Week 3 Flashcards
carbohydrates
- provide energy for brain and NS
- help keep digestive system healthy
- help keep body lean (within energy limits)
indigestible carbs
yield little or no energy
carb-rich foods
- plants (grains, fruits, veggies, legumes)
- milk products (milk, yogurt)
- concentrated sugars (candy, cake)
categories of carbs
- simple carbs
- complex carbs
simple carbs
- monosaccharides - single sugar
- disaccharides - pairs of mono
complex carbs
polysaccharides - chains of mono
3 monosaccharides
- glucose
- fructose
- galactose
- all have same number and kind of atoms arranged in different ways
glucose
- mildly sweet
- essential energy source for body activities
- one of the 2 sugars of every disaccharide
- make up polysaccharides
galactose
component of milk sugar
1. not sweet at all
2. occurs as one of the two single sugars in milk products
3. found occasionally as a single sugar
Ex. fermented milk products (yogurt and aged cheese)
fructose
- intensely sweet - sweetest monosaccharide
- called fruit sugar
- occurs naturally in fruits and honey
high-fructose corn syrup
made from cornstarch that has been treated with an enzyme that converts some of the glucose to the sweeter fructose
3 disaccharides (double sugars)
- lactose
- maltose
- sucrose
- join together by condensation reactions
- split by hydrolysis reactions
lactose
milk sugar
1. glucose + galactose
2. principle carb of milk
3. provides 1/2 kcal in skin milk
maltose
- glucose + glucose
- produced during starch breakdown
- occurs during alcohol fermentation
ex. barley
sucrose
- glucose + fructose
- sweetest of disaccharides
- occurs naturally in fruits, veggies, and grains
table sugar
sucrose refined from beets or sugarcane
brown sugar
white sugar with molasses added
eating sugar
- monosaccharides are absorbed directly into blood
- disaccharides are digested before absorption (split into mono by enzymes)
what is the most used nutrient in the body?
glucose
nutrition facts table and sugar
% DV = natural and artificial sugar combines
why are fruits different from purified sugars like those in candy and soft drinks?
fruits contain:
1. fibre
2. phytochemicals
3. vitamins and minerals
polysaccharides
- starch
- glycogen
- fibre
- made up of many strands of glucose
- known as complex carbs
starch
- storage form of glucose in plants
- long chains of glucose molecules linked
- nutritive: we digest it to glucose
branched starch
amylopectin
unbranched starch
amylose
rich food sources of starch
- grains
- tubers (yams and potatoes)
- legumes (peas and beans)
glycogen
- storage form of glucose in animals
- highly branched glucose chains
- stored in muscle (2/3) and liver (1/3)
why is glycogen made up of highly branched glucose chains?
allows for rapid hydrolysis - surge of glucose
does meat contain a large amount of carbs?
NO
- glycogen breaks down rapidly when the animal is slaughtered
fibre
- found in veggies, fruit, whole grains and legumes
- some provide support and structure to plants (stem, seeds)
- some retain water to protect seeds from drying out
- most as polysaccharides
- prebiotic
fibre and digestion
- human digestive enzymes cannot break the bonds that hold together sugar units of fibre
- most fibres pass through human body without providing energy
- bacteria in the LI can digest fibres to varying degrees by fermenting them
prebiotics
foods that are not digested (fibre) but promote bacterial growth by acting as food for bacteria
soluble fibres
- dissolve in water
- form gels (viscous)
- can be digested by bacteria in human colon
- soften stool
- slow glucose absorption
rich food sources of soluble fibre
- barley
- legumes
- oats
- apples
- citrus fruits
- used as a thickening agent (pectin, gums, psyllium and hemicelluloses)
benefit of soluble fibres
lower risk of chronic disease- decrease cholesterol
insoluble fibres
- do not dissolve in water
- retain their structure and texture even after hours of cooking
- less easily fermented and do not form gels
food sources of insoluble fibres
- outer layers of whole grains
- strings of celery
- cellulose, lignin, resistant starches, hemicelluloses, inulin
benefit of insoluble fibres
- ease elimination
- can alleviate constipation
- speed passage of feces through colon
why are carbs needed
glucose is an important fuel for most body functions
- 45%-65% of daily kcals come from carbs (DRI)
proteins in comparison to carbs
- more expensive
- provide no advantage when used as fuel for the body
- overuse of proteins has potential disadvantages
fats in comparison to carbs
fats are not normally used as fuel by the brain and central nervous system - glucose is
are carbs healthy for body weight?
