Nutrition Flashcards
nutrient
a substance obtained from food that is used by the body.
essential nutrient
substance that MUST be obtained from food
body cannot synthesize it
or cannot synthesize in sufficient quantities
or supplements
supplements were not explicitly mentioned on notes, so pay attention to multiple choice options
what happens if essential nutrients not taken
adverse effects on health
adverse effects may disappear when essential nutrient is taken
” unless permanent damage already taken place
6 classes of essential nutrients
vitamins
minerals
carbohydrates
lipids
proteins
water
micronutrients
vitamins and minerals
required in small amounts by the body
present in small amounts in the body
not broken down for energy
role of micronutrients
structural role (some)
regulatory role (most)
macronutrients
carbohydrates, lipids, proteins
required in large amounts in body
present in large amounts in body
can be broken down in body
macronutrients – structural or regulatory roles?
can have structural/regulatory roles
nutrition research
uses scientific/academic research methodologies to obtain information about nutrition
important to replicate findings
important for peer review of findings
what to check for when evaluating nutritional information
evidence from various studies
peer reviewed info
studies replicated
where is reliable information about nutrition found?
peer reviewed journals
registered dieticians
volunteer organizations, non-profit societies
Health Canada
NIH (US)
government sources
beware of…
sales pitch
claims that sound too good to be true
(extreme claims)
Dietary reference intakes
based on scientific research on nutrient requirements
intended for use by people in health professions (NOT THE PUBLIC)
requirements for Dietary Reference Intakes depend on the following variables:
age
gender
genetics
pregnant? lactating?
environment
current diet
E.g. # calories
other requirement variables
are there current deficiencies?
establish/maximize tissue stores?
decrease chronic disease risk?
what happens during deficiency of a micronutrient? What are the steps?
Lack in diet leads to
–> decrease in tissue stores, which leads to
–> biochemical changes, which leads to
–> clinical/anatomical changes, which leads to
–> death
DRI (Dietary Reference Intake) is applicable to
applies to already healthy people
specific based on gender & age
intended to be met by food, not supplements
already adequate intake of other nutrients is expected
categories of dietary reference intakes
DRI for most nutrients
vs.
DRI for energy and macronutrients
subcategories of Dietary Reference Intakes (subcategories under DRI for nutrients)
Estimated Average Requirement (EAR)
Recommended Dietary Allowance (RDA)
Adequate Intake (AI)
Tolerable Upper Intake Level (UL)
subcategories of Dietary Reference Intake (under DRI for energy & macronutrients)
Estimated Energy Requirement (EER)
Acceptable Macronutrient Distribution Range (AMDR)
Estimated Average Requirement (EAR) – DRI for nutrients
meets the needs of 50% of healthy people
specific to age/gender
applies to groups of people
Recommended Dietary Allowance (RDA) – DRI for nutrients
meets the needs of most healthy people (98% of healthy people)
RDA is based on EAR, so only set for nutrients with EARs established
used for individuals
Adequate Intake (AI) – DRI for nutrients
estimate that will maintain health
set when there is not enough evidence to establish EAR/RDA
used for individuals
Tolerable Upper Intake Level (UL) – DRI for nutrients
highest level of regular intake of nutrient that is acceptable for most
highest level unlikely to cause adverse effects to health
applies to most healthy people (98%)
where do toxic levels of micronutrients usually come from?
supplements
why do many nutrients not have UL established?
not enough evidence to set definite UL
however, that doesn’t mean that toxic levels don’t exist for that nutrient
note that DRI for Energy is distinct from
DRI for macronutrients
see following slides
Estimated Energy Requirement (EER) – DRI for energy
estimated energy intake that will maintain energy intake/output in 50% of people
balance intake/output = no weight (fat) gain/loss
RDA not used alongside EER, because it may cause energy intake above EER
applicable to adults who are maintaining the desired body weight/composition
Acceptable Macronutrient Distribution Range (AMDR) – DRI for macronutrients
distribution/ratio b/w 3 macronutrients
E.g.
Carb 45-65% of caloric intake
Lipids 20-35% of “
Proteins 10-35% of “
1 Calorie =
1 kcal
macronutrient, 1gram to kcal
carbohydates 4kcal/g
proteins 4kcal/g
fats 9kcal/g
(alcohol 7kcal/g)
nutrient density
nutrient contribution of foods
energy/caloric density = energy supply of foods
but nutrient density also refers to energy contribution of foods
nutrient dense foods =
many nutrients/kcal relative to the amount consumed
also –>
many kcal relative to the amount consumed
—> could be called calorie-dense (?)
DIETARY GUIDLINES (vs. Dietary Reference Intake)
intended for use by general public
E.g.
