Lecture 10 - Protein and Vegetarian Diets

why do we need dietary protein?

for muscle and bone structure, enzymes (carbonic anhydrase) and hormones (ADH) are made of proteins, transport and receptors, antibodies, also use it for energy

amino acid structure

each one has a carbon atom bound to four chemical groups, a hydrogen atom, amino group, acid group and a side chain that is unique to each amino acid, the amino group contains to a nitrogen atoms

essential/indispensable amino acids

those amino acids that cannot be made by the human body so you only get it through your dietary intake, there are 9 of them

transamination

process by which an amino group from one amino acid is transferred to a carbon compound to form a new amino acids, this is how non essential amino acids can be formed from essential amino acids

tyrosine

non essential because it can be synthesized from the essential amino acid phenylalanine, if the phenylalanine intake drops then tyrosine will be essential too

which essential amino acids at the most difficult to obtain?

lysine and methionine

protein structure

to form proteins, amino acids are linked together by a peptide bonds, many of them linked together create a protein (polypeptide)

digestion of protein

they are broken down to individual amino acids, dipeptides and tripeptides, they enter the enterocyte (RBC) via transporters and more than one amino acid sometimes competes for a single transporter, after they enter it the dipeptides and tripeptides are broken down to amino acids and the individual amino acids enters the blood stream and travel to the liver and then to the rest of the body

food allergies

protein is absorbed intact causing the immune system to be stimulated so when the food is consumed again it triggers an allergic reaction, symptoms can include vomiting and diarrhea, rash or hives, difficulty breathing and drop in blood pressure while in severe cases it causes anaphylaxis

common allergens

egg, milk, mustard, peanuts, crustaceans and molluscs, fish, seasame seeds, soy, sulphites, tree nuts, wheat and triticale

amino acid pool

energy production, synthesis of glucose or fatty acids, synthesis of nonprotein molecules that contain nitrogen

amino acid shortage

limits the ability synthesize a protein that is high in its amino acid

what nutrients control gene expression?

zinc, vitamin A, D, PUFA and glucose

zinc

intake increased expression of metal binding proteins

vitamin A

regulates expression involved in the development of immune cells

vitamin D

regulates calcium transport proteins

PUFA

regulate lipid metabolism

glucose

influences insulin expression

deamination

occurs before amino acids are used for energy, it produces ammonia which is toxic, it gets converted to urea in the liver and that is transported to the kidney for excretion

protein function

structural proteins (ex; collagen in bone), enzymes, transport proteins, protective proteins (ex; skin and antibodies), contractile proteins (muscle), hormones (insulin), fluid and pH regulation

kwashiorkor

disease the first child gets when the second is born, the first child is weaned off breast milk to a low protein diet, the diet is sufficient in energy but low in protein, this causes a swollen belly where there is fluid accumulation in tissue because of low blood proteins and lipid accumulation in liver because of lack of transport proteins

marasmus

starvation causing lack of energy and protein

celiac disease

gluten intolerance, diagnoses by detection of antibodies to gluten and biopsy of the small intestine to confirm damage to villi, the only way to treat it is by completely avoiding gluten, it increases a person’s risk of gastrointestinal cancers, low bone density and other autoimmune disorders

gluten free foods

gluten is found in wheat, rye and barley, gluten free foods and diets have become a fad, leading to self diagnosis and persons not eating gluten containing products, this is a problem because diagnosis for celiac is not possible as antibodies to gluten disappear when gluten containing foods are not eaten

nitrogen balance

occurs when nitrogen intake equals nitrogen excretion, best determinant of protein requirements

AMDR

10-35% kcal from protein, range to allow for different dietary patterns and preferences, if its more than 35% that means higher in %kcal from saturated fat so protein is coming from animal sources and lower in % kcal from carbs than recommended

amino acid as an indicator of protein requirement

for protein synthesis to take place all indispensable or essential amino acids are required at an adequate dose, this dose indicates the protein requirement, use an indicator amino acid with a C-13 label, when intake is too low to provide essential amino acids the C-13 isotope appears in breath as 13CO2 because AA is used for energy rather than protein synthesis, as protein intake increases that 13CO2 will decrease and the protein intake at which 13CO2 levels off is equivalent to the protein requirement

protein quality

determined by the limiting essential amino acid

complete proteins

contains all essential amino acids in proportions that support protein synthesis (animal based proteins)

digestible indispensible amino acid (DIAAS)

takes into account amino acid composition and ileal digestibility

digestibility

feed protein to human or animal (pig) and determine how much AA is unabsorbed at the end of the small intestine (ileum), ex; if 10% of amino acid is detected at the end of small intestine then 90% is absorbed and the digestibility is 0.90

protein rating

protein in a reasonable daily intake x protein efficiency ratio

vegetarians

no animal products

lacto-ovo-vegetarians

eggs and milk included but no fish, meat, poultry

pesco-vegetarian

fish and seafood

vegans

avoid all animal products

what are at risk nutrients when someone is a vegetarian?

