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
endosperm
largely starch grains embedded in a protein matrix
- used in refined flour
germ
part where new grain develops
1. majority of fat in grains are located here
2. often left out of processing to avoid rancidity
modern milling
- removes germ and bran - whiter, smoother-textured flour increasing starch content and lowering fibre content
- white bread meant a loss of nutrients
digestion and absorption of carbs
must be broken down into monosaccharides to obtain glucose
where does starch digestion begin?
the mouth
- then resumes in the small intestine
starch digestion
- via salivary amylase (in saliva)
- starch becomes deactivated by stomach acid
- digestive enzymes found in stomach work best in acidic environments
- pancreatic enzymes split starch into smaller polysaccharides an disaccharides (SI)
- intestinal enzymes split these into monosaccharides (SI)
starch found in refined grains
rapidly broken down into glucose which is then absorbed
resistant starch
behaves like fibre
1. may be digested slowly
2. most remains intact until the bacteria of the colon break it down
3. sometimes classified as insoluble fibre
food sources of resistant starch
- raw potatoes
- unripe bananas
- inside broken husks of swallowed seeds
digestion and absorption of sugars
- digestible carbs are split into monosaccharides before they are absorbed
- pancreatic enzymes split starch into disaccharides
- these are then split by enzymes attached to cells lining SI
ex. lactase, sucrase and maltase
what happens to sugars absorbed in the bloodstream?
the sugars travel to the liver
sugars in the liver
- fructose and galactose are converted to glucose
- circulatory system transports glucose and other products to cells
- liver and muscle cells may store glucose as glycogen
- all cells may use glucose for energy
digestion and absorption of fibres
- many fibres are fermented by intestinal bacteria
- odourous gases are a bi-product
when increasing fibre, how may gas production be minimized?
starting with small servings and then gradually increase serving sizes
why do some people have trouble digesting milk?
- some people produce less lactase
- ability to produce lactase tends to decline with age
- lactase deficiency may also occur because of damage to intestinal villi due to disease, malnutrition, medications or prolonged diarrhea
lactose intolerance
inability to digest lactose
- intestinal bacteria ferment the undigested lactose producing gas and intestinal irritants
severity of lactose intolerant is overestimated
- many can tolerate 1-2 cups of milk a day
- can tolerate lactose-reduced milk
- yogurt and aged cheeses are tolerated
- hard cheese is very low lactose
***not tolerating any lactose at all is very rare
what may increase lactose tolerance?
drinking milk with other foods
- slow the transit time of milk through the digestive tract
milk allergy
allergic reaction to protein in milk
- cannot tolerate any milk products
- must find nondairy calcium sources of calcium
how is glucose released as energy
glycolysis and krebs cycle
DRI carbs recommendations
the minimum intake to feed the brain and reduce ketosis is 130 grams a day for adult average brain
- more is recommended to maintain health and glycogen stores
below healthy minimum of carbs
- body fat cannot be converted into glucose to feed the brain
- the body uses protein to make glucose (gluconeogenesis)
- fat fragments usually combine with a compound derived from glucose before being used for energy
gluconeogenesis
diverting protein from critical functions of its own
- carbs have a protein-sparing action which prevents the use of protein for energy
fat and glucose compound
without this compound, fat fragments combine with each other producing acidic ketone bodies
- accumulation of ketone bodies in blood (ketosis) can disturb normal acid-base balance
problems adults with chronic ketosis may face
- vitamin and mineral deficiencies
- loss of bone minerals - osteopenia and osteoporosis
- altered blood lipids
- increased kidney stone risk
- constipation, nausea and vomiting
- dangerously low glycogen stores
ketogenic diet
- used to reduce seizures in those with severe refractory epilepsy
- research is ongoing for other neurological conditions (brain tumors)
high blood glucose
insulin is secreted from pancreas
what does insulin stimulate
- uptake of glucose into cells
- storage of glucose into glycogen
- excess glucose in fat
low blood glucose
glucagon is secreted from pancreas
what does glucagon stimulate
breakdown of glycogen therefore glucose released into bloodstream
epinephrine
breaks down liver glycogen as part of the bodys defense mechanism in times of danger
how do you meet glucose needs?
- foods rich in free sugars and sugary drinks are not the best choices
- balanced meals, eaten on a regular schedule, help the body maintain its blood glucose level
glycemic index (GI)
measure of the ability of a food to elevate blood glucose and insulin levels
glycemic load
glycemic index multiplied by grams of carbs
when is glycemic load and index important?
individuals with diabetes to regulate their blood glucose
excess glucose
stored as glycogen until the muscle and liver are full to capacity
- 2/3 in muscle
- 1/3 in liver
- small emergency store in the brain
excess glucose after the liver and muscle
- the liver converts it into fats then stored in fat tissues
- fat cells may also convert glucose to fat
***fat cells can store unlimited quantities of fats
diabetes
impairs a persons ability to regulate blood glucose normally
type 1 diabetes
- little or no pancreatic secretion of insulin
- often diagnosed in childhood
- less common but is on the rise (10%)
- leading chronic disease among children and young adults
treatment of type 1 diabetes
- an external source of insulin
- meal planning to balance blood insulin and glucose concentrations
why is insulin given by injection or pump and not ingested orally?
insulin is an enzyme so we would digest it before it gets into the bloodstream
type 2 diabetes
- body produces insulin at first - then insulin resistance
- as blood glucose rises, so does blood insulin
- eventually pancreas becomes less able to make insulin
- often diagnosed in adulthood
- most prominent type of diabetes (90%)
if drugs are necessary for type 2 diabetes, what do they do?
- may stimulate insulin secretion
- may improve tissue uptake of glucose
- external source of insulin may also be used
type 2 diabetes and genetics
there is a genetic component to type 2 diabetes susceptibility
- higher risk with family history
indigenous communities and diabetes
- higher risk of diabetes
- lack of access to healthy, nutritious and affordable foods
type 2 diabetes and obesity
- people with diabetes require more insulin
- the more body fat, the more insulin resistant, the higher the blood glucose
- even people who are moderately overweight exhibit slightly elevated blood glucose (impaired glucose tolerance)
impaired glucose tolerance
blood glucose levels higher than normal but not high enough to be diagnosed as diabetes
- prediabetes
tighter glucose control
less severe complications
oxidation that accompanies elevated blood glucose
a diet high in antioxidant-containing veggies and fruits may be protective, but more research is needed to confirm the oxidation hypothesis
managing diabetes
- control lifestyle factors - weight
- nutrition (weight control)
- in those who are overweight, weight loss alone can help control diabetes
diet controlling diabetes
- adequate in nutrients
- adequate fibre
- moderate in added sugars
- provides a controlled amount of total carbs
- low in saturated fat and provides unsaturated oils
- adequate but not too high in protein
PA and type 2 diabetes
- helps achieve and maintain a healthy body weight
- heightens tissue sensitivity to insulin
- increasing PA, even without weight loss in those who are overweight seems to delay diabetes onset
- increased activity, even without weight loss, often helps to control diabetes
canadian diabetes association
- maintain regularity in timing and spacing of meals to optimize glycemic control
- substitute added sugars for other carbs
- provide control of BG, lipids and body weight
mediterranean diet
reduces major CV events and improve glycemic control
vegan or vegetarian diet
improve glycemic control, body weight, and blood lipids
- reduce myocardial infarction risk
DASH diet
improve glycemic control, BP and LDL-C and reduse major CV events
dietary patters emphasizing nuts, pulses (beans, lentils) and veggies and fruits
- improve glycemic control
- reduce CV mortality
hypoglycemia
low blood glucose
- very rare in healthy people
postprandial hypoglycemia
low blood glucose after a meal
- very rare - may occur after large weight loss
symptoms of postprandial hypoglycemia
- fatigue
- weakness
- dizziness
- irritability
- hunger
- rapid heartbeat
- sweating
- anxiety
- trembling
- headaches
fasting hypoglycemia
can be seen with cancer, pancreatic disease, diabetes, liver damage
symptoms of fasting hypoglycemia
- headache
- mental dullness
- fatigue
- confusion
- seizures
- unconsiousness
prevention of hypoglycemia
regularly timed, balanced, protein-containing meals
- avoid switching between low-carb dieting and sudden, large, refined carb doses and minimize alcohol beverages
what causes low blood sugar in people with diabetes?
- more PA than usual
- not eating on time
- eating less than you should have
- too much medication
- drinking alcohol
DRI committee recommendations (carbs)
AMDR: 45%-65% of kcals
- 225-325 grams of carbs/day (2000 kcals)
RDA: minimum 130 grams/day
WHO recommendations (carbs)
55%-75% of kcals
- 275-375 grams carbs/day (2000 kcals)
concentrated juice sweeteners vs. white sugars
- highly refined
- missing all of the beneficial nutrients and non-nutrients of original fruit
molasses vs. white sugar
- molasses can contribute iron if used frequently
- less sweet than other sweeteners so more is used
honey vs. white sugar
- honey is indistinguishable from sucrose
- sugar contains fewer kcal than honey per serving
free sugars
monosaccharides and disaccharides added to foods and beverages by the manufacturer, cook, or consumer
- sugars naturally present in honey, syrups, fruit juice concentrates
- DO NOT include the naturally occurring sources of sugars in intact of cute fruits, veggies and unsweetened milk
added sugars
all sugars added to foods and beverages during processing or preparation
- all added sugars are also free sugars
total sugars
account for all sugars present in foods and beverages regardless of the source
- includes added, free as well as naturally occurring sources of sugars found in intact or cut fruit, veggies and unsweetened milk
canadas food guide sugar recommendations
- prepare meals and snacks using ingredients that have little to no added sodium, sugars or saturated fats
- replace sugary drinks with water
replacing sugar
- energy-yielding sugar alcohols (nutritive sweeteners)
- no energy artificial sweeteners (nonnutritive sweeteners)
sugar alcohols
polysaccharides
1. do not contain ethanol or any other intoxicant
2. provide energy
3. produce a low glycemic response (body absorbs them slowly)
4. gas, abdominal discomfort and diarrhea from large quantities
5. do not contribute to dental caries
sugar substitutes - sugar alcohols
- erythritol
- isomalt
- lactitol
- maltitol
- mannitol
- sorbitol
- xylitol
artificial/alternative sweeteners
- make foods taste sweet
- do not promote tooth decay
- provide very little food energy, if any at all
- can be toxic is consumed in high doses
common artificial/alternative sweeteners
- saccharin
- cyclamate
- acesulfame-k (potassium)
- sucralose
- aspartame
- stevia
aspartame
- ~ 200x sweeter than sucrose
- used in a broad range of foods in canada
- made of phenylalaline and aspartic acid and a methyl group
- often mixed with lactose
aspartame in GI tract
fragments are split, absorbed and metabolized just as would any protein fragment
WHO recommendations for aspartame
ADI of 0-40 mg/kg body weight
when is aspartame consumption not safe?
people with PKU (phenylketonuria)
PKU (phenylketonuria)
- hereditary inability to dispose excess phenylalanine
- phenylalanine build-up can cause irreversible, progressive damage if left untreated in early life
metabolic by-products of aspartame
- methyl alcohol
- formaldehyde
- diketopiperazine
- these compounds are not toxic at the levels generated
stevia
- 300x sweeter than sucrose
- naturally sweet herb
stevia extract
natural sweetener that was not approves for use in foods sold in Canada until November 30, 2012
labelling of sweeteners
- amount of sweetener will no longer appear in list of ingredients
- all sweeteners will still appear in list of ingredients on product label
- they don’t have to be listed on front of package anymore
- aspartame must still be included in bold at end of list of ingredients
strategies for using artificial/alternative sweeteners
- moderation is key
- use does not automatically lower energy intake
- probably do not hinder weight-loss efforts
- safer for teeth
are sugar substitutes needed for healthy eating?
NO
suggestions from the government of canada
- choose water instead of drinks rich in sugar
- reduce added sugar in coffee and tea
- reading ingredient list and choose foods with little to no added sugars
- sweetening foods like yogurt or oatmeal with fruit
- add flavour, rather than sugar, with nutmeg, cinnamon or vanilla extract
