Carbohydrate Digestion Flashcards
3 Functions of carbs?
1) supplies energy (from glucose)
2) Protein sparing
3) prevents ketosis
Main energy source and how is this stored?
Glucose, stored as glycogen in the liver and muscle
How much energy of the NZ diet do carbohydrates produce
40-60%
the link between carbs and many ethnicities?
carbs form a staple food for majority of ethnicities around the world.
asian = rice
european = wheat/potatoes
Complex carbs and simple sugars eventually end up as
Glucose
Types of complex carbohydrates
1) starches: potatoes, bread, rice (glucose)
2) Dietary Fibres:
- INSOLUBLE (bran)
- SOUBLE (lentils, beans)
Types of simple carbohydrates?
Sugars: (glucose)
1) Dissacharides - sucrose, maltose, lactose
2) monosaccharides - fructose, glucose, galactose
compounds that make up carbs
aldehydes + ketones
Types of monosaccharides
glucose, fructose, galactose
Galactose
found in milk / dairy products
Fructose
found in veges + fruit
Types of disaccharides and what makes the
Maltose= glucose + glucose Sucrose= glucose + fructose Lactose = glucose + galactose
maltose is for
fermentation and alcohol production
Sucrose is found in
table sugar + processed foods
What are polysaccharides. What is their purpose?
A chain of two or more monosaccharides. Chain may be branched (amylose) or branched (amylopectin + glycogen)
They function as food storage as glycogen
Amylose and amylopectin are…?
Both storage polysaccharides of plants. Made up of glucose polymers, they are starches (not water soluble)
-found in cereals, grains, root veges, legumes
Features of glycogen (liver & skeletal muscle)
- storage form of glucose
- 12-14 hrs worth stores
- Provides a rapid release of energy when needed
- liver releases first (bloodglucose control)
Non-starch polysaccharides are, and what are the types?
polysaccharies with glucose links that can’t be broken (so can’t be digested) = “NSP dietary fibre”
-give very little E
1) SOLUBLE FIBRE: dissolves in water, forms gels, easily digested by bacteria (fermented)
2) INSOLUBLE FIBRE: doesn’t dissolve or form gels, not easily fermented
Digestion of Carbs in the mouth?
S: salivary glands secrete saliva into the mouth. Moistens food, amylase hydrolyses starch > small PS
DF: mechanical action of the mouth crushes/mixes DF with saliva for swallowing
Digestion of carbs in the stomach?
S: stomach acid inactivates salivary enzymes
DF: DF not digested, delays gastric emptying
Digestion of starch carbs in SI?
S: chyme stimulates pancreas to release amylase. This breaks starch down > small PS
PS go to surface of micro villi
DS enzymes on surface of SI cells hydrolyse DS into MS that can now be absorbed
(*DS enzymes specific to specific DS)
Digestion of Dietary Fibre in SI and LI
SI: DF is not digested, delays absorption
LI: bacterial enzymes digest DF into SCFA, gas
The steps of monosaccharide absorption?
takes place mainly in the SI
1) MS enter capillaries of the intestinal villi
- Glucose & galactose via AT of GLUT-1 transport protein
- Fructose via facilitated diffusion
2) MS travel to liver via Hepatic portal vein
3) in the liver, galactose & fructose > glucose
4) Glucose now available to be used to either control blood sugar or be stored as glycogen
Why are people concerned for those who consume excessive amounts of fructose
That they may have issues with excess storage of fructose within the liver > fatty liver
What happens when storage of carbs runs out?
body protein > glucose
fat stores > ketones (ketosis)
Recommended servings of carbs a day
Preschoolers = 4 children = 5 adults = 6
Difference between intrinsic and free sugars?
Intrinsic found in fruit & vege (lactose, fructose) Free sugar (sucrose) added by manufacturers, we need to reduce, 50% of NZ intake
Insoluble fibre?
provides mass to faeces. Fibres attract water ensure the stools are large and soft
Soluble fibre
- Binds w FAs
- prolong emptying (fuller for longer)
- lowers cholesterol + LDL cholesterol
- fermented by bacteria > SCFAs that feed gut enterocytes, ensure appropriate DNA methylation.
- regulates Blood sugar
What does your microbiota do?
How do we get it?
What happens if this changes?
Live synergistically, thrive off carbs/fibre (only thing they can proliferate off)
Unique to us, born with, also vaginal delivery and breast millk affects
Changes with: bad diet, illness, AB
Recommended intakes of carbs
45-65% carbs
of this 10% simple sugars
15% > 5%
What happens when you have a high glycaemic Diet?
1) eat food with HGI, is absorbed very quickly, we get a high peak of blood glucose and insulin (to decrease this)
2) then as your blood glucose & insulin rapidly drops > hyperglycaemic effect > hunger
3) snack again… cycle repeats
Why are people encouraged to eat things with a LGI?
creates a more plateau effect (not peaks), fully for longer
Symptoms of lactose malabsorption?
bloating, abdominal discomfort, diarrhoea
as sugar overload disrupts the osmotic balance of LI
Primary Lactase deficiency? Management?
Genetically predisposed
Managed by: removing milk products from diet
OR taking lactase enzyme tablets with your milk product
secondary lactase deficiency?
Due to a condition (gastroenteritis, celiac that destrys villi in SI)»_space; lactose malabsorption
Managed by: initially removing milk products, slowly introducing them back