protein, vitamin B12, calcium, vitamin D, iron, zinc and omega 3 fatty acids

underweight BMI

less than 18.5

normal BMI

between 18.5 and 24.9

overweight BMI

between 25 and 29.9

obese BMI

over 35

what are the pros and cons of using BMI as an indicator of obesity?

it is a quick, easy and reproducible method but it does not indicate type of tissue or distribution, there is heterogeneity with BMI so some with high BMI don’t have high risk while others do (ex; bodybuilders have high BMI but mostly muscle so not at risk for disease)

obesity associated risks

it increases risk for type 2 diabetes, cardiovascular disease and cancer

hyperinsulinemia

increased insulin secretion to compensate for high blood glucose, if it fully compensates it allows blood glucose to go back to normal levels, if it is only partial the remaining high glucose is pre diabetic and if insulin secretion is inadequate so might be hyperinsulinemia it would indicate type 2 diabetes

how does obesity affect carb and fat metabolism?

it causes increased FFA release and inflammation, there is always a steady release of FFA from adipose tissues to provide the body with a constant source of energy and levels are present to the amount of adipose present, with weight gain there is an expansion of size of cells, those with higher levels of adiposity release FFA than lean individuals, these higher levels of FFAs cause changes in lipid and glucose metabolism, inflammation increase with adiposity

how does inflammation increase with adiposity?

large mass of adipose tissue creates zones of hypoxia (low O2), this leads to cell death triggering the recruitment of immune cells, this causes inflammation and secretion of inflammatory proteins to the rest of the body

how does obesity increase the risk for type 2 diabetes?

obesity means adipose cells increased in size, this increases inflammation and FFA release, this causes insulin resistance in liver muscle and adipose tissue, increased FFA utilization by muscle and liver for oxidation and storage as triglycerides. this causes lipotoxicity which causes beta oxidation to fail in the pancreas + further increase insulin resistance causing type 2 diabetes

insulin resistant

increased FFA release, causes increased VLDL secretion and gluconeogenesis, causes increased FFA uptake and decreased glucose uptake which overall elevates blood glucose

hormone sensitive lipase

acts on cells leading to FFA release

how does obesity increase risk of CVD?

it increases FFA, increasing uptake by the liver and in turn increasing VLDL (bad cholesterol) secreted by the liver

VLDL in normal lipoprotein metabolism

the enzyme lipoprotein lipase hydrolyzes the triglycerides and fatty acids enter the tissue, some cholesterol is also released at the same time and is take up by HDL and returned to the liver, as the triglycerides are depleted from the VLDL particle it is converted to IDL, the IDL is further depleted of triglycerides and becomes a LDL which gets taken up by the liver and metabolized

VLDL in abnormal lipid metabolism

when levels are high there are the usual lipid transfers that occur in normal metabolism but there are also some atypical transfers, cholesterol from HDL instead of being taken up the liver is transferred to VLDL particles resulting in cholesterol depleted HDL which is rapidly cleared from the blood resulting in low HDL levels, triglycerides from VLDL are transferred to LDL resulting in triglyceride-enriched LDL, they are acted on by hepatic lipase which removes the triglycerides and results in the formation of small dense LDL which is atherogenic and increases risk of CVD

small dense LDL

because it is small it can easily penetrate the artery wall to start plaque formation via fatty streaks which means increased risk of CVD

what lipids increase risk of CVD?

high VLDL, low HDL and high sd-LDL

which cancer does obesity increase risk the most?

colorectal and breast (postmenopausal)

cancer

disease characterized by a series of genetic mutations that result in a cell that; de-differentiates, becomes proliferative, can not repair its damaged DNA and becomes resistant to apoptosis

de-differentiates (cancer)

no longer functions as intended

proliferative

grows uncontrollably, does not respond to stop signals

growth factors that cause cancer development

insulin and estrogen

insulin (cancer)

stimulates the growth of cells and suppresses apoptosis

estrogen

stimulates the growth of breast tissue, in postmenopausal women it stimulates the growth of breast tumours, it circulates in the blood either bound to a sex hormone binding globulin or in free form

estrogen bound to sex hormone binding globulin (SHBG)

less bioavailable so stimulates less cell growth

free estrogen

not bound to anything so more bioavailable and stimulates cell growth more

weight stigmatization

refers to negative attitudes, mistreatment and discrimination based on weight status, particularly negative attitudes toward the obese