chapter 4: carbs, sugar, starch and fiber

what is carb abbreviated as

CHO cuz

Composed of
– Carbon
– Hydrogen
– Oxygen

3 types of carbs

monosaccharides - simple

disaccharides - simple

polysaccharides - complex

list of monosaccharides

Glucose, fructose, and galactose

list of disaccharides

• maltose, sucrose and lactose

list of polysaccharides

• starches and fibers

• more complex

• contain many glucose units

glucose

AKA blood sugar

-essential energy source

• part of every disaccharide

• monosaccharide

fructose

• monosaccharide

• sweetest of the sugars

galactose

• only in a few foods (milk)

• monosaccharide

disaccharides list

• maltose

• sucrose

• lactose

maltose

• disaccharide

• made of 2 glucose units

sucrose

• disaccharide

• made of glucose and fructose

lactose

made of glucose and galactose

• disaccharide

condensation

• links 2 monosaccharides together

• releases water

hydrolysis

Breaks a disaccharide in two
– Adds the water “back” to break the bond

condensation vs hydrolysis image

specific types of polysaccharides list

• glycogen

• starch

• dietary fiber

glycogen

• animal version of polysaccharide

• storage form of energy (from CHO in the body)

• polysaccharide

• contains hundreds of glucose units in highly branched chains

how many grams of glycogen are stored with how many grams of water

• 1 gram of glycogen is stored with 3 grams of water.

Starch + 2 types of starch

• (plant version of polysaccharide)

• Amylose linear chain of glucose molecules linked end-to-end.-

• —> may resist breakdown and become resistant starch

• —→hundreds of glucose molecules in unbranched chains

• Amylopectin is a much larger molecule with numerous branches of short
  chains of glucose molecules linked to a main chain like the branches

• —→ hundreds of glucose molecules in occasionally branched chains

dietary fiber

(plant polysaccharide that we cannot
break down in our digestive tracts)

• differ from starches cuz we do not have enzymes to break it down

• contain soluble and insoluble fibers

• —→ soluble fibers dissolve in water, slow gastric emptying time (make u fuller for longer), are fermentable (gut microbes ferment solu fiber and produce short chain fatty acids)

• —→ insoluble fibers provide bulk and normalise bowel function

phytic aciid

not a fiber, but associated with fiber
– Binds minerals
– Antioxidant

functional fibers

• is a polysaccharide / dietary fiber

• e.g. (inulin, cellulose)
  • Added to foods
  • Used as supplements (psyllium

resistant starch

• polysaccharide/ dietary fiber

• e.g. chilled amylose

how an enzyme works

what enzyme digests what carbs

• Lactase digests Lactose
• Amylase digests ___ amylose/amylopectin (starch)
• Maltase digests ____ Maltose
• Sucrase digests ____ Sucrose
• Beano® digests ____ Fiber
• Lactaid® digests ____ Lactose

digestion of carbs

• goal is to get glucose for absorption and use

• digestion of CHO is hydrolysis via enzymes

• mouth mechanically breaks down food and mixes with saliva which has salivary amylase that breaks down carbs with enzymes

• stomach has stomach acid that has protein digesting enzymes

• small intestine has pancreatic amylase

• —> specific disaccharide enzymes: maltase, sucrase, lactase

• large intestine is where soluble fiber is fermented and insoluble fiber holds liquid and is bulk waste

summary of carbohydrate digestion

absorption of carbs

• most carb absorption (put carbs in bloodstream) happens in small intestine with other nutrients too

• glucose and galactose absorbed by active transport

• fructose is absorbed by facilitated diffusion

• liver:

• —→ facilitates conv of fructose and galactose, directs glucose, and stores glucose as glycogen if not need now

lactose intolerance

• highest lactase activity is immediately after birth, and declines with age

• prevalence determinesd by genetics

• to help, make dietary changes

• —→ manage dairy consumption by choosing fermented milk products like kefir or yoghurt, getting products with laactose alr digested like lactaid, having an individualized diet

• avoidance of lactose can result in riboflavin, vit D, calcium + protein deficiencies

how is glucose stored as glycogen

Liver storage
 Condensation into glycogen
 Hydrolysis of glycogen for rdelease of glucose when
needed
– Muscle storage
 Selfishly hoards glycogen

glucose is preferred source for what cells

Preferred source for brain, nerve cells, and developing red
blood cells

but if not available, can use protein as fuel

how is glucose made from protein

• Amino acid conversion (“Glucogenic AAs”)
  – Gluconeogenesis (Gluco = Glucose; Neo =
  New; Genesis = making)
  – Nitrogen is waste product

how many grams of carb per day needed to spare protein and prevent ketosis

• 50- 100 g carb per day

what happens if inadequate supply of carb

• fat metabolism shifts

• body breaks down fat for energy and forms ketones (bodies)

• ketosis disripts acid base balance

what happens to extra glucose (2 step)

• Extra glucose first makes glycogen (stored
  form of glucose “body starch”)
  • Remaining extra glucose made into fat

  
  

what does insulin do

• moves glucose from bloon INTO cells

• helps maintain blood glucose homeostasis

what does glucagon and epinephrine do

• brings glucose out from storage (from liver glycogen)

• helps maintain blood glucose homeostasis

how is a steady supply of blood glucose maintained in blood stream

• Intestines – food (use as you go)

• – Liver – glycogen (use from stores
  between meals)

are things ever digested in pancreas

NO

insulins response in more detail

• how high insulin surge is in the body influences how the body stores or uses its glucose

• glycemic effect is how quickly and how much a food raises your blood sugar levels - factors that influence this is glycemic index and body weight and other foods

insulin resistance

• starts 10 years before diabetes dx

• most often caused by obesity (visceral fat)

• insufficient sleep (less than 6 hrs) makes it worse

• takes more insulin to deliver the glucose

muscles share glycogen…

locally

liver shares glycogen…

to all body parts

Feedback loops for glucagon and insulin

what is the glycemic index

• a measure of how quickly or slowly a carb food is digested and increases blood glucose levels

higher glycemic index carbs..

increase blood glucose levels more quickly

lower glycemic index carbs

increase blood glucose levels more slowly.

what is the glycemic response

• speed of glucose absorption, how it rises, and the rate of return to normal levels

low glycemic response vs high glycemic response

• low glycemic response are long acting - timed release

• high glycemic response are fast sugar surge

honey has ___ grams per tso whereas sucrose has __ grams per tsp sucrose

honey - 6 grams per tsp

sucrose - 4 grams per tsp

health effects and recommended intakes of sugars

• bacteria ferment sugars producing acid 20-30 min after each exposure

• Food factors associated with tooth decay
   Time of food in mouth
   Sticky foods
   Frequency of sugar consumption
   Acidity of liquids
  – Food choices (natural sugars, fiber, protein, eating occasionally
  rather than continuously)
  – Factors associated with tooth decay
   Poor oral hygiene
   Saliva factors
   Strep Mutans (does not like Xylitol)e Xylitol)

what are sugar alcohols and what do they do, what problems can come cuz of them!

Sugar Alcohols
• What they are
– Reduced calorie sweeteners 2 – 2.6 cal/gram
– Naturally occur in fruits & vegetables
– Known as “nutritive sweeteners”
• What they do
– Low glycemic response (enter bloodstream
more slowly)
– Do not contribute to dental caries
– Xylitol reduces strep mutans in saliva & plaque
• Problems
– Excessive amounts can cause gas, diarrhea,
and bloating

dietary guidelines for Americans

• limit added sugars to 10% of total energy

WHO and FAO recs for added sugar

• less than 10% of total energy, so 5-10%

American Heart Association added sugar recs

• average is 6%

• limit to 100 cal for women (roughly 5% of total daily calories intake)

• limit to 150 cal for men (roughly 7% of daily calories intake)

DV for added sugar

50 g

DRI for added sugars

• less than 25% of day’s total energy

non nutritive sweeteners

Artificial sweeteners
– Non-nutritive sweeteners
– Large doses and adverse effects
– May not affect weight
• Stevia – an herbal product
– Generally recognized as safe (GRAS)
• Saccharin
– Discovered by accident

soluble fiber

Soluble Fiber
• Soluble fiber produces a thick, viscous liquid
similar to honey in gastrointestinal fluid
• Soluble fiber is readily metabolized by gut
bacteria, which convert much of it into small
molecules called short-chain fatty acids
(SCFA)
• The cells lining the colon obtain about 60-70% of their energy from SCFA
70% of their energy from SCFA

viscous, soluble more fermentable fibers

• gums

• pectins

• psyllium

• some hemicellulose

nonviscous, insoluble, less fermentable

• cellulose

• lignins

• resistant starch

• hemicellulose

excessive fiber intakes

• insufficient energy or nutrient needs

• – Abdominal discomfort, gas, diarrhea
  – GI obstruction
  – Nutrient absorption (phytates bind)
  – Dietary goals
   Balance, moderation, and variety

Health Effects and Recommended Intakes of
Starch and Fibers

Heart disease
– Whole grains (3 is Key)
 Sources
 Intact are best
– Soluble fibers (absorb liquid)
 Oat bran, barley, legumes
 Cellulose, Hemi-cellulose, pectins, gums
 Have cholesterol-lowering effect
• Diabetes
– High-fiber foods
– Unprocessed foods

recommended intakes of carb and fiber

Carbohydrates
– AMDR: 45 to 65% of energy requirement
– RDA: 130 grams per day
– DV: 275 grams per day (55% of 2000 cal)
• Fiber
– DV: 28 grams per 2000 kcalories
– DRI: 14 grams per 1000 kcalories (28 gm/2000
kcal)
– No UL
• Protein sparing: 50 – 100 g CHO
Revised!