nutrition Flashcards
what are the immediate causes of major dental diseases?
diet, plaque and smoking
what are many diseases linked to?
oral inflammation
what can be assessed to look for diseases in the body?
the mouth
- corners
- tongue
- palate
- teeth
why do we see changes more easily in the mouth?
- oral epithelium has rapid turnover
- however healthy epithelium acts as a barrier to toxins
what is primary nutritional deficiency?
- inadequate selection of foods
- age, income, education
what is secondary nutritional deficiency?
Systemic disorder interfering with
Ingestion
Digestion
Absorption
Transport
Use of nutrients
which nutrients are required?
calcium, phosphorus, vitamins A,C and D, protein
which nutrients are bad?
CHO, sweet sticky foods etc.
what does nutrition mean?
describes the processes whereby cellular organelles, cells, tissues, organs and the body as a whole obtain and use necessary substances obtained from food (nutrients) to maintain structural and functional integrity
what are the 5 basic steps of dietary assessment?
- report
- identify food
- quantify
- frequency
- calculate intake
what are dietary allowances?
- quantitative amounts essential micronutrients, energy and protein to prevent deficiencies
- based on requirements
what are dietary goals?
- quantified national targets for selected macronutrients and certain micronutrients aimed at preventing long term disease
what are dietary guidelines?
- targeted at individuals- advisory statements for the whole population to promote overall nutritional well being and reduce diet related conditions
- broad targets, qualitative or quantitative
how many kcal should we eat on average?
women 2000kcal
men 2500 kcal
what is the SACN?
an advisory committee of independent experts that provide advice to government agencies and departments in public health
what is optimal nutrition?
the amount of a nutrient that:
- prevents deficiency symptoms
- optimises stores in the body
- optimises biochemical or physiological function
- optimises a risk factor for a disease
- minimises incidence of a disease
definition of requirement by panel
- need to replenish lost nutrients from diet/stores
what is the criteria or adequacy?
- needed to maintain a given circulating level, enzyme saturation or tissue concentration
- associated with the absence of any signs of a deficiency disease
- needed to maintain balance
- needed to cure a clinical deficiency
- associated with an appropriate biological marker of nutritional adequacy
DRV meaning
dietary reference values
EAR
estimated average requirement- of a nutrient which will meet the need of 1/2 the population
RNI
reference nutrient intake
- one above EAR which will meet needs of most people
- one below EAR which will meet needs of few people
safe intake
a level of nutrient at which there is no risk of deficiency but below a level where there is risk of undesirable effects
what are the categories in which DRV are adjusted for?
- Age and Gender
- Breast/formula fed infants
- Body Weight e.g. energy, protein
- Physical activity level (PAL) e.g. energy
- Pregnancy and lactation
- Elderly
who uses DRV?
- governments & NGOs in provision of food aid, food supplements and rationing
- food industry in development & marketing of new food products
- caterers in devising nutritionally adequate menus
- nutrition labelling - DRVs used to derive guideline daily amounts (GDAs) used on nutrition labels
- developing dietary guidelines & goals
- researchers & health professional in assessing the adequacy of diets of groups (or individuals but cautiously)
what are the 4 classes of nutrients?
macronutrients
micronutrients
water
alcohol
what is included within macronutrients?
carbs
proteins
fats and oils (lipids)
what is included within micronutrients?
minerals
vitamins
what is the chemical energy from nutrition used for?
electrical energy (maintain ionic gradients)
chemical energy (e.g. protein synthesis)
mechanical energy (e.g. muscle contraction)
heat energy (maintain body temperature)
what is energy measured in?
kilojoules (kj) - kilocals is the old system
what part of nutrition does energy come from?
macronutrients and alcohol
what is energy density?
energy a food contains per gram
is fat, carbohydrate or protein more energy dense?
fat
how is the total energy content of food calculated?
burn food and measure the heat released
how is the total energy content of food calculated?
burn food and measure the heat released
how is the total energy content of food calculated?
burn food and measure the heat released
how is the total energy content of food calculated?
burn food and measure the heat released
what is a low energy density food?
food with fewer calories per gram
what energy density do foods with high fat and low water content have?
high energy density
what are the three components which make up total energy expenditure?
