium excretion

• protein to calcium ratio

health effects of protein: kidney disease

acceleration of kidney deterioration

health effects of protein

• protein deficiency

• heart disease

• cancer

• adult bone loss (osteoporosis)

• weight control

• kidney disease

protein and amino acid supplements: building muscle

• muscle work vs protein supplements

• protein powders

  • athletic performance

• whey protein