Class 6- Carbs, Sugars, starches, and fibres

sandy Phillips, she. 4

carbohydrates name meaning

carbo (C) + hydrate (h20)= CH2O

why are plants important in relation to carbs?

glucose is..

PREFERRED energy for brain, nerve cells, RBC,

classic monosaccharides (3):

ALL C6H12O6

Fructose= pentagon, founding fruits and honey, the SWEETEST of all sugars

glucose=blood sugar, part of every disaccaride

galactose= naturally in dairy

**Glucose and galactose differ in orientation of OH position**

classic disaccharides (3), how are they formed VS broken

all formed via condensation rain, water molecule is released

all broken via hydrolysis, usually occurs during digestion

maltose= glucose+glucose, eg barley

sucrose= glucose+fructose, eg table sugar

Lactose=glucose+galactose, eg milk

why is fructose special

• metabolized in liver, can make fat in liver itself

• if high intake of added sugar (which is ½ fructose), liver responds by making extra fat —→ results in fatty liver OR can be transported into raise blood lipids and inc fat stores

difference between high fructose corn syrup VS sucrose

Both are frequently approx. 50:50 fructose

and glucose. (Some HFCS has higher level of fructose)

• Sucrose (table sugar) bound like disaccharide

• HFCS separate glucose and fructose molecules

in liquid format

• HFCS intake declining in North America

3 classes of polysaccharides

Glycogen=stored in liver and muscles, highly branched, reserve for energy

starch= storage form of ;glucose for plants’ long branched AND unbranched chains

Fibre= structural part of plants,

What is glycogen?

Liver makes some glucose into glycogen which is stored

in the liver.

• Muscles can also make and store glycogen from glucose.

• Glycogen can be broken down to release glucose when needed

• Liver is “generous” with its glycogen bc glycogen from liver is broken down to glucose, delivered via blood to organ that needs it. Glycogen can sustain needs when a long time

between meals.

• Muscle cells are “greedy”. They use glucose to make and store glycogen for their own use as energy source for the muscle itself. —> they use glycogen they store themselves

how is glycogen stored throughout body?, how long doe sit last

liver= about 1/3 of glycogen stores, readily available for brains, nerves, blood cells

muscles= 2/3 of glycogen stores (300-400g) in body

GLYCOGEN STORES LAST ~1 day

summary of carbohydrates uses in body

How much carbs does DRI and RDA reccomend?

-minimum of 130g

-RDA reflects need of brain, nerves and

blood cells for glucose, and does not meet

most individuals energy needs

-no UL!

what is DRI AMDR for carbs?

45-65% of total cals

what enzymes begins carb digestion?

amylase, makes smaller polysaccharides, maltose

what inactivates salivary enzymes?

stomach acids

what produces amylase (after salivary glands), where is it released?

The pancreas produces an

amylase that is released through

the pancreatic duct into the small

intestine

Then xxx xxxx on

the surface of the small intestinal

cells hydrolyze the disaccharides

into monosaccharides

Then disaccharidase enzymes on

the surface of the small intestinal

cells hydrolyze the disaccharides

into monosaccharides

general steps of monosaccharide absorption

1. monosaccharides enter capillaries of intestinal villi (of small intestine)

2. monosaccharides travel to liver via portal vein

3. in liver, galactose and fructose are converted to glucose

which disaccharides enter xxxx using active vs passive transport?

entering intestinal cells

ACTIVE transport—> glucose & galactose

PASSIVE transport—> facilitated diffusion

• once in the liver, fructose and galactose can be converted into glucose

As blood glucose levels rise/drops, what responds first ?

pancreas

if blood glucose drops, xxx releases yyy

pancreas releases hormone glucagon

if blood glucose rises xxx releases yyy

pancreas releases insulin

does brain store any ‘energy"‘?

yes, brain store some glucose

• acts as Emergency reserve to fuel the brain in severe glucose deprivation

glycogenolysis

breakdown to release glucose

very simple way that insulin works is..

how does body handle excess glucose?

Once the liver and muscles have supplied tissues with needed glucose and stored glycogen to max capacity, then the body burns excess glucose for energy OR converts to fat and stores as fat

pathway of fibre digestion

1. mouth crushes and tears fibre in food and mixes it w saliva to moisten for swallowing

2. stomach, not digested there and DELAYS gastric emptying

3. large intestine, most fibre remain in tact and bacterial enzymes digest fibre

About 1–4 hours after a meal, all the —- and

— have been digested/absorbed. Only the xxx remains

About 1–4 hours after a meal, all the sugars and

starches have been digested/absorbed.

Only the fibres remain. In the colon fibres attract

water, which softens the stool.

bacteria ferment fibre causing gases (3 types) and xxx:

methane, co2, h2, and short-chain fatty acids (acetate, propionate, butyrate)

how are short chain fatty acids used (SCFA)s

can be used by colonic cells for energy

generally, fibre contributes xx cal/gram

1.5-2.5 cal/gram

2 types of fibre, which is more fermented and what are common sources?

– Soluble, viscous, fermentable fibres are often

gummy or add thickness to foods

ex: pectin, gums, legumes, additives like xanthum gum , guar gum

– Insoluble, nonviscous, less fermentable fibres

are often tough, stringy, or gritty in foods

ex: cellulose inver wheat bran,

action of fibre in stomach

• delays gastric emptying

• fullness sensation, satiety

action of fibre in small intestine (soluble vs insoluble)

• not digested by our enzymes

• slows absorption

– better glycemic control

• Soluble - binds bile acids

– ↓ enterohepatic circulation

– ↓ fat, cholesterol and fat sol vitamin

absorption

– ↓ cholesterol levels

• Insoluble - binds cations

– ↓ Fe, Ca, Zn absorption

low vs high fibre diet in relation to cholesterol

what are DRI recommendations of fibre?

AI for fibre is based on caloric energy intake (25g per 2000cal)

– 38 g/day for men

– 25 g/day for women

• No UL (though greatly exceeding the AI or

increasing too quickly could have some

negative consequences)

summary of characteristic , sources, and health effects of fibre

glycemic response definition

extent to which a food raises

blood glucose

glycemic index (GI) definition

scale that ranks a arbohydrate-containing food or drink by how much it raises blood sugar levels after it is consumed

glycemic load (GL) definition

takes into account both the GI and the amount of available carbohydrates in that serving.

how long does juice, simple/refined carbs, vs mixed meals take to consume/digest/absorb

• Juice: 10 – 20 min

• Refined (simple) carbohydrates by itself, ex: plain cooked white rice, pasta or bread: 30 - 60min

• Mixed meals with Carb + Protein/Fat: Protein and fat stay longer in stomach. 2 - 4 hours

what type of factors can affect glycemic index

varies between individual people:

1. Time of day, body size and weight, blood volume, and metabolic rate

2. Amount consumed

3. Depends on how the food is prepared (raw, cooked, cooled, al dente vs well-cooked…)

4. Food combinations in a meal

why is sourdough lower GI?

high resistant starch, low glycemic index

“Sourdough fermentation is the oldest method of dough fermentation and occurs with the help of yeast and lactic acid bacteria. Acetic acid appears to be associated with a delay in gastric emptying. Acid induces interactions between starch and gluten during dough baking and reduces starch availability.”

why is resistant starch beneficial ?

Instead of being fully digested and absorbed by

the time passes through the small intestine, the

resistant starch may arrive in the colon (similar to

fiber in that sense) and ferment there.

• Lower glycemic index.

Examples:

– Raw potato versus cooked.

– Green-tipped or green bananas versus ripe bananas.

– Starch inside seeds.

– Cooked starchy food that is then cooled

why are resistant starches harder to digest?

resistance starch has highly ordered starch structure —> difficult for humans to digest.

• ex: Cooking potatoes weakens the structure,

making it easier for break down and

digestion.

how to calculate starch in food