Week 1 - DRV & Alcohol Flashcards
EAR
estimated average requirement
meet 50% of the whole population - assuming normal distribution
LRNI
Lower reference nutrient intake - 2 SD below from the normal, meet 2.5% of the whole populations needs
RNI
reference nutrient intake - 2 SD above the normal and meets 97.5% of the whole populations needs
Nutrient - macro/micro
Nutrient is something that gives essential nourishment to function
macro - carb, protein, fat, alcohol
micro - vitamins & minerals
nutrient requirement equation
nutrient requirement = metabolic demand / efficiency
* not everyone has the same
Safe intake
Intake considered fine for most people but not too high that could cause adverse effects
Used for nutrients/minerals where there is insufficient information
DRV - important notes
Dietary reference value
- apply to healthy people
- doesn’t apply to those with disease or metabolic abnormalities
- assumes all other nutrient requirements are met
- knows that not 100% of nutrient gets absorbed (exception made for Iron, this is accounted for)
Data to determine DRV’s
- Observational - look at populations with deficiency or excess
- Balance studies - intakes known and match losses
- Physiological estimates - to meet needs of growth tissue e.g. milk production in lactate breastfeeding
- Functional studies - intake associated with optimal functioning
- Clinical studies - e.g. how to cure vitamin D deficiency
Defining adequacy
- Have safe upper limits
- Prevent deficiency
- Optimise body stores
DRV - Protein
EAR - 0.6g per kg of body weight per day
RNI - 0.75g per kg of body weight per day
- more required for infants, children, pregnant and breast feeding women
DRV - Energy
Derived from fat, carb, protein and (alcohol)
EAR - assumes normal distribution, 50% of population will require less, and 50% will require more
- Assumes intake matches appetite, based on total energy expenditure (TEE)
Total energy expenditure (TEE)
= basal metabolic rate (BMR) x physical activity levels (PAL)
– females 19-50y EAR = 8.1 MJ /1940 kcal
[Based on 60kg & PAL = 1.4 (inactive)]
– males 19-50y EAR = 10.6 MJ /2550 kcal
[Based on 74kg & PAL = 1.4 (inactive)]
DRV - Fat/ Carbs/ Sugars
Not DRVs set - no known deficiencies or toxicities
There are some essential fatty acids
Assumes 5% energy comes from alcohol
Assumes 15% comes from protein
DRV limitations
Limited to certain groups .e.g Men Some groups we don't know much about e.g. Children Data errors e.g self-reported data Some nutrients there is little known Needs to be updated 10-15yrs Requirements are only a best guess Safety margins can vary across countries
Ethanol
- Structurally like carb
- metabolically like fatty acid
- High energy content
- ‘Empty calories’ because no nutrients except folate in beer
- Not essential because no essential nutrients
- In UK it’s assumed that 5% energy comes from alcohol
Alcohol upper limits
- Max 14 units / week
- If drinking max units, spread over 3 days
- Risk of cancers, increases the more regularly you drink
- 1 unit = 10ml/8g of alcohol
Alcohol - pregnant women
- Advice is: no alcohol
- Risk of fetal alcohol syndrome with mental and physical defects and long term issues
Typical alcohol units
Spirit 40%: 25 ml = 1 unit
White wine 11-14%:
125ml (1.5 units)
250 ml (3 units)
750ml bottle (9-10 units)
Red wine: 12-15% slightly more than above
Beer 4-8%
1 pint 569ml = 2.3-4.5 units
Absorption & metabolisation of alcohol
- Absorbed by GI tract - peak concentration in the bloodstream in 20-60 mins
- Transported by blood
- Metabolized in the liver by either
a) Alcohol dehydrogenase pathway
b) Cytochrome p450 system
AHD (alcohol dehydrogenase) pathway
Breaking down of alcohol
- ADH metabolises alcohol into acetaldehyde dehydrogenase (toxic)
- Acetaldehyde is further broken down into acetate
- Ends with carbon dioxide + H2O for easy elimination
- Oxidation: Generates NADH at the expense of NAD+, promotes fatty liver and lactic acidosis
- Acetaldehyde: impairs protein function and causes cirrhosis
Cytochrome p-450 system
Also known as MEOS (microsomal ethanol oxidising system)
- Occurs in chronic alcoholism
- Ethanol gets oxidised
Alcohol related liver diseases
- fatty liver disease
- cirrhosis
- metabolic tolerance
- lactic acidosis
Metabolic Tolerance
Heavy drinkers can become tolerant b/c of metabolic adaptions
- ADH also converts vitamin A into retinal (for vision).
Chronic alcohol consumption reduces retinal = worse vision
Other adverse effects of alchol
- mental health
- injury risk
- Liver, breast, colon, oral, pharyngeal, laryngeal, oesophagal cancer (some cancers have mixed research but upper GI tract cancer shows correlation)
- stroke risk