- basal metabolic rate (60-75%)
- physical activity (10-40% but can reach 70%)
- thermogenesis (10-20%)
- additional requirement for growth
what is basal metabolic rate?
Vital body functions eg maintaining electrochemical gradient, cell and protein turnover, lung and heart function etc.
what is thermogenesis?
Including that though metabolising food (diet induced), throughmuscle action (dynamic and isometric) and through climate (coldinduced)
when is energy balance achieved?
energy intake= energy output
when is a positive energy balance desirable?
during growth, pregnancy and lactation
when is a negative energy balance desirable?
over medium term, fat stores will be used for energy and over long term, protein will also be used
(can lead to health problems)
what factors affect energy requirements?
- body size (bigger=more energy needed)
- age (more needed during growth)
- activity
- pregnancy/lactation
- disease/trauma/treatments (fever/stress increase metabolic rate, medications can increase/decrease rate)
what were used to set DRV?
Calorimetry
- Metabolic chamber: expensive and artificial
Indirect calorimetry
- O2/CO2 measurements: methodological limitations
Doubly labelled water
- Allows measurement without constraint
Energy intake data from surveys
what do DRV surveys assume?
Assumes the general population is in energy balance
Assumes intake data is accurate
why do we use estimated average requirement over reference nutrient intake?
health consequences due to over consumption
what makes up carbohydrates?
carbon, hydrogen and oxygen
how much of total energy intake do carbohydrates make up?
40-80%
what are the types of carbohydrates?
sugars and polysaccharides
what is a monosaccharide?
single sugar molecule
what is a disaccharide?
two sugar molecule
what are polyols?
sugar alcohols
what are examples of polysaccharides?
starch
glycogen
what is sucrose made of?
glucose and fructose (broken down by sucrase)
what is lactose made of?
glucose and galactose (broken down by lactase)
what is maltose made of?
glucose and glucose (broken down by maltase)
what is used in diabetic products?
sugar alcohols
what are the types of sugars?
extrinsic eg milk products
intrinsic eg fruit and veg
what is the difference between free sugars and added sugars?
includes all monosaccharides/disaccharides added to foods/beverages by the manufacturer/cook/consumer, plus sugars naturally present in honey/syrups/unsweetened fruit juices and fruit juice concentrates
- outside the cell (not fruit end veg etc)
what is the WHO guidelines for free sugar intake?
intake of free sugars should provide ≤10% of energy intake
what is starch?
storage carbohydrate
- insoluble in water
- cooking makes starch digestible
what are the two main types of starch?
amylose (unbranched)
amylopectin (highly branched)
what happens to food not digested in the small intestine?
It is fermented by the colonic microflora to short chain fatty acids and gases
Acetic, propionic and butyric acid
All have some health benefits and act as an energy source.
what is a prebiotic?
undigestible carbohydrate which stimulate gut healthy bacteria production
describe oligosaccharides as dietary fibre
- insulin and oligofructose
- not hydrolysed/absorbed in upper gastrointestinal tract
- reach the colon and are fermented by microflora of the colon leading to selective stimulation of the growth of the bifidobateria popultion
- named prebiotics
what are the three categories within dietary fibre?
Non-starch Polysaccharides
- Cellulose and non-cellulose polysaccharides (pectins, glucans, gums, arabinogalactans, mucilages, etc).
Resistant Oligosaccahraides
- FOS and GOS
Resistant Starch…
is fibre easily digested?
NO
which carbohydrates are not digestible?
cellulose
hemicellulose
oligosaccharides
modified starch
resistance starch
what is the best index of dietary fibre?
non-starch polysaccharide (NSP)
- also known as dietary fibre/roughage
what does NSP do?
- absorbs water in the GI tract
- faecal bulking
- increases transit time
- fuel for bacterial metabolism
- short chain fatty acids
- resistant to digestion/absorption
where is soluble NSP found?
oats
beans
fruit and veg
(lowers cholesterol)
where is insoluble NSP found?
wheat bran
(faecal bulking effect)
what are the roles of dietary fats?
energy
essential fatty acids
fat-soluble vitamins
what are the roles of lipids in the body?
store of energy
structural role in cell membranes
metabolic functions
what are fats mainly found as?
triacylglycerols
what are the structural factors affecting the properties of fatty acids?
- Number of C atoms (chain length)
- Presence of “double bonds”
- saturated and unsaturated fatty acids
- cis and trans isomers
- position of double bond, essential fatty acids
what % of dietary energy supply do proteins provide?
10-15%
how many different amino acids are there?
20
what are proteins made up of?
amino acids linked by peptide bonds (polypeptides)
what are proteins made up of?
amino acids linked by peptide bonds
what are essential amino acids?
cannot be synthesised in the body and/or cannot be synthesised in sufficient amounts to meet demand
what are non-essential amino acids?
can usually be synthesized from precursors in sufficient amounts to meet demand
what are acute and chronic illnesses associated with vit D deficiency?
preeclampsia
childhood dental caries periodontitis autoimmune disorders infectious diseases cardiovascular disease deadly cancers
type 2 diabetes and neurological disorders
why does vit D help prevent dental caries?
- needed for relevant mineral density
- absorbs, carries and deposits calcium in bones that support the teeth
what is the basic process of digestion?
hydrolysis
which enzyme first digests starch to maltose?
amylase
which enzymes digest polysaccharides into monosaccharides?
maltase
lactase
sucrase
isomaltase
where is amylase found?
saliva and pancreas
why do monosaccharides not require digestion?
they are absorbable forms of carbohydrates
what are examples of monosaccharides?
glucose and fructose (found in fruits)
what is a primary lactose intolerance?
loss of lactase at weaning
- therefore lactose is not hydrolysed, passes to the bowel metabolised to SCFA, gases
how is primary lactose intolerance diagnosed?
H2 in breath for lactose malabsorption
what is a secondary lactose intolerance?
from infection/illness which gives reduced lactase expression
what are examples of sugar transporters?
- GLUT family
- SGLT (sodium glucose transport family)
what are glucose transporters regulated by?
dietary CHO
what happens to insulin levels after eating?
increase
what happens to glucagon levels after eating?
decrease
what happens to blood glucose and triglycerides after eating?
increase
what happens to blood non-esterfied fatty acids and blood beta-hydroxybutyrate after eating?
decrease
what is the fate of dietary carbohydrate?
- glucose uptake by muscles
- liver and muscle glycogen synthesis
- oxidative disposal of glucose in muscle and other tissues
what is the common name for dietary triglycerols/ides?
fats (glycerol + 3 fatty acids)
what are lipids?
a group of water insoluble compounds of which triacylglycerols are the major form in diet
what are structural factors affecting the properties of fatty acids?
- no. C atoms
- presence of double bonds
what is a saturated fatty acids?
- all C atoms are fully saturated by H atoms
- associated with heart disease and cancer
what are unsaturated fatty acids?
oils
cis/trans isomers
what is the problem with fat digestion?
- fat is insoluble in water
- enzymes are in aqueous phase
what are examples of emulsifying agents?
- fatty acids
– monoglycerides
– cholesterol
– lecithin
– protein
– bile acids
what is a micelle?
A tiny particle made of substances that are soluble in water and that come together to form a ball-like shape
- polar head facing out
- non polar chain in
how are fatty acids absorbed?
- At brush border- lower pH at mucosa reduces solubility of lipid in micelles
- fatty acids absorbed by diffusion (but may be a carrier protein)
- NB medium chain fatty acids do not need micelles
how are proteins digested?
first digested into amino acids or di/tri peptides
which enzyme in the stomach digests 20% of proteins in the stomach?
pepsin
how are proteins digested in the small intestine?
- hydrolysed in lumen into peptides
- pancreatic proteases
- into amino acids
what are enterocytes?
absorptive cells in the intestine
how are amino acids absorbed?
- into enterocyte
- sodium-dependant co-transporters which bind amino acids after binding sodium
- conformational change
- sodium and aa released into cytoplasm
- contributes to generation of osmotic gradient which drives water absorption
what length of peptides are absorbed?
four or less amino acids
describe intact protein absorption
what are the main functions of macronutrients?
To provide energy in sufficient quantities
To provide range of building blocks
To provide essential nutrients we cannot make ourselves
when is the absorptive stage?
- during and right after a meal
lasts 4-6 hrs
what is the postprandial state?
state after a meal
what is the fate of glucose in the postprandial state?
contributes towards energy metabolism
where does energy come from in the postabsorptive stage?
- GI tract is empty
- energy comes from the breakdown of our body’s reserves
- increased glucose release from liver
- increased lipolysis of triglycerides in adipose tissue
how does increased lipolysis spare glucose?
- free fatty acids oxidised to cover muscle energy demands
how does increased lipolysis spare glucose?
- free fatty acids oxidised to cover muscle energy demands
what is the first available store of glucose?
the liver’s stores of glycogen (can maintain blood sugar levels for 4 hrs)
what are all of the events that occur in the absorptive state directed by?
insulin
what are the effects of insulin on CHO metabolism?
Stimulates glucose uptake by cells
Stimulates glycolyses
Stimulates glycogen synthesis
Inhibits glycogen catabolism
what are the effects of insulin on lipolysis in adipose tissue?
The process of fat mobilisation is catalysed by the enzyme hormone sensitive lipase (HSL)
Thus, control of this enzyme has a major effect on the plasma concentration of FFA.
HSL is inactive when insulin levels are high.
HSL is inactivated by dephosporylation in response to high concentration of insulin.
how does insulin stimulate the process of re-esterification?
by provision of glycerol-3 phosphate
what is insulin release stimulated by?
Increase in blood glucose
Increase in amino acids in plasma
Neural stimulation of pancreas
Gut hormones
what is insulin release decreased by?
- reduction in blood glucose
- sympathetic neural stimulation
what is glucagon released by?
A-cells of islets of Langerhans
what is the role of glucagon in the regulation of metabolism during the post absorptive state?
- increases glycogen breakdown in liver
- increases lipolysis
- increases gluconeogenesis in liver
- increases ketone body synthesis
what does cortisol do?
opposes the action of insulin
starvation
what are the consequences of negative energy balance?
- a decline in metabolism
– decreases in bone mass
– reductions in thyroid hormones
– reductions in testosterone levels
– an inability to concentrate
– a reduction in physical performance.
what are the consequences of positive energy balance?
- Plaques can build up in arteries
- The blood pressure increases
- Total and LDL-cholesterol and TAG increases
- Insulin resistance develops which leads to development of type 2 diabetes
- risk for certain cancers increases
what is TAG?
Trans Alanyl Glutamine
how does cortisol help regain glucose homeostasis?
- increase blood glucose through gluconeogenesis
- plays an important role in glycogenolysis (the breaking down of glycogen glucose) in liver and muscle tissue by facilitation of the activation of glycogen phosphorylase
- redistributes glucose to areas of the body that need it most (the heart, the brain) and away from digestive and reproductive organs
what is the role of epinephrine and norepinephrine in control of nutrient metabolism during stress?
Provides increase in glucose, required for energy (ATP) production by
-Inhibiting insulin secretion by pancreas
-Triggering glucagon secretion in the pancreas,
-Stimulating glycogenolysis in the liver and muscle,
-Stimulating glycolysis in muscle
what is the role of growth hormone in control of nutrient metabolism during stress?
- Promotes lipolysis and fatty acid oxidation
- Reduces liver uptake of glucose and helps to
maintain plasma glucose concentration - Promotes gluconeogenesis in the liver
what is the hormonal response to surgery?
- Increased catabolism
- Anterior pituitary ACTH Increases
- Growth hormone Increases
- Adrenal cortex Cortisol increases
- Aldosterone Increases
- Insulin often decreases
- Glucagon usually small increases
- Thyroid Thyroxine, tri‐iodothyronine Decrease
what are vitamins?
groups of chemically unrelated organic compounds
how many vitamins are essential for the regulation of body processes and normal metabolic function?
13 (A,B,C,D,E,K)
why are vitamins essential to humans?
because we generally cannot make them
which vitamins can we make?
vit D is synthesised in skin upon sun exposure
vit K and some B are synthesised by gut flora
what is an example of vitamins converted in the body ?
beta-carotene converted to vit A
tryptophan converted to niacin
what are examples of fat soluble vitamins?
A, D, E, K
which vitamins are water soluble?
C and Bs
how are fat soluble vitamins absorbed?
by lymph, transported attached to protein, stored in liver/fatty acid tissues
how are water soluble vitamins absorbed?
directly into the bloodstream
what are the factors influencing the utilisation of vitamins?
- Availability – niacini in cereals is bound
- Antivitamins – avidin binds to biotin in raw eggs, prevents its absorption but released on cooking
- Provitamins – carotenes converted to Vit A
- Biosynthesis in gut by bacterial flora – Vit K
- Intestinal disease - coeliac / intrinsic factor – B12
- Interactions of nutrients – requirement of Vit E increased when high PUFA intake
how many essential minerals are there?
15-16
what are the three main functions of essential minerals?
- Constituents of bones and teeth
e.g. calcium, phosphorus, magnesium - Formation soluble salts which help control composition of body fluids
e.g. sodium, potassium, chlorine - Essential components of many enzymes & other proteins, necessary for release & utilisation of energy
e.g. iron, zinc
which mineral is soluble in water?
sodium and potassium
which mineral deficiencies are widespread in human populations?
iron and iodine
what are the two groups of compounds vitamin A is found in?
preformed vitamin eg retinol
provitamin eg carotenoids
what are the functions of vitamin A?
Growth and normal development
Vision
Regulation of gene expression
Antioxidant
Immunity
Red blood cell production
Cell differentiation
Tooth development, oral epithelial development
where is preformed vitamin A found?
liver, fatty fish, eggs, whole milk, cheese, butter
where is provitamin A found?
dark green leafy veg, red and orange fruit/veg
what is the result of a vitamin A deficiency on teeth?
- impaired tooth formation
- decreased oral epithelial tissue
- periodontitis
- enamel hypoplasia
what are the toxic effects of excess vitamin A?
- acute- vomitting, headache
- chronic- bone and muscle pain, alopecia
- teratogenic- affects foetus in utero, spontaneous abortions
what are B vitamins essential for?
cell metabolic activities
what is a source of thiamin?
cereals, meats, legumes, yeasts
what is a source of riboflavin?
milk, cheese, eggs, leafy green veg
what is the function of biotin?
Important in lipogenesis, gluconeogenesis
Catabolism of branched chain amino acids
Widely available in foods deficiency is very rare
what is the best known function of vitamin C?
antioxidant, collagen synthesis
what disease can develop from a lack of vitamin C?
scurvy
what disease can develop from a lack of vitamin D?
rickets in children (bowed legs)
osteomalacia in adults (softening of bones)
which is the most toxic of all the vitamins?
Vitamin D (from oral intake)
what is the role of calcium in the body?
Bone and teeth structure, calcium phosphate
Contraction of muscles
Functioning of the nervous system
Blood clotting
Cofactor for enzymes and proteins
Functioning of several enzymes eg lipase
Glandular secretions
Cell signaling
at what age is peak bone mass reached?
30-35, when bones is strongest
what is the role of iron in the body?
Component of haemoglobin
- oxygen transport around the body
- normal blood formation
ATP production: e.g. cytochromes in electron transport
Plays an important role in enzyme reactions e.g. antioxidant enzyme calatase, cytochrome P450
Provides small oxygen reserve in muscle e.g. myoglobin
Defence against infection in breast-fed babies e.g. lactoferrin
what food is haem iron found in?
red meat
what are the functions of zinc in the body?
Needed for the antioxidant enzyme superoxide dismutase (SOD)
Structural role in proteins e.g. zinc finger motif in proteins
Zinc is also required for the expression of multiple genes
Immune Function
what is the function of sodium in the body?
maintains the volume of extracellular fluid (ECF)
helps maintain acid-base balance
is essential to muscle contraction and nerve transmission
allows the energy dependant uptake of nutrients (e.g. amino acids, glucose)