Canada’s Food Guide
–> helps improve health, meet nutrition needs, reduce chronic disease risk
2019 Canada Food guide
less prescriptive approach
based on flexibility
gives tips for healthy eating habits
recommends variety of healthy food choices
shows proportions of food (e.g. plate)
no prescriptive amounts
4 components of food labels
1) ingredient list
2) nutrient content claim
3) health claims
4) Nutritional facts table
1) ingredient list
in descending order by weight
2) nutritient content claim
must be measured
meet specific criteria
E.g.
low in fat, high in fibre, excellent source of…
3) Health claims
statements relating a food or “ component to risk of disease
only certain “Health Claims” are accepted in Canada
4) Nutrition Facts table
lists total amount of energy as well as amount of 13 core nutrients:
oTotal fat
o Saturated fat
o Trans fat
o Cholesterol
o Sodium
o Carbohydrates
o Fibre
o Sugar
o Protein
o Vit. A
o Vit. C
o Calcium
o Iron
% Daily Value (%DV) – based on 2000kcal/day diet and average
DRI values
general tool for comparing foods as nutrient sources
digestion
process of breaking down food into small molecules that can be absorbed
mechanical/chemical digestion
Mechanical digestion – breakdown … teeth and peristalsis
Chemical digestion – breakdown … acid (HCl) and digestive enzymes
absorption
Absorption – process by which small molecules enter the cells of the gastrointestinal tract (GI)
Lumen of intestine –> intestinal epithelial cell –> blood or lymph
mouth
mechanical and chemical digestion
- Saliva secreted from salivary glands
o enzymes for carbohydrate digestion
o mucous for lubrication
esophagus
food to stomach with peristalsis
no digestion technically (?)
stomach
mechanical and chemical digestion
- gastric juice containing HCl and enzymes
(prot digestion) - pH ~2
- secrete mucous …
protect lining of stomach - Little/no absorption
- Food + Secretions = Chyme
- in stomach for 2-4hrs
chyme
- Food + Secretions = Chyme
how long in stomach
- in stomach for 2-4hrs
absorption in stomach?
- Little/no absorption
what secrete in stomach?
mucous – protect lining
HCl/enzymes – digest food
small intestine
mechanical/chemical
Primary site of absorption
Upper part (duodenum) receives BILE, PANCREATIC JUICES
Bile
§ Formed by liver and stored in gallbladder
§ Contains bile salts to emulsify fats (aids in lipid digestion/absorption)
§ Contains bicarbonate ions (HCl3-) to neutralize acidic chyme
pancreatic juice
§ contains bicarbonate ions
§ contains digestive enzymes (for starches, fats, & proteins)
small intestine continued
- cells lining intestine also secrete brush border enzymes – important for disaccharide and protein
digestion - muscle action continues mechanical digestion and mixes chyme with bile and pancreatic juice
- pH ~5-7
- stays here for 3-10hrs
how long in small intestine
3-10hrs
pH small intestine
pH 5-7
what happens to chyme
mix with BILE & PANCREATIC JUICES
WHY BILE?
neutralize acidic chyme (BICARBONATE IONS)
WHY BILE? (2)
bile salts emulsify fats
lipid digestion/absorp
WHERE BILE FORMED?
liver
WHERE BILE STORED?
gallbladder
Pancreatic juices also contain …
BICARBONATE IONS
pancreatic juices contain …
digestive enzymes
WHAT ARE BRUSH BORDER ENZYMES
enzymes from BRUSH BORDER
ENZYMES FOR DISACCHARIDE & PROTEIN DIGESTION
WHAT IS BRUSH BORDER?
microvilli covered surface of epithelial tissue
Large intestine (colon)
little digestion, some absorption
stays 24-72hrs
do not secrete enzymes
has bacteria – have enzymes that digest food
secrete mucous for lubrication
absorption – water and some minerals
(e.g. Na & K)
large intestine how long?
stays 24-72hrs
large intestine what absorb?
water and some minerals
(e.g. Na & K)
how is GI tract regulated?
secretion of enzymes and peristalsis
under nervous system and endocrine system control
water
Carries nutrients throughout body
Solvent for minerals, vitamins, amino acids, glucose, etc
Removes waste from tissues/blood
participates in many chemical reactions
Joint lubricant
Shock absorber (eyes, spinal cord, joints, amniotic sac)
E.g.
CSF
maintain body temperature
dehydration
Water loss > water intake
heavy exercise or high temps
Increased risk for infants & elderly
micronutrient
substance obtained from food that is used by the body
for normal function, growth, and maintenance of body tissues
why RDA / AI
prevent deficiency disease
maintain tissue stores
UL
difficult to reach through natural foods (unfortified foods) alone
reached by taking supplements and fortified foods
poorly understood for most nutrients
supplements
Non-prescription Natural Health Products (NHP):
o vitamin & mineral supplements (single and multi-nutrient)
o amino acids
o essential fatty acids
o probiotics
NPN (natural product number)
benefit supplement?
o correcting problems with low nutrient intakes
o providing nutrients to reduce risk of chronic disease
or increase athletic performance
risk supplement?
o increased risks of toxicity
o contamination of supplements with other ingredients
o supplements cannot substitute for healthy eating
or living a healthy lifestyle
o “natural” does not mean safe or effective
vitamins functions (co-enzyme)
- co-enzymes – helps enzymes to catalyze reactions in body
E.g. (B vitamins, Vit. C, Vit. K)
vitamins functions (antioxidants)
E.g.
(Vit. C, Vit. E)
neutralize free radicals
vitamins functions (hormone precursors)
(Vit. A & D)
fat-soluble vitamins
Vitamins A, D, E, & K
ADEK
stored in body generally
toxicity problem common with which fat-soluble vitamins
Vit A & D
how fat soluble vitamins absorbed?
- Absorbed with lipids in small intestines
Vit K & Colon?
o Some Vit. K is produced by bacteria in colon,
can get absorbed there
lipid absorption impaired? FAT SOLUBLE VITAMIN ABSOROPTION WILL BE IMPAIRED.
Decrease bile production (liver disease)
Pancreatic disease (decreased enzymes required for fat digestion)
I.e.
PANCREATIC JUICES & BILE – Note also Gallbladder storing bile
how are fat-soluble vitamins transported in blood?
in-soluble in blood, like all lipids
transported via LIPOPROTEINS / binding proteins
Vitamin D
bone health (calcitriol?)
calcium absorption
vitamin d may reduce risk of
CVD, cancer, multiple sclerosis, etc
vitamin d toxicity (UL)
100ug/day
vitamin d recommendation
RDA 15ug/day (600IU)
maximize bone health
no sun exposure implied
vitamin A
regulate epithelium growth
important for vision cells (rods & cones)
vitamin A deficiency
night blindness
alopecia
vitamin K
activate coagulation factors (2, 7, 9, 10)
vitamin K deficiency?
prolonged bleeding time
vitamin E
antioxidant
protect membrane lipids from free radicals (“PEROXIDATION”)
vitamin E deficiency
peripheral neuropathy
Ataxia
water soluble vitamins
vitamin C
B vitamins
B vitamins list
B1 - thiamin
B2 - riboflavin
B3 - niacin
B5 - pantothenic acid
B6 - pyridoxine
B7 - biotin
B9 - folate
B12 - cobalamin
TRN
PPB
FC
water soluble vitamins
more easily excreted
except Vit B12 stored in liver
less likely cause toxicity
water soluble vitamins and food processing
Susceptible to destruction by food processing (heat during cooking, exposure to sunlight, leached into
cooking water, etc…)
heat, sun, boiling (water)
water soluble vitamins where absorb?
small intestine
water soluble vitamin how transport in blood?
soluble in blood
free in blood
or bound to proteins (some have carrier proteins)
water soluble vitamins coenzyme functions
coenzymes for reactions
involved in the breakdown of carbs, fats, and proteins into energy
water soluble vitamins functions in blood cells
synthesis of blood cells (folate (B9), B12, B6
Deficiencies = anemia
water soluble vitamins other functions
Nerve conduction – some B vitamins
Antioxidant – Vit. C
vitamin C
fruit/vegetable
antioxidant
coenzyme – Collagen synthesis
vit c deficiency
scurvy – poor wound healing, hemorrhages
vit c toxicity
UL 2000mg/day
diarrhea
kidney stones
increased iron absorption
vit c recommendations
maximize tissue saturation, minimize urinary excretion:
RDA men – 90mg/day
RDA women – 75mg/day
above “ = excreted in urine
how many servings of fruits/veg per day = ____mg Vit C
5 servings = 220-280mg vit C
Vitamin B deficiency (cause & symptoms)
see following slides
B1 (thiamin) deficiency
causes…
- alcoholism
- over-consuming milled rice
leads to…
- cerebellar symptoms (ataxia,
nystagmus)
- cerebral symptoms
(confabulation, psychosis)
B2 (riboflavin) deficiency
many causes for deficiency
leads to…
- scaling of lip borders
- magenta coloured tongue
B3 (niacin) deficiency
many causes for deficiency
leads to…
- pellagra
(diarrhea, dementia, dermatitis, &
if untreated, death)
B6 (pyridoxine) deficiency
causes…
- alcoholism
- hepatitis
- anti-TB therapy
leads to…
- scaling of lip borders
- convulsions
B12 (cyanocobalmin) deficiency
causes…
- aging
- poor nutrition
- removal of terminal ileum
leads to…
- anemia
- peripheral neuropathy
Folic Acid (B9) deficiency
causes…
- alcoholism
- pregnancy
leads to…
- anemia
- in early pregnancy can cause
neural tube defects
Pantothenic acid (B5)
deficiency is rare
leads to…
…
trace vs major minerals
arbitrary distinction
based on quantity found in the body or how much we need to consume daily
minerals functions
Cofactors for chemical reactions (Zn, Mg, Fe, Cu, Mn)
Electrolytes – fluid & ion balance – maintain electrical gradients across cell membranes
(Na, Cl, K)
Structural Roles – bone and teeth – maintain protein structure (Ca, P,
Mg, Zn)
part of transport proteins (Fe in hemoglobin)
part of hormones (I in thyroid hormones)
Signal transduction in cells (Ca, P)
mineral absorption
Mostly small intestine
how substances in plants affect mineral absorption
Substances in plants can bind to minerals and reduce absorption
(fibre, phytate, oxalate)
how does body regulate mineral absorption
Mineral status – absorption may be regulated so that it is increased in those with low levels
how do minerals compete w/ each other
Other minerals – some interfere with each other’s absorption
§ High Ca reduces Fe & Mg absorption
§ High Zn reduces Cu absorption
note example of plants and mineral
o 1 cup of milk has 300mg Ca - 95mg are absorbed
o 1 cup of spinach has 290mg Ca - 15mg are absorbed
minerals and toxicity
toxic at levels not far above recommended levels
(low safety margin)
Copper (Cu)
collagen synthesis
Zinc (Zn)
cell signaling
adequate immune function
Iodine (I)
thyroid hormone synthesis
Iron (Fe)
for hemoglobin (O2 carrying protein of RBC)
sources:
muscle protein
health concern:
deficiency = anemia –> decrease O2 carrying ability
Calcium (Ca)
maintain adequate bone health
source:
dairy = major source
health concerns:
deficiency = bone weakness –> leg bowing
Phosphorus (P)
function:
fluid balance
bone formation
enzyme control
sources:
protein foods (meat, milk, cheese, eggs)
RDA:
700mg/day
health concerns:
high phosphorus intake:
muscle spasms/convulsions
Chloride (Cl)
function:
fluid balance
immune function
part of HCl (stomach)
sources:
o Fresh fruit, vegetables, and whole grains
o Processed foods low in potassium
RDA/AI:
AI = 2.3g Cl/day (2300mg)
Almost all consumed as NaCl
Health concerns:
o High chloride intake
* May lead to hypertension in salt sensitive patients
o Low chloride intake
* Rare, but can occur with eating disorders
Potassium (K)
function:
fluid/electrolyte balance
part of mm contraction
nerve AP transmission
maintains BP
Sources
o Fresh fruit, vegetables, and whole grains
o Processed foods low in potassium
RDA/AI:
o AI = 3.4g/day (3400mg)
potassium health concerns
o Hyperkalemia
* High blood potassium
* Can alter normal heart rhythm resulting in heart attack
* Can occur in patients with kidney disease
o Hypokalemia
* Low blood potassium
* Can result from kidney disease, diabetic acidosis, or from some diuretic
medications
sodium (Na)
major electrolyte
fluid balance
pH regulation
muscle contraction
nerve AP
sodium (Na) sources
o Small amounts naturally present in most foods
o Added as salt (NaCl) to foods (~10% of salt eaten)
o During food manufacturing (processed foods account for ~75% of salt eaten)
Na where absorbed
Absorption
o 95-99% of salt eaten gets absorbed in small intestine & colon (not regulated)
o Na levels are regulated in the blood by strict control of urinary Na excretion
Na AI/UL
AI = 1.5 g/day (3.8g of NaCl)
o More if you sweat a lot
o UL = 2.3 g Na/day
o To minimize adverse effects of Na in blood pressure
o Typical North American intake = 2.3-5g Na/day
Na deficiency
occurs with excessive fluid loss (vomiting, diarrhea, sweating = dehydration)
Symptoms
* Muscle cramps
* Dizziness & Nausea
* Leads to seizure, coma, death
cause changes in nervous system function, which can alter proper muscle function (e.g. cardiac muscle)
Na health concerns
o Hypertension
high salt intake, high BP
o disagreements on effects of high sodium diets
= Some people more sensitive
increase Na sensitivity in…
Increased sodium sensitivity also seen with
o Hypertension
o Diabetes
o Kidney disease
o Old age
high Na –> higher BP –> higher CVD
high BP –> CVD has strong evidence
high Na –> higher BP is debated
how to reduce Na intake
whole foods
reduce sauce intake
read labels for sodium
reduced processed/outdoor foods
use other spices (e.g. pepper)
monosaccharide
simple sugar
one sugar unit
E.g.
fructose (fruits/honey)
glucose
galactose
fructose
most sweet
fruits, honey
sweetener (high fructose corn syrup)
glucose
second most sweet
used most in body
present in small amounts in fruits/vegetables
galactose
least sweet
in milk products
see lactose
disaccharides
two sugar units
2 monosaccharides linked
maltose
sucrose
lactose
maltose
glucose + glucose
note starch digestion
not generally found in foods (but part of breakdown)
sucrose
glucose + fructose
table sugar
in fruits, some vegetables, & grains
lactose
glucose + galactose
milk sugar
disaccharide to monosaccharide enzymes
maltose uses maltase
sucrose uses sucrase
lactose uses lactase
disaccharides must be
must be converted to monosaccharides before the body can use them
only one enzyme for each disaccharide
enzymes via Intestinal brush border
lactose intolerance
people lack digestive enzyme lactase
lactase normally decrease as a person ages
infants have high levels
during lactose intolerance——->
whole disaccharide remains intact in the intestines —> = GI discomfort
polysaccharide
many sugar units
w/ proper enzymes –> broken down into simple sugars
starch (polysaccharide)
glucose chains
plants
grains, legumes, tubers (potato)
fibre (polysaccharide)
chains of sugars
plant stems/leaves
does not get broken down to simple sugars
helps bowel movement health / GI health
cows have enzymes to break down fibre to monosaccharides
glycogen (polysaccharide)
chains of glucose
produced in body to store glucose
store glycogen in skeletal muscles & liver
not really via food
carbohydrate digestion (polysaccharide)
polysaccharide
up to 4 hours get to blood
in mouth
salivary amylase in mouth
– breaks long polysaccharide chains into DEXTRIN chains
– DEXTRIN also a polysaccharide
in small intestine
DEXTRIN broken to disaccharide
via PANCREATIC JUICES (ENZYMES)
THEN…
Brush Border Enzymes break down disaccharides
– BB enzymes = maltase, lactase, sucrase
Monosaccharides taken to liver & other cells
monosaccharides digestion
sugar can be in blood in 20 mins after eating
taken to liver & other cells via blood after reaching small intestine
Glucose metabolism
liver converts monosaccharides to GLUCOSE
where glucose go?
energy for cells
most tissue prefers glucose – But fats also used
Brain & RBC can ONLY USE GLUCOSE (not fat)
what happens if not enough carbs?
GLUCONEOGENESIS
make glucose from proteins/fats etc.
or KETONE BODIES as alternate energy for brain
—> Can cause problems (?)
how else is glucose used?
for other important molecules
RIBOSE for RNA/DNA synthesis
Note also glucose & Kreb’s cycle intermediates (???)
blood glucose regulation
eating = increase blood Glucose = increase INSULIN from pancreas = DECREASE BLOOD SUGAR
(glucose uptake by cells via Insulin)
blood glucose regulation when not eating
decrease blood sugar
–> increase GLUCAGON from pancrease
–> increase blood sugar
(GLUCOSE RELEASE FROM GLYCOGEN INTO BLOODSTREAM)
I.e.
glucose via glycogen
+
glucose via gluconeogenesis
tight regulation of blood glucose
fasting blood glucose
= 4-6mM (millimole) (per Litre?)
less than 3mM (per litre?) = Life-threatening (?)
greater than 6mM (per litre?) = dehydration / tissue damage
health conditions & glucose
type 1 diabetes
type 2 diabetes
complications of type 1/2 diabetes
dental caries (cavities)
type 1 diabetes
Insulin Dependent Diabetes Mellitus (IDDM)
10% of diabetics
Autoimmune disease
immune system attacks pancreas cells that produce insulin
–> I.e. lack of insulin
Usually before 20y/o
FATAL IF INSULIN NOT TAKEN
type 2 diabetes
Non-Insulin Dependent Diabetes Mellitus (NIDDM)
90% diabetics
usually after 40 y/o
becoming more common in younger people & children
type 2 diabetes cause
family history
lack of exercise & physical activity
obesity
diet
environmental factors (?)
type 2 diabetes mechanism
a) insulin released in decreased quantities
and/or
b) insulin released, but tissue becomes resistant to insulin
I.e.
less uptake of glucose
recommendation to decrease risk of type 2 diabetes
healthy diet
healthy body weight (body fat)
regular physical activity
complications of type 1/2 diabetes
via hyperglycemia
– dehydration (excess glucose released in urine
– excess urine production
– GLYCOSYLATION of proteins
(glucose attaches to proteins in blood)
I.e.
reduced circulation in some areas (Esp. EXTREMITIES)
ALSO
–> damage of endothelial cells of BV
–> INCREASED RISK OF ATHEROSCLEROSIS
kidney & eye disease
note GLYCOSYLATION of proteins in blood
= decreased circulation in some areas (ESP. extremities)
= damage to endothelial cells of BV
= increased risk of atherosclerosis
Note that sugar in blood can potentially be worse than saturated bad for atherosclerosis
note diabetes & eye disease
= damage to blood vessels around eyes
dental caries & carbohydrates/sugars
Bacteria digest carbohydrates around teeth
–> acids are biproduct of bacteria metabolism
–> erosion of enamel
–> cavities
dietary carbs recommendations
Carb requirement ~ 50-100g/day to prevent build up of ketone bodies (~10-20% of kcal)
RDA = 130g/d
o based on average amount of glucose used by brain (~25% kcal for a 2000kcal/d diet)
AMDR = 45-65% of total kcal as carbohydrates
o <45% makes it difficult to get enough nutrients that come from carb rich foods (fibre, vit. C, folate, etc…)
o >65% makes it difficult to eat enough protein & EFAs
carbohydrate recommendation for people who are physically active
“Recommendations for Athletes”
* 55-65% of kcal as carbs
- carbs are usually major fuel for muscle (from stored glycogen & blood glucose)
- glycogen stores are maximized by a high carb diet
fibre types
soluble
insoluble
soluble fibre
in water they swell up
form gel
where soluble fibre?
in fruits & legumes, oats & barley
“gums, mucillages, pectins, & some hemicelluloses”
effect of soluble fibre
slow gastric emptying & time through stomach and small intestine
§ feel full for longer
§ slows glucose absorption
soluble fibre & blood cholesterol
o decrease blood cholesterol by decreasing reabsorption of bile acids, and therefor increasing
bile acid synthesis from cholesterol in liver
does soluble fibre have laxative effect
no
insoluble fibre
in all plants
“esp high in bran, legumes, root vegetables & whole grain foods”
“cellulose, some hemicelluloses, & lignan”
insoluble fibre effect
o increases fecal bulk by not breaking down – attracting water
§ increases speed of movement through colon
o can have a laxative effect
§ decreases constipation & associated disorders
health benefits of fibre
the benefits of fibre alongside other components of a high fibre diet
o diets low in cholesterol & total and saturated fats
o high in phytochemicals & antioxidant vitamins
dietary fibre recommendations
= ~25g/d for women (Cnd avg 15-17g/d)
= ~38g/d for men (Cnd avg 19-22g/d)
too much fibre
- too much fibre is not good (~60g/d or more)
o GI discomfort
o Can bind to minerals and decrease their absorption
o Can displace nutrient/energy dense foods
3 groups of lipids
triglycerides
phospholipids
sterols
trigglycerides
major fat in diets
glycerol backbone (3 carbon alcohol)
+ 3 fatty acids (long chains of Carbon surrounded by Hydrogen)
function of triglycerides
energy storage
insulation
cushioning organs
phospholipids
glycerol backbone
+ 2 fatty acids
+ phosphate group (head)
amphipathic
–> head hydrophilic
–> tails hydrophobic
function of phospolipids
part of cell membranes
component of bile
assist with lipid transport
precursor of EICOSANOIDS (hormone-like substances)
sterols
E.g. cholesterol
& other compounds made from cholesterol (animals)
& plant sterols
function of sterols
part of cell membrane (structure when heat, fluidity when cold)
precursor to bile acids & STEROID hormones
fatty acids
chains of carbon atoms
bound to other compounds
not found free in foods, or body
Triglycerides and phospholipids contain fatty acids
types of fatty acids
saturated & unsaturated fatty acids
cis vs trans fatty acids
saturated fatty acids
no double bonds
i.e.
fully saturated with hydrogen
(single covalent bonds (?))
saturated fats @ room temp
tend to be solid
e.g. bacon fat
saturated fats where?
foods from animals
(dairy, meat)
saturated fats & oxidation?
not susceptible to oxidation
saturated fats & blood cholesterolal
increase blood cholesterol
increase risk of CVD
unsaturated fatty acids
one or more double bonds
include Monounsaturated fatty acids (one double bond)
& polyunsaturated fatty acids (more than 1 double bond)
unsaturated fatty acids facts
liquid at room temp
foods from plants
do not raise blood cholesterol (?)
MUFA & PUFA (unsaturated fats)
see following slides
PUFA (polyunsaturated fatty acids) –> rancidity
susceptible to OXIDATION
(chemical damage to molecules)
(causes rancidity in foods)
damage to cell membrane, DNA, & other molecules
damage increases risk of cancer & CVD
cis vs trans fatty acids
Hydrogen atoms around double bonds on SAME side
most Unsaturated fatty acids are CIS
trans fatty acids
produced by microorganisms
small amount found in dairy
made also by hydrogenation of plant oils
changes shape of fatty acid (HYDROGEN around double bond on OPPOSITE SIDE)
trans fatty acid behaves like…
saturated fats
solid @ room temp
increase blood cholesterol
some notes about naming fatty acids
location of first double bond (E.g. omega 3 / 6)
also via length of carbon chain
also via total number of double bonds
E.g.
alpha linolenic acid (type of OMEGA 3 fa)
–> first double bond @ carbon 3 (b/w 3 & 4) (“counting from omega end”)
other name: C18:3
I.e.
18 carbons in whole chain
3 double bonds in total
essential fatty acids
2
omega 3 & 6 (different types for each)
cannot be made in body
must obtain from food
why essential?
for cell membrane
for growth/development
precursor for other PUFAs –> to eicosanoids
–> i.e. regulation of clotting & inflammation
omega 6 fatty acids types
linoleic acid
arachidonic acid
linoleic acid
animal and plant fats
vegetable oils
growth & skin cell function
deficiency = growth problem, skin problem
LINOLEIC ACID IS PRECURSOR OF ARACHIDONIC ACID (other omega6 fa)
–> Used to make eicosanoids
–> inflammation response & blood clotting
(immune response)
types of omega 3 fatty acids
alpha linolenic acid
eicosapentaenoic acid (EPA)
docosahexaenoic acid (DHA)
alpha linolenic acid
high in canola oil, soy, flaxseed oil
small amount in animal fats
precursor for other omega 3 fa (eicosapentaenoic acid)
(docosahexaenoic acid)
EPA & DHA
o eicosapentaenoic acid [EPA]
§ precursor for eicosanoids that decrease inflammation and blood clotting
o docosahexanoic acid [DHA])
§ important component of cell membranes – found in high levels in the brain
are EPA & DHA made in plants?
EPA & DHA are not made in plants
o small amounts found in fatty fish oil, some shellfish, very small amounts in meat and
eggs
o deficiency is not well understood
§ Impaired visual and neural function
digestion of lipids
Lipids in our diet:
- 95% triglycerides
- some phospholipids and sterols (sterols are mostly cholesterol)
- fat soluble vitamins get absorbed with other lipids
where most digestion
small intestine
what essential for lipid dig
Bile is essential for lipids to be digested in this water environment
what bile do
o Bile helps pancreatic enzymes to be able to reach the fat molecules to cleave the fatty acids off
triglycerides, phospholipids and cholesterol
bile mechanism
§ Fats form droplets in intestine that make it hard for enzymes to penetrate to molecules inside
§ Bile contains bile acids and phospholipids that can interact with water and lipid
§ Fat droplets are broken into smaller droplets (emulsification)
§ Allows enzymes to access more lipid molecules
§ = digestion
efficiency
what bile also do
o Bile also interacts with the products (forms micelles) of digestion to bring them close enough to the intestinal cells to be absorbed into the cells
§ = digestion efficiency
triglycerides and phospholipids in intestinal cells
Once inside the intestinal cell
o Triglycerides and phospholipids reform
chylomicrons
o Reformed fat molecules combine with
a) proteins, b) cholesterol, and c) fat soluble vitamins
–> to form particles called chylomicrons
how chylomicrons go to blood?
o Chylomicrons enter lymphatic vessels & lymph transports chylomicrons to the blood
Bile acid recycling
o Bile acids do not get absorbed with products of lipid digestion (chylomicrons?)
bile?
o Absorbed later in the small intestine and returned to liver via blood (hepatic portal vein)
o Usually 90% recirculated back to liver (pretty efficient)
how fibre reduce cholesterol
o soluble fibre in small intestine
= binding of bile acids to soluble fibre
= excretion of bile acids in feces
= liver production of new bile acids from cholesterol
= lower blood cholesterol levels
how transport lipids?
lipids are not soluble in water/blood,
so transporting them in blood requires bind to other molec
(lipoproteins)
lipoproteins
- Chylomicrons
- VLDL (very low density …
- LDL (low density …
- HDL (high density …
Chylomicrons
Chylomicrons
o transports triglycerides and other lipids from intestines
o to adipose tissue for storage
o to the liver
where chylomicrons go?
o to adipose tissue for storage
o to the liver
VLDL
VLDL (very low density lipoprotein)
o transports triglycerides from the liver to other tissues
where vldl go?
from the liver to other tissues
ldl
LDL (low density lipoprotein)
o transports cholesterol from liver to other tissues
o known as “bad” cholesterol – can get trapped in arterial walls if inflammation is present
where what ldl go take?
o transports cholesterol
from liver to other tissues
HDL
HDL (high density lipoprotein)
o transports cholesterol from tissues to liver
o known as “good” cholesterol – can transport cholesterol from walls of arteries back to liver
hdl where what?
o transports cholesterol
from tissues to liver
why hdl good?
can transport cholesterol from walls of arteries back to liver
Lipids and Cardiovascular Disease (CVD)
Atherosclerosis
Blood LDL levels
w-3 Fatty Acids & CVD
Atherosclerosis
CVD – lipid deposits on arterial walls
atherosclerosis increased risk =
§ high blood cholesterol (as LDL)
§ high blood triglycerides (mainly as VLDL)
atherosclerosis protective measure?
o protective blood marker
§ high HDL levels
blood LDL levels & CVD
see following slides
why blood LDL increase?
o increase due to increased dietary cholesterol, saturated & trans fats
how decrease blood LDL? Decrease dietary cholesterol?
- but usually only results in small LDL decrease because liver often increases
cholesterol synthesis in response to decreased dietary cholesterol - although some people respond with greater LDL decrease
decrease blood LDL – decrease saturated fat?
- usually more effective than decreasing cholesterol
decrease blood LDL – decrease trans fat?
- effect similar to decreased saturated fat
- but, this will also support healthy HDL levels as high trans fats also decrease HDL levels
decrease LDL – increase dietary fibre?
- reduces LDL by reducing body’s cholesterol levels
why?
b/c decrease recirculation of bile acids
I.e.
cholesterol used to make bile
w-3 Fatty Acids & CVD
- reduce risk of death due to heart disease largely by reducing tendency of blood to clot
dietary lipid recommendations (AMDR)
Total Fats
AMDR = 20-35% of total kcal as lipids
o < 20% make it difficult to obtain sufficient EFAs
o > 35% make it hard to stay below upper limit for saturated fat & cholesterol intake
AMDR of lipids for “athletes”
AMDR for “athletes”
= 20-25% of total kcal as lipids
o To allow for high carb intake without reducing proteins
saturated fat AMDR
Saturated Fat
AMDR = < 10% of total kcal
trans fat AMDR
Trans Fat
AMDR = < 1% of total kcal
Essential Fatty Acids AMDR
Linoleic Acid (w-6) AMDR
= 5-10% of total kcal
a-Linolenic Acid (w-3) AMDR
= 0.6-1.2% of total kcal
why need protein?
o maintaining our amino acid pool to make peptide hormones, neurotransmitters, etc…
o producing strength & structure to tissue – connective tissue, epithelial tissue, tendons, ligaments,
bones, cartilage
o contractile proteins – muscle
o making proteins that carry nutrients and hormones through the blood
o producing all our body’s enzymes
o making membrane proteins
o hormones
o energy production
o maintaining the immunoglobulin pool (immune system)
o buffering various body fluids
o producing & maintaining DNA & RNA
what are proteins?
- chains of amino acids held together with peptide bonds
o amino group of one amino acid joins the carboxyl group of the next amino acid
how peptide bonds broken down?
o peptide bonds are broken by hydrolysis
§ this breaks proteins into amino acids and short chains of amino acids
how similar to lipid & carbohydrate?
- contain C, H, & O (like carbs and lipids), but also contain N
- the “R” group (side chain/amino group) is different for each amino acid
shape/form of protein vs function?
- the shape of the protein is key for its function
o although they can be chemically reproduced, it is difficult to reproduce the intricate shapes
types of proteins
- dipeptide – chain of 2 amino acids
- tripeptide – chain of 3 amino acids
- oligopeptide – chain of 3-10 amino acids
- polypeptide – chain of many amino acids
- protein – chain of > 50 to many 100s of amino acids
essential amino acids
20 (or 22) amino acids
body can produce 11 (non-essential via TRANSAMINATION (transferring amino groups)
CANNOT PRODUCE NINE (9)
9 = essential
some are conditionally essential (E.g. during infancy)
(during pathology?)
vegetable/plant proteins?
not contain all 9
eat variety of plant proteins to get 9
or eat meat/animal protein
protein digestion
in stomach:
o HCl acid denatures proteins to expose whole molecule to enzymes
o PEPSIN (enzyme secreted in stomach)
breaks protein into shorter polypeptides
proteins in small intestine
proteases & peptidases FROM PANCREAS
–> break proteins and large polypeptides into small
polypeptides, tripeptides, dipeptides, and amino acids
in small intestine after pancreatic enzymes/juices
o enzymes on brush border break small polypeptides to
tripeptides, dipeptides, and amino acids
what can be absorbed into intestinal lining?
o only tripeptides, dipeptides, and single amino acids can be absorbed into intestinal cells
what happens @ intestinal cells?
o Tri & dipeptides broken into amino acids before entering blood
what happens to amino acids?
uptake by tissues E.g. liver
put together to make proteins
or gluconeogenesis (glucose)
or broken down for energy directly (?)
or made via fats (AAs?)
what happens when AA gets used for energy/energy/fats?
results in a toxic ammonia molecule
(NH3)
o liver converts ammonia to urea
o kidney excretes urea from body
Protein Synthesis
amino acids needed
non-essential via body or food
essential via food
how is structure of protein determined?
via DNA of a gene
how protein made?
o transcription – genetic information in DNA is used to make a messenger RNA (mRNA)
copy
o translation – converting genetic information on mRNA into a chain of amino acids to form a
protein
dietary protein – quality of protein
- Complete Protein (aka: high quality protein)
o dietary protein containing all of the essential amino acids in relatively the same amount the
human beings require
o animal protein, soy, quinoa
- Incomplete Protein (aka: lower quality protein)
o low in one or more essential amino acids
o most plant proteins, especially grains
§ plant proteins tend to be highly associated with fibre, which also decreases their
“digestibility”
note fibre & protein digestion
§ plant proteins tend to be highly associated with fibre, which also decreases their
“digestibility”
- Complementary Proteins
o two different proteins whose amino acid profiles complement each other, so that the
essential amino acids missing from one, are supplied by the other
o ie: eating rice and beans together
quantity of protein
o animal proteins generally more nutrient dense than plants
o higher nutrient density for proteins = meat, seafood, dairy, legumes
nitrogen balance
nitrogen balance is when:
o nitrogen incorporated into the body each day = nitrogen excreted each day
o negative nitrogen balance = excreted > added
o positive nitrogen balance = excreted < added
negative nitrogen balance
o protein malnutrition
o dietary deficiency of even 1 essential aa
o starvation
o uncontrolled diabetes
o infection
positive nitrogen balance
o growth
o pregnancy
o recovery from a condition associated with negative nitrogen balance
protein RDA
RDA = 0.8g protein/day/kg body weight
o should be high quality mixed protein diet for both vegetarians and omnivores
AMDR = 10-35% of kcal
o < 10% = risk of not meeting protein requirement
o > 35% = risk of inadequate carb & fat intake
inappropriate protein nutrition –> effects on health (low protein intake)
o most widespread form of malnutrition worldwide
o Marasmus
o Kwashiorkor
o also a risk in North America
low protein intake affects who?
o most widespread form of malnutrition worldwide
o affects mostly children
o many die due to impaired immune system function
o Marasmus
o severely inadequate intakes of protein, energy, and other nutrients
§ severe wasting of muscle tissue
§ stunted physical growth
§ stunted brain development
§ anemia
§ fluid & electrolyte imbalances
o Kwashiorkor
o Extremely low protein intake in early weaning, complicated by infections
§ some weight loss and muscle wasting
§ edema resulting in abdominal distention
§ delayed growth & development
§ skin sores & brittle hair
who in north america?
o alcohol/drug users
o homeless
o low income elderly
o those with illnesses that interfere with eating
§ anorexia nervosa
§ AIDS
§ cancer
§ tuberculosis