- carbs are wrongly accused of being “fattening”
- carbs contain fewer calories than fats (fats are most energy dense)
- converting glucose into fat is metabolically costly (requires energy)
complex carbs vs. refined sugars
complex carbs: recommended - contribute to nutrients
refined sugars: displace nutrient-dense foods from diet and contains no other nutrients (empty-calorie foods)
healthy carb diet
- reduce refined sugar to reduce risk of CVD
- include veggies, fruits and whole unrefined grains and legumes
- increased intake of fibre-rich, whole foods
- reduce refined white flour, sugars and some fats associated with heart disease
why are fibre-rich foods recommended?
- supply vitamins, minerals and phytochemicals
- contain little or no fat - low energy density (except nuts)
- maintenance of healthy bowel function
- modulation of blood glucose concentrations
- fibre maintains health body weight
- soluble fibres (apples) have cholesterol-lowering effects
why do complex carb diets protect against heart disease and stroke?
- low in saturated fat, trans fat and cholesterol
- high in fibres, vegetable proteins and phytochemicals
foods rich in viscous fibres
lower blood cholesterol by binding with cholesterol-containing bile and carrying it our with feces
- bile is made in the liver by taking the body cholesterol
blood glucose control
- viscous fibres trap nutrients and delay their transit through digestive tract
- glucose absorption slows, which steady the levels of blood glucose and insulin
- lower glycemic index
maintenance of digestive tract health
fibre and fluid intake play a role in maintaining colon function and preventing and alleviating constipation
1. enlarges and softens stools
2. speeds passage through the intestine
3. easier elimination
constipation
- fibre helps prevent
- large, soft stools ease elimination helping prevent hemorrhoids
- fibre helps prevent compaction of intestinal contents
- fibre stimulates the GI tract muscles so they retain their strength and resist bulging out into pouches (diverticula)
compaction of intestinal contents
could obstruct the appendix and permit bacteria to invade and infect it (appendicitis)
diverticulitis
inflammation of the diverticula
high-fibre diets
lower the rates of colon cancer relative to low-fibre diets
why is a high-fibre diet recommended?
- contains nutrients and phytochemicals
- dilute and speed the removal of cancer-causing agents from the colon
- promote bacterial reproduction, binding nitrogen and carrying it out of the body in feces
- bacteria ferment soluble fibres into short chain fatty acids which may help the colon resist chemical injury leading to cancer
healthy weight management and complex carbs
foods rich in complex carbs tend to be low in fats and added sugars
1. may promote weight loss by providing less energy
2. fibre creates feelings of fullness and delays hunger - swells as it absorbs water
pure fibre compounds
usually not necessary and can be dangerous
- most benefits of fibre come from foods
- too much fibre without enough water can cause constipation
fibre recommendations and intakes
AI: females age 19-50: 25 g/day
AI: females age 51 up: 21 g/day
AI: males age 19-50: 38 g/day
AI males age 51 up: 30 g/day
average intake is about 14-15 g/day
diet with too much fibre
- purified fibre can lead to blocked intestine (wheat bran)
- binders in some fibres act as chelating agents
- too much bulk in the diet can limit food intake and cause both nutrient and energy deficiencies
- fibres remove water from the body: can contribute to dehydration
chelating agents
bind minerals and carry them out of the body
- may limit the absorption of iron, zinc and calcium
bran
largely made out of cellulose
1. protects the grain
2. generally removed by milling