Carbohydrates Flashcards
carbohydrates role
provide primary source of energy we need to fuel bodily functions
carbohydrate types
simple and complex
carbohydrate negatives
excess consumption specifically of refined carbs are major contributing factor in diseases and premature aging
refined carbs
stripped of fiber, phytochemical, vitamin, and trace elements
too many simple sugars can be harmful to blood sugar control
obesity, heart disease, types of cancer
sweeteners
more than half of carbs in US are simple sugars as sweeteners
sugar, corn sweeteners, honey, maple syrup, other syrups
high fructose corn syrup
increase directly related to overall sugar intake increase
no more fracture in HFCS than sucrose
sweet and less expensive than sucrose
simple sugars
monosaccharide or disaccharide
principal monosaccharides that occur in foods
glucose and fructose
main disaccharides that occur in food
sucrose/white sugar
maltose
lactose
sucrose is comprised of
one glucose and one fructose
maltose is composed of
two glucose
lactose is composed of
one glucose and one galactose
glucose
monosaccharide
not as sweet as fructose and sucrose
fruits, honey, sweet corn, root vegetables
primary repeating sugar unit of most complex carbs (starches)
Fructose
monosaccharide
fruit sugar, maple syrup, honey
very sweet
must first be converted to glucose within the liver
Sucrose
disaccharide
common table sugar
processed foods & some fruits
broken down in the small intestine into constituent sugars (glucose is primary form that enters bloodstream)
Maltose
disaccharide
malted grain products and syrups from grains like barley and sorghum
broken down in the small intestine into constituent sugars (glucose is primary form that enters bloodstream)
Lactose
disaccharide
sugar found in milk
humans have enzyme lactase to digest lactose as infants but later lose this enzyme; by 4 most is gone
some groups like African Americans no lactase = lactose intolerance
lactase can be supplemented for occasional consumption
broken down in the small intestine into constituent sugars (glucose is primary form that enters bloodstream)
complex carbs
starches
simple sugars joined together by chemical bonds
the more chains and branches = more complex
the more complex a carb is…
the more slowly it is broken down
breaks down into simple sugars slowly, better blood sugar control
health benefits of complex carbs including high-fiber foods are…
good for heart disease, types of cancer, diabetes
Glycemic index
provides a numerical value that expresses the rise of blood glucose after eating a particular food
How to compute glycemic index
old way = first standard
new way = starch standard
First standard of GI
based on rise in blood sugar seen with the ingestion of glucose which was given a value of 100
starch standard of GI
a 50g portion of white bread made using refined flour is given the value of 100
white bread is new GI standard because…
glycemic response to white bread is more reliable than response to glucose
glucose attracts water (osmolarity) that can delay gastric emptying and misrepresent insulin response
white bread stimulates more insulin activity than glucose
glycemic index ranges
ranges from 20 for fructose and whole barley to about 98 for a baked potato
insulin response to carb containing foods is imliar to the rise in blood sugar
Glycemic load
takes GI into affect ,along with amount of carb in the food, to give more complete picture of foods affect on blood sugar levels
Dietary fiber
components of the plant cell wall as well as indigestible residues
composition of plant cell wall
varies according to species of plant
in general: 35% insoluble fiber 45% soluble fiber 15% lignans 3% protein 2% ash
Fiber supplements disadvantage
dietary fiber is a complex of the constituents, so supplements can’t substitute for a diet rich in high-fiber foods
Cellulose
insoluble fiber
can’t be digested by humans, but partially digested by beneficial microflora in the gut (their primary food source)
natural fermentation occurs in the colon, leads to degradation of about 50% of cellulose- is important source of short-chain fatty acids that nourish intestinal cells
wheat bran
best example of insoluble fiber
rich in cellulose
ability to bind water
effect of increasing fecal size and weight, promoting regular bowel movements
cellulose plant part
principal plan wall component
cellulose physiological effect
increases fecal weight and size
insoluble fiber
not broken down by water
soluble fiber
majority of fibers in most plan cell walls
broken down by water
most beneficial effects
types of soluble fiber
hemicelluloses, gums, mucilages, pectin, algal polysaccharides
hemicelluloses
found in oat bran, guar gum
increases fecal weight (by increase hydration of stool) and size, binds bile acids
plant = plant cell walls
directly bind cholesterol in gut preventing absorption
hemicelluloses in the gut
bacteria in gut digest, increase beneficial bacteria and create SCFA- colon cells use as fuel and decrease cholesterol
Gums
found within inner layer (endosperm) of grains, legumes, nuts, seeds
karaya, locust bean, tragacanth, gum Arabic
some of most potent cholesterol-lowering agents of the gel-forming fibers
Gums physiological effect
bulk laxative
Mucilage
endosperm of plant seeds
legumes, psyllium, konjac root, slippery elm bark, marshmallow root
Guar gum
technically a mucilage
found in most legumes (beans), most widely studied plant mucilage
stabilizing, thickening, film-forming agent in cheese, dressings, ice cream, soups, toothpaste, pharmaceutical jelly, skin cream, tablets, laxative
mucilage benefit
reduce fasting and after-meal glucose and insulin levels in both health and diabetic subjects
decreased body weight and hunger ratings when taken with meals by obese subjects
pectins
all plant cell walls and in outer skin and rind of fruits and vegetables
pectin foods
rind of an orange = 30% pectin
apple peel = 15%
onion skin= 12%
lowers cholesterol by binding cholesterol and bile acids in the gut and promoting their excretion
mucilage physiological effect
hydrocolloids bind cholesterol and delay gastric emptying, chelate out heavy metals
pectin physiological effect
hydrocolloids bind cholesterol and delay gastric emptying, chelate out heavy metals
pectin & cancer
modified citrus pectin reduce risk of metastasis- spread of cancer cells from one tumor to other sites in body
algal polysaccharides
seaweed gums derived form brown seaweeds like alginates, red seaweeds like agar and carrageenan
alginates
form insoluble cells that are used as emulsifiers, thickeners, and binders in food production
agar
forms a gel that is soluble in hot water, but not cld water
used as a culture medium for microbes as well as stabilizer in many foods
carrageenan
can be broken into components that do and do not form gels
used in foods to thicken and create smooth texture
lignans
compounds found in high-fiber foods
anticancer, antibacterial, antifungal, antiviral activity
changed by gut flora into enterolactone and enterodiol, protective against cancer (mainly breast cancer)
increase production of sex hormone-binding globulin- regulates estrogen levels by escorting excess estrogen from the body
lignan foods
flaxseeds are most abundant source
others- seeds, grains, legumes
inositol
unofficial member of B vitamins
primary component of cell membranes and with phosphate groups attached acts as an important regulator of cell division
inositol benefits
not essential to human diet but supplementation can benefit depression, panic attacks, and diabetes
inositol is required for the proper action of…
several brain neurotransmitters, including serotonin and acetylcholine
inositol and depression
thought that a reduction of brain inositol levels may induce depression
major source of inositol
found in nature as inositol hexaphosphate- component of fiber from whole grains and legumes and not a fiber class on its own
fructooligosaccharides (FOS)
fiber component found in many vegetables
consist of short gains of fructose molecules
FOS example
inulin- found in artichoke, burdock, chicory, dandelion root, leeks, onion, asparagus
only partially digested by humans
undigested portion serves as food for friendly bacteria
physiological effects of dietary fiber
stool weight and transit time
digestion
lipid metabolism
SCFA
intestinal bacterial flora
Fiber benefit- stool weight and transit time
treatment for constipation or diarrhea- normalizes bowel movements
water-insoluble fibers such as cellulose
transit time greatly reduced on high fiber diet
high fiber diet amount, transit time, and stool size
high fiber = 100-170g/day
30 hr transit time
500g fecal weight
low fiber = 20g/day
48hr transit time
100g fecal weight
risks of slow stool transit time
more time in intestinal tract = more exposure to various cancer-causing compounds in intestines
transit time related to stool weight and size
larger, bulkier stool passes through colon easier- less pressure needed for defection = less strain = avoids ballooning effect that creates diverticulitis (sacs or pouches of intestinal tract)
diverticulitis
when diverticuli become lodged with feces, cause inflammation
fiber & digestion
slows gastric emptying so food is released more slowly into small intestine and blood glucose levels rise more gradually
pancreatic enzyme secretion and activity increase to fiber
fiber & mineral absorption
large amounts of dietary fiber (more than 50g) may impair mineral absorption
supplemental fiber of insoluble fiber (more than 5g) especially wheat bran may cause mineral deficiencies
usual levels or supplement with soluble doesn’t interfere
lipid metabolism
water-soluble cells and mucilaginous fibers (oat bran, guar gum, pectin) can lower serum cholesterol and triglyceride levels by increasing fecal excretion and preventing manufacture in the liver
insoluble fibers like wheat bran have less effect in reducing serum lipid levels
SCFA
produced by fermentation of dietary fiber by intestinal flora
acetic, propionic, butyric
energy production, lower elevated cholesterol, energy for colon cells, anticancer
fibers most effective for increasing SCFAs
pectins, guar gums, legume fibers
intestinal bacterial flora
fiber maintains suitable bacterial flora in colon
low-fiber = overgrowth of endotoxin producing bacteria (bad) and lower lactobacillus (good) and other acid-loving bacteria
SCFAs reduce colon pH= create friendly growth of acid-loving bacteria
heart disease and fiber
diet high in dietary fiber = reduce total cholesterol and triglyceride levels while increasing HDL cholesterol levels
obesity and fiber
dietary fiber prevents obesity by:
increasing amount of chewing, slow down eating
increasing fecal caloric loss
improving blood sugar control
inducing satiety (feeling of fullness)
diabetes and fiber
type 2 most clearly related to inadequate dietary fiber intake
soluble sources significantly better than insoluble for diabetes application
nuts, seeds, fish, poultry, meats & GL
little impact on blood sugar levels
these, especially fats and oils, can lower FI of carb-rich foods by delaying absorption
