Principles of nutrition Flashcards
Good nutrition
Good health
Prevention of disease
Recovery from illness
Nutrition
Sum of processes for living organisms to receive and use materials from environment to promote its own vital activities
Nutrients
‘Materials’
Substances digested, absorbed, promote body function
Carbohydrate, fat, protein, vitamins, minerals, water
Essential nutrient
Substance necessary for life, cannot be synthesised by body, must be in diet
Food
Substance eaten, digested and absorbed
Provides at least one nutrient - appropriate?
Diet
Foods selected
‘balanced’=adeqaute amounts of all nutrients
Malnutrition
Incorrect amount of one or more nutrients in diet (not just lack)
Undernutrition
lack of proper nutrition, caused by not having enough food or not eating enough food containing substances necessary for growth and health
Nutritional status
Intake of nutrients vs requirement –> state of health
Nutritional assessment
Measurement of nutritional status balance
Biochemical and anthropometric data, diet history
Dietician
Applies science of nutrition to individuals or groups
Health and disease
Metabolism
Changes constantly taking place in body due to tissue activity, transformation
Nutrients –> metabolism
–> energy liberated
–> tissue formed
–>body functions controlled and stimulated
Anabolism
Simple molecules –> complex, requires energy
Results in growth
Catabolism
Complex molecules –> simple, releases energy
Occurs during starvation and illness, energy intake decreases
Basic role of carbohydrate
Heat and energy
Basic role of fats
Heat and energy incorporated into body tissue
Basic role of protein
Tissue formation and repair broken down to produce energy
Basic role of vitamins and minerals
For regulation of body processes incorporated into tissue (minerals)
Basic role of water
Temperature regulation
Waste product excretion
Fluid medium essential for metabolism
Measurement of nutrients in food
E.g. energy
- calorie (kCal), unit of heat
- joule (kJ, mJ), unit of heat/ muscular/ electrical energy
- measured by oxidation of food
Nutrient requirements
COMA Report
SACN 2000
COMA Report
Committee on Medical Aspects of Food Policy Report (1991)
- dietary reference values for food energy and nutrients in the UK]
- estimated average requirement (EAR)
- reference nutrient intake (RNI)
SACN 2000
Scientific Advisory Committee on Nutrition
Advises PHE etc. on nutrition and related health issues
-reviews on vit A, iron, energy requirement, carbohydrates and health, vit D (2016), folic acid (2017)
Carbohydrates
Consist of C, H and O
Foods of plant origin e.g. grain, fruit, vegetables
CO2 + H2O –> sugar and starch
Monosaccharides, disacchardies, polysaccharides
Monosaccharides
Simplest form of carbohydrates
e.g. glucose, fructose, galactose
Disaccharides
Pairs of carbohydrate molecules
e.g. sucrose, lactose, maltose
Polysaccharides
Complex form of carbohydrates
e.g. starch (amylose - straight chain and amylopectin - branched)
Source of glucose
Made from starch
Found in fruit e.g. grapes
Source of fructose
Found in honey, fruits
Source of sucrose
Made from beet and cane
Found in fruit and vegetables
Source of lactose
Found in mammalian milk
Source of maltose
Found in sprouting grain
Source of starch
Storage carbohydrate in plants
Found in grains (++), potatoes, peas, beans, lentils
Source of galactose
Made from digestion of lactose
Not naturally occurring
Source of glycogen
Stored form of carbohydrate found in liver and muscles
Not found in meat, destroyed during hanging process
Non-starch polysaccharides
Dietary fibre: no enzymes so not digested , but for bulk, peristalsis , excretion; removed from refined carbohydrate food
Made from plant cell walls
Found in cereals, vegetables
Non-starch polysaccharides advantages
Bulky and take longer to eat
Prolonged feeling of fullness as stay in stomach longer
Prevent constipation, colonic cancer
-NSP and carcinogens: binds, dilutes by > faecal bulk, < transit time therefore < exposure
Non-starch polysaccharides disadvantages
Bind to minerals (Ca, Fe) –> deficiencies
Wind from metabolism of NSP in saecum and colon:
-methane, CO2, H2
-depending on type of NSP and bacterial flora
Insufficient energy intake: bulky and take longer to eat
Carbohydrate digestion
Broken down by enzymes (e.g. salivary amylase) to monosaccharides
Starch - longer digestive process
Disaccharides more readily absorbed (quicker energy source)
Carb release from liver
Metabolised for energy e.g. glucose only for brain, NS, RBCs
Converted into glycogen, stored in muscles and liver
Converted into fat when glycogen stores are full
Glycaemic index
GI 1-100
Ranks carbohydrates
Rate at which carbohydrate reaches bloodstream as glucose
Important to maintain blood sugar level 3.5-10mmol/l (hormonal control)
Low glycaemic index
Slow and steady release, levels constant and stable
< insulin resistance and weight control
Less carbohydrate leads to
More fat metabolism (ketoacidosis)
Depletion of body tissue (protein)
Carbohydrate in our diet
40-80% of energy intake
Foods cheap, plentiful, palatable, easy too prepare, low fat content
Starch(64%)>sucrose>lactose>fructose(3%)
High fibre, slow release - regulate blood sugar
Can also contain vitamins, minerals, some protein and fat
Guidelines: sugars
WHO March 2015
Free sugars
<10% strong recommendation (12 tsps/dy)
<5% conditional recommendation
Reduce throughout life course
Guidelines: sugars
SACN July 2015
Commissioned by DH and FSA
Recommended <5% free sugars
Average intake is ~11.5% (adults) therefore considerable challenge; great changes in dietary behaviour
-food labels display total sugar
Free sugar
Added sugar, plus naturally present in honey, syrup, unsweetened fruit juice
- replaces Non-Milk Extrinsic Sugar and ‘added’ terms
- does not include lactose in milk and milk products
“trends”
Sugar - current baddie
Fat/ carbohydrate debate (>obesity, >diabetes)
Is sugar the culprit?
Rising levels of heart disease (CVD) in 60s - Seven Countries Study
Current concern with impact on general and long term health, as well as (well known) dental impact
Seven Countries Study
Data not included of high fat, low heart disease and vice versa; plus not separate sugar
‘Fat makes you fat’; manufacturers low fat products (5% not low), with sugar substituted for taste
John Yudkin 1972
Sugar consumption
‘new’ vs fat
Current concern with impact on general and long term health, as well as (well known) dental impact
Fats
Consist of C, H and O (patterns and proportions) Fatty acids (sat, monounsat, polyunsat) + glycerol --> triglyceride
Saturated fat
Butter, cheese, full-fat milk, pizza, takeaways, pies
Monounsaturated fat
Olive, nuts, avocado
Polyunsaturated fat
Omega 3: oily fish, soya bean
Omega 6: sunflower seeds, wheat germ, corn
Trans fatty acids
Hydrogenated
In frying and baking fats
Essential fatty acids
For structure and function of cell membranes
To regulate cholesterol metabolism
Vegetable and marine oils
Sources of fat
Meat, dairy, eggs, vegetables (e.g. olive, coconut oils)
Cholesterol
LDL, HDL
From diet and synthesised in body
Associated with animal tissues
-full-fat dairy products, fatty meat, egg yolks, offal
Oils
Fats that are liquid below 20 degrees
Digestion of fats
Digestion in stomach and small intestine
Broken down to constituents, may reform as triglycerides
Functions of fats
Energy for tissue activity and body T maintenance
Incorporated into body structure e.g. brain and nervous tissue
Hold position and protection of vital organs
Insulation (subcutaneous heat loss)
Satiety - presence in duodenum delays stomach emptying
Provide fat-soluble vitamins and assist absorption
Fats body stores
Under skin and around abdominal organs (interchanged not inert, mobilised for fuel)
Dietary component of fat
~35% of energy intake from fats
70-95g/day
20-30g/day sat
Proteins
Main constituent of every living cells
Consist of chains of amino acids
CO2 + H2O + nitrogen-containing compounds (N and mineral elements e.g. iron) –> amino acids –> peptides, proteins
Peptides and proteins can convert to amino acids by transamination in liver
Proteins found in
Meat (myosin) Fish Eggs (albumin) Cheese Milk (caesin) Nuts Pulses e.g. lentils, beans Cereals e.g. wheat (gluten) RNI 45-55g/ day
Essential amino acids
Can’t be made
Functions of proteins
Replacement during metabolism and wear and tear
-e.g. hair, nails, skin, digestive secretions, bone, dentine, epithelium, antibodies
New tissue production e.g. growth, recovery from injury, pregnancy, lactation
Forming enzymes, hormones
Energy source
Digestion of proteins
Into amino acids and dipeptides and tripeptides
Fate of proteins
Structural proteins, converted into other aas, oxidised for energy
Vitalamine
Rice - beriberi in chickens (funk, 1911)
Vitamin C
Citrus fruit juice
Sailors’ scurvy (Lind, 1753)
Vitamins
Organic (or related) substances with specific biochemical functions
Essential for normal metabolism (promote reaction/s)
Sources of vitamins
In diet (e.g. Vit C only)
Some manufactured if enough precursor (pro-vitamin)
-beta carotene –> vit A
-vit D (diet) made in body, converted in skin by UV irradiation (for CA metabolism)
-vit K and some of B group vits made by intestinal bacteria (+ diet)
Water-soluble vitamins
Excreted, not stored
C and B group
Fat-soluble vitamins
Harmful as stored
A, D, E and K
Requirement of vitamins
Not known exactly (varies between people)
COMA: recommendation meet requirement of average healthy person
SACN: RNI for vitamins and minerals 2002-2017
Minerals
~3% of body weight
Essential constituents of soft tissues, fluids, skeleton, teeth
Incorporated into enzymes, proteins and soluble salts
Many sources
Examples of minerals
Calcium, sodium, potassium (bananas), iron (e.g. fruit and veg), zinc
-haemoglobin = iron-containing oxygen-transport metallo-protein
Water
~65-70% of body weight
Fluid medium for almost all body processes
Intra- and extra-cellular fluids
Body secretions, excretions
Sufficient urine flow, prevention of constipation
Joint lubrication
T control (lung and skin evaporation)
Death after a few days (compared to protein, fat, carb reserves)
Sources of water
Beverages (milk, tea) Fruit and veg (80-90%) Bread (~35%) Fish (65%) Meat (50-70%)
Metabolism to water
Protein, fat, carb –> water in hibernation
Water loss
Urine, faeces, sweat (lose salt), exhaling, vomiting, diarrhoea, haemorrhage, exudate from burns
Water balance
Thirst, kidney regulation
Water intake
- 5-3l/day
- climate and activity
- drinks (1L), food (1L), metabolism (0.5L)
Too much water
Kidneys can’t keep up excretion
Blood diluted, lower salt concs
Water moves from blood to cells & organs
Brain swells and prevents vital functions
Ecstasy
–> thirst and >ADH
Marathon runners
Over consumption and retention of water, plus sweat and salt loss
Energy
From oxidation of carbohydrates, fats, protein and alcohols in diet
Needed for
-growth and maintenance of body tissues
-maintenance of body T
-voluntary and involuntary muscle movement (heart, GIT, respiration)
1g carbo
16kJ
4kCal
Most efficient source
1g fat
37kJ
9kCal
1g protein
17kJ
4kCal
Takes time to turn into energy, needs energy
1g alcohol
29kJ
7kCal
Basal metabolism
Amount of energy required for basic processes e.g. heartbeat, respiration, cellular activity
Healthy balanced diet
Lots of fruit and veg (40%)
Starchy staple foods (wholemeal bread, wholegrain cereals, including B vits and fibre) 40%
Protein rich foods (lean meat, fish, eggs, lentils)
Some dairy foods (pref. lower fat variety)
Food Standards Agency Guidelines
Base meals on starchy foods
7 portions of different fruit and veg per day
2 portions of fish per week including 1 portion oily fish
Cut down sat fat and sugar
Eat less salt (<6g/day)
Get active and try to be a healthy weight
Drink plenty of water
Limit alcohol intake
Diet for treatment of disease
Diabetes, gluten sensitivity
Diet-related disease
Diet is the cause
>/< nutrient (e.g. scurvy, fat-soluble vitamins)
Dietary toxins (e.g. hydrocarbons from smoking processes)
Contaminated food (bacteria, pesticides, heavy metals)
Diet-associated disease
Diet is a contributory factor
< Infectious diseases - hygiene, antibiotics
> degenerative disease - CVD, malignancies, linked to diet
Dentist’s role
DBOH
- healthier eating advice
- good dietary practice guidelines
Diet and disease
WHO/FAO
“Diet, nutrition and the prevention of chronic diseases”
-obesity, type 2 diabetes, cancer, CVD, dental diseases, osteoporosis
-diet (and exercise) throughout life can reduce threat of global epidemic (remember ageing)
Other considerations
Pesticides and organic produce Additives, fortification Dried foods Processed foods (and lifestyle) GM foods Cooking effects, food storage Alcohol -carb content; energy source; damage to liver, brain Food supplements Food labelling (RDAs/GDAs) -complex
