AREC 365 (Exam 1)

lecture 3,

undernutrition: a four part problem

what is it, how much of undernutrition exists, what are its consequences on the invidivdual/society, how do we deal with it

what is it (defining the problem)

science

how much of undernutrition exists + what are its consequences

science and social science

how do we deal with it

policy

first thing to think about when asking “what is it”

substance obtained from food that contributes to mental or physical health or growth

6 categories fo nutrients

Carbohydrates

• Fat

• Protein

• Vitamins

• Minerals

• Water

overnutrition

person consumes too many calories (not a bug problem in developling countries)

dietary deficiency

micronutrient deficicency

• vitamin A, Iodine, Iron and Zince

• main focus of lecture 3

• can be targetted with supplements, vitamins, etc.

micronutrient deficiency - problems that need to be addressed

• a lot of people in the developing world grow their own food, so its difficult to get them the proper nutrients because they arent just buying foods injected with the supplements

• people don’t know if their deficient

how can micronutrients be supplied ? what are the pros? is it a problem?

•Can be supplied through vitamin supplements

(“iodized” salt), food fortification

•Relatively inexpensive and EASY TO ADDRESS WITH SUPPLEMENTS

•Not a problem of “production and supply” of food

undernutrition (type 1)

macronutrient deficiency / protein-calorie deficiency

also known as PEM

links directly to the world food problem, because these are obtained through FOOD, PROTEINS AND CALORIES

undernutrition (type 2)

secondary malnutrition - cant absorb the food you eat

is it easy to tackle micronutrient deficiency?

• it was thought so because they are cheaper to produce

• but progress has not been smooth

energy and its involuntary functions

• breathing, blood circulation, digestion, maintaining muscle

• physcial and mental activity

• fighting disease

• growth

protein - what are the main sources, and what is the nutritional role of proetin

main sources: milk, meat, eggs

role:

• building cells, antibodies

• carry oxygen

• carry nutrients

• work as enzymes for digestion

• HUMAN GROWTH

how are calories created?

via photosynthesis and are very available in plants

how are proteins created

• harder to create than calories

• nitrogren in the air is “fixed” by bacteria in the soil to create amino acids

amino acids - how many are there and how much are in food

20 amino acids

• our body makes 11

• 9 we get from food

animal / plant products - what amino acids do they have

animal products - they have all 9 “complete proteins”

plant - missing some / low in concentration

not “complements” - we need all of them

diets in developing countries are more likely to fufill PROTEIN or CALORIE requirements?

protein! so to solve under nutrition, we need MORE FOOD

main source of energy/calories

• carbohydrates (rice, bread)

• fats (meats, oil)

• proteins give use some energy

protein consumption vs heights

• studies show that more protein - male heights increase acorss the world

• does this imply a casual relationship?

• what else could be going on here?

big question of lecture 3

how large are the society-wide impacts of better nourishment (the SECOND PART of the 4-part problem)

how to measure undernourishment

clinical assement (only useful for advanced undernutrition)

biochemical assessment (precise but $$)

dietary assessments - what are they and how are they completed and what can be a problem

done via SURVEYS (asks people about what they ate)

• calorie/protein content of food is calculated

• some loss of precision in conversion from food item to nutrient

• subject to “recall bias” based on what people remember correctly

solution ot dietrