Carbohydrates

still refer back to lecture

what is the acceptable macronutrient distribution ranges for cabohydrates

45-65% of total calories

how much recommended dietary allowance for carbohydrates

130 g/day for brain fundtion

whole vs refined carb

refined carbs retains energy and carbohydrates of a food but removes most of the other nutrients such as purified carbs flour, sugar, etc. whereas whole are things like whole fruit, grain and vegetables

simplest form of carb

monosaccharides

oligosaccharides vs polysaccharide

oli is 3-10 units of the monosaccharide chain whereas poly is over 10

chain of glucose breakdown to ATP

Glucose -> glycolysis -> Pyruvate -> acetyl Coa -> oxaloacetate -> Citric acid cycle/ Krebs cycle/ TCA cycle -> NADH, succinate ->Electron transport chain -> ATP

how is does the availability of carb control metabolism

if carb is available oxaloacetate is present as this is synthesized in the Krebs cycle where glucose is further broken down into ATP, and Acetyl-CoA form fatty acid oxidation has oxaloacetate to combine with in the TCA cycle. however if there is no carb available, oxaloacetate is minimal, and the liver would use the Acetyl-CoA instead to make ketone for the brain

what is GLUT 1

found in the blood, blood brain barrier, and to a lesser extent in the heart. this is insulin-independent where it is always on and does not get modulated by the presence or absence of insulin

what is GLUT 2

found in the liver, pancreas and small intestine. it is insulin independent, high Km (amount of substrate needed to have an attraction) and low affinity

what is GLUT 3

found in the brain, neurons and sperm. insulin-independent and low Km (low amount of substrate needed to have attractions due to high affinity) with high affinity

what is GLUT 4

found in the skeletal muscles, adipose tissue, and heart. insulin-dependent with moderate Km and affinity

regulation of high blood glucose

• beta cell in pancreas sense high blood glucose → release insulin

• insulin signals target cells such as skeletal muscle and liver to uptake glucose and store it as glycogen

• as this is done → decrease blood glucose → sensed by beta cells → stop insulin release

regulation of low blood glucose

• alpha cells in the pancreas sense low blood glucose → release glucagon

• glucagon signals its target cells to breakdown glycogen and release glucose

• increase i blood glucose levels will make alpha cells stop releasing glucagon

what is glycemic response

is the effect of a food on blood glucose, this can be impacted by carbohydrate content of food and composition (simple and complex), amount of protein, fat, fibre included in meal and activity level

what is a glycemic index

ranking systems that communicates the ability for a food to increase our blood sugar, with glucose typically given as a 100 for reference. eg, high glycemic index = bigger increase in our blood sugar

what is glycemic load

this combines a food’s GI with the amount of carbohydrates in a serving of food= estimates rate and magnitude of blood sugar increase, and the amount of carbohydrate in the food is multiplied by glycemic index

what is diabetes mellitus

is an endocrine disorder that impacts >460 million people, it is characterized by sustained high blood glucose levels

what happens in type 1 diabetes

this is caused by autoimmune destruction of beta cells in the pancreas, hence signal to uptake glucose is not sent to effectors

treatment of type 1 diabetes

exogenous insulin to replace the critical role of the beta cells in the body

what is type 2 diabetes

caused by insulin resistance in target cells (insulin stimulation does not cause sufficient glucose uptake). the feedback loop exist but it is weak, hence effectors does not respond to signal

treatment of type 2 diabetes

include exogenous insulin, medications to increase insulin sensitivity or secretion or other effects, lifestyle changes including ozempic

significance of ozempic

it is a more stable version of the hormone GLP-1 which enhances insulin secretion by activating an alternative pathway

population high risk for DM

First nations

what are long-term complications of diabetes

constant exposure to high levels of blood glucose causes biochemical changes such as

• glycation of proteins (advanced glycation endproducts (AGE) formation, this damages vasculature, leading to more diseases)

• conversion of glucose into other potentially toxic molecules (polyol pathway)

• increased oxidative stress

• changes in gene expression (insulin as growth factor)

what are the carb recommendations in Canada

• WHO recommends that no more than 10% of calories come from free sugars (sugars added during processing)

• Canada’s food guide recommends more unrefined carbohydrates- whole grains, fruits, vegetables and legumes

risk of too much sugar

• increased risk of T2DM

• increased risk of mortality, primarily through cardiovascular diseases

pros of decreased sugar intake

substantial decrease in the incidence of T2DM, cardiovascular disease and mortality

where to we get most of our carb

sugar and fibre

what is the difference in whole grains vs refined grains

• refined grains only contain the endosperm which are starch and some protein

• whole grains contain bran (fibre and vitamins), germ (vegetable oils an vitamin E) and endosperm (starch and some protein)

does fibre have an enzyme that breaks it down

no, fibre consist of polysaccharides that cannot be digested because we lack enzymes to break it down

soluble vs insoluble fibre

• soluble fibre forms a gelatinous solution with water in the intestine and can be partly digested in large intestine by bacteria

• insoluble fibre does not dissolve in water and are excreted whole

what are functional fibre

is added to processed food for nutritional benefit; soluble or insoluble

function of fibre

fibre helps to slow nutrient absorptionGI tracts contents are diluted by soluble fibre making it more difficult for enzymes to interact with the food resulting in slower digestion and lots of absorption of nutrients in the small intestine

fibre effect on cholesterol and bile salts

dietary fibre helps to lower total cholesterol by preventing their reabsorption in the intestine, and by forcing the liver to remove cholesterol from the blood (to synthesize bile salts)

fibre impact on health

greater quantities of fibre in the diet slow (increase) absorption time but overall speed up (decrease) transit time as fibre slows movement through small intestine and increases movement through large intestine. allowing stool weight to be higher and able to get rid of waster products quickly and effectively

pros of fibre intake

higher fibre diets have been correlated with lower rate of colon cancer, due to faster transit time decreasing contact with toxins

cons of lots of fibre intake

high fibre diet allow faster transit throughout the GI tract that excess pressure can cause the colon wall to bulge out, forming pouches called diverticula. and once fecal matter collects in these pouches, it may case pain, inflammation, infection = diverticulitis