Download Lecture 3b powerpoint

Lecture 3b- 26 Sept. 2016
CARBOHYDRATES II
Overview of lecture 3b
Carbohydrates
-blood glucose homeostasis
-functions of carbohydrates
essential or not?
-fad diets
BLOOD GLUCOSE HOMEOSTASIS P. 106-109
Maintaining blood glucose at normal levels is important
-too low-dizzy and weak
-too high-fatigued, confused and difficulty breathing
Regulating hormones - insulin and glucagon
Balancing in normal range - insulin and glucagon
Blood glucose homeostasis continued
Falling outside normal range
-diet does not regulate blood sugar-the body does
-diabetes-types 1 and 2 and gestational diabetes-elevated blood glucose
-type 1 diabetes -autoimmune attack on pancreatic beta cells
-used to be called insulin dependent diabetes mellitus or
juvenile diabetes
-no cure at the moment
-type 2 diabetes -insulin resistance followed by beta cell failure
-used to be called-non-insulin dependent diabetes
mellitus(NIDDM) or adult onset diabetes
-no cure at the moment
-gestational diabetes (GDM) -insulin resistance in pregnancy due to excessive
weight gain
-resolves with medical management
-greater risk of type 2 diabetes later on for mum
and post-partum child who experienced in
utero GDM
-hypoglycemia-low blood glucose from too much insulin or not enough
to eat
Blood glucose homeostasis continued
Falling outside normal range continued
-but dietary modifications important-before and after type 2 diabetes, GDM and hypoglycemia sets in
-for type 2 diabetes and GDM avoid uneccessary weight gain by
dietary change-low fat and rich in complex carbohydrate and
fibre
-for hypoglycemia-get enough to eat
Blood glucose and diet p. 108-9
glycaemia-blood glucose
glycaemic index of food-ability to provoke a blood glucose response
- effects blood sugar rise
-high glycaemic index foods (eg white bread) causes rapid rise
in blood glucose followed by quicker drop in blood
glucose
-lower glycaemic foods (eg whole grain bread) - causes less
rapid rise in blood glucose followed by slower drop in
blood glucose - may reduce chances of getting or
worsening type 2 diabetes
-effect of food on blood glucose-if have slow absorption get
modest rise in blood glucose and smooth decrease of
blood glucose
Blood glucose and diet continued
P.108-9
-blood glucose dependent on whether carbohydrate eaten alone or as
part of a mixed meal
-eating small meals often is same as low glycemic index-why?
Blood glucose and diet continued
page 108
-however, glycemic index is controversial
- inadequate science?
- determined for relatively few foods
- when determined it is based on average of multiple
tests with a great deal of variability
Blood glucose and diet continued
Fad diets
-no apples or oranges but bacon and eggs alright-this is not
good why?
Carbohydrates - essential or not?
yes- why?
Healthy roles for carbohydrates
1) neural function
2) give structure to molecules
3) metabolically
4) impact on nutrient absorption
Carbohydrate functions- healthy
Neural function
• brain and nerves really only set up
to use glucose
• lipids/proteins cannot be used
Carbohydrate functions-healthy continued
give structure to molecules
carbohydrate
e.g. glycogen
disaccharides
oligosaccharides
non-carbohydrate
e.g. some proteins (i.e. glycoproteins)
Carbohydrate functions-healthy continued
metabolically
-energy-heat/fuel
-sparing protein
-burning fat
Carbohydrate functions healthy continued
metabolically continued
make other compounds
- glycogen
- fat
- protein (non-essential amino acids)
- DNA/RNA
Carbohydrate functions-healthy continued
Impact on nutrient handling
• non-absorbable oligosaccharides impair carbohydrase
activity
• starch granules exposed to moist heat and then cooling are
less dense and hence less available to enzyme action
Unhealthy roles for carbohydrate
glycation (glycosylation) of proteins
proteins-albumin
-hemoglobin
lipoproteins
blood vessels
Unhealthy roles for carbohydrate glycation
(glycosylation) of proteins continued
albumin glycation or glycosylation
can cause tissue breakdown via stimulating chemical messengers
Unhealthy roles for carbohydrate glycation
(glycosylation) of proteins continued
Haemoglobin
may set up a chemical reaction that leads to blood vessel breakdown
Unhealthy roles for carbohydrate-glycation
(glycosylation) of proteins continued
Lipoproteins

low good cholesterol

higher bad cholesterol
Unhealthy roles for carbohydrate glycation
(glycosylation) of proteins continued
Blood vessels
glucose itself binds to protein in blood vessels-leaky
Next lecture - carbohydrates in health and disease
Influence of:
• the diet
• nutraceuticals
• functional foods