dietary reference values Flashcards
how can we tell if people manage sufficient amounts of nutrients to maintain adequate health
by comparing their intakes with recommendations
who were DRVs published by in 1991
DoH
whys it important to set standards for nutrient intake
To prevent deficiency symptoms.
To optimise body stores of a nutrient. E.g. to optimise vit D stores
To optimise a biochemical or physiological function. E.g. need sufficient amount of nutrient if its maybe a cofactor for an enzyme to work
To minimise risk factor for some chronic disease. E.g. reducing sat fatty acid intake reduces levels of cholesterol so reduce CHD
To minimise incidence of a disease. E.g. increase fibre intake reduce risk of colorectal cancer
what was the name of the USAs first version od dietary standards produced in 1943 by the national research council
the Recommended Dietary Allowances (RDAs).
what did the RDAs in 1943 aim to provide
a yardstick against which diets or food supplies could be assessed to determine their adequacy.
how many nutrients did the RDAs provide info on in 1943
10 nutrients
Modern day equivalents provide info on about 30 or more nutrients.
when were the UK Recommended Daily Intakes (RDIs) and the UK Recommended Daily Amounts (RDAs) introduced
1969 UK Recommended Daily Intakes (RDIs)
1979 UK Recommended Daily Amounts (RDAs)
what happened to the name of the RDAs in 1991
Nomenclature changed – ‘recommended’ led many to believe it represented min desirable intake for health.
so name changed to UK Dietary Reference Values (DRVs) published.
what did the DRVs apply to
Apply to the range of intakes based on an assessment of the distribution of requirements for each nutrient.
who did the DRVs apply to
heathy people
Not appropriate for those with disease or metabolic abnormalities.
DRVs for 1 nutrient presuppose what
that requirements for energy & all other nutrients are met.
e.g. prot & vit A – If vit A req met but not prot, insufficient RBP to transport vit A. – nutrients work together
why do you need to use caution when assessing diets of individuals with the DRVs
so making sure that you don’t use any strong statements
what are uses of DRVs
Assessing diets of individuals - Use caution!
Assessing diets of groups of people and populations.
For providing guidance on composition of meals and diets.
Food labelling e,g, reference intake on food packaging are based on DRVs
name the 3 levels that the UK 1991 COMA (Committee on Medical Aspects of Food Policy) panel set for DRVs
Estimated Average Requirement (EAR)
Lower Reference Nutrient Intake (LRNI)
Reference Nutrient Intake (RNI)
what is the EAR
Estimated Average Requirement (EAR)
Average requirement that Will meet the needs of 50% of the whole population.
half od pop will usually need > EAR. half will need less.
what is the LRNI
Lower Reference Nutrient Intake (LRNI)
Will meet the needs of 2.5% of the whole population.
Situated 2 SD below EAR.
LRNI equivalent to 1969 RDI.
In many countries LRNI is only figure used.
what is the RNI
Will meet the needs of 97.5% of the whole population.
Situated 2 SD above EAR.
RNI includes margin of safety – individuals with intake just below RNI may have sufficient intake.
if nutrient intake is greater then RNI then the individuals intake can be classed as
almost certainly adequate
if individuals intake is <EAR and < RNI then their intake can be classes as
likley to be adequate
If intake is > LRNI and < EAR then the individuals intake can be classed as
likely to be inadequate
If intake is < LRNI then individuals intake can be classed as
almost certainly inadequate for most individuals
why can we say someone is deficient if they’re nutrient intake is below the RNI and even well below the EAR
as it may be sufficient to their needs
If mean for group is around the RNI most subjects should be what
okay
if mean for a group is around the EAR then subjects might be what
all subjects might be OK but more likely some will not be.
If mean for a group is at the LRNI then subjects will what
not have enough
why can RNIs for all nutrients (not energy) can be set at the upper range of requirements
as an intake moderately in excess of requirements has no adverse effects, but decreases the risk of deficiency.
what is the only measurement given for energy intake
EAR
what do individual requirements of energy depend on and why
BMR and PAL
cos these are the main components of energy expenditure
what is total energy expenditure equal to
BMP times PAL
wheres excess energy stored
in adipose tissue
a BMI between what is the ideal weight range
18.5 and 24.9
in 2011 BMR predicted using healthy reference body weights, so what did this do to people overweight who followed the recommended amount
they lost weight
how do we estimate BMR
measure our energy expenditure using calorimetric methods and we can estimate it using equations
Can calculate without height but it gives an added level of accuracy
there is no absolute requirement for what fats and carbs
fats, sugars or starches.
except for the essential fatty acids:
(linoleic acid (n-6) – sunflower, corn oil
Alpha-linolenic acid (n-3) – linseed, canola, soybean oil)
Panel on DRVs made judgements based on the changes from current intakes that would be expected to result in certain changes in what
physical and/or heath outcomes
for fat and carbs DRVs are given as… and how are they expressed
as population average, individual minimum and individual maximum.
And expressed as percentage of our energy intake rather than grams per day
DRVs for fat are based on change in what
serum cholesterol needed to decrease CHD risk.
what is safe intake
A level or range of intakes at which there’s no risk of deficiency and below a level where there’s a risk of undesirable effects.
when is safe intake used
when not enough info to determine an LRNI, EAR or RNI
for carb and fat requirements what 3 terms are used
individual minimum
individual maximum
population average
why do we just have a safe intake for vitamins C and K recommendations
cos Some nutrients known to be important but there’s insufficient data on human required to set any DRVs
what are DRVs for fat expressed as
% total E (% food energy)
what do food energy sources include
that from protein, fat and carbs
what do total energy sources include
energy from protein, fat, carbs and alcohol
what does the total fat recommendation include
fatty acids and glycerol
DRVs for carbs are expressed as what
% total dietary energy
how were DRVs derived
Panel looked at, Observed intakes in populations without deficiency or excess.
Intakes known to match known losses or physiological requirements in healthy subjects (e.g. pregnancy, lactation, iron loss in menstruation).
Intakes associated with optimal level of some biological function. E.g. degree of enzyme saturation
Intakes which have been shown to cure deficiency (e.g. Vitamin C). 10mg/d sufficient to cure clinical signs of scurvy.
what are limitations of DRVs
Often derived from experimental data limited to
certain groups (e.g. young men rather than women, healthy individuals ).
Limited info on certain groups e.g. children and elderly, or people w diseases.
Usually committees add a safety margin – varies between countries. E.g vit C varies between uk and usa
For some nutrients, where little is known about requirements, a safe level is given.
Requirements are a best guess!
Need to be updated every 10-15y to include new evidence.
what causes variation in nutrition requirements between individuals
Age, sex, body size (Men have greater req due to body size & activity, except iron as they don’t menstruate)
Physiological state (e.g. infection, pregnant or breastfeeding women)
Digestion & absorption. E.g some people are lactose intolerant
Nutrient losses (e.g. amount of iron lost during menstruation)
Lifestyle (smoking, exercise, exposure to sunlight) e.g. Smokers have increased turnover of vit C + have increased req.
Interactions between nutrients. E.g. iron absorption inhibited by calcium
Drug-nutrient interactions. e.g Warfarin – drug given to people at risk of thrombosis but blocks action of vit K. (blood clotting).
Variations in physiological function
reference intakes (RI) have replaced what on food labels
GDAs - guideline daily amounts was developed to communicate the Government’s recommendations.
have same principle now
what were food labels initially set for
fat, SFA, salt, sugar and fibre in g/day for men and women.
why do we need a balanced nutrient intake
to estimate requirements for certain nutrients where body pool remains constant: average daily loss of nutrient should balance intake.
Intake = Output
Intake < Output ….then intake inadequate.
who are the Scottish dietary goals used by
Used by researchers and health promoters and policymakers and stakeholders who influence the diet of the population
what are the Scottish dietary goals based on
DRVs
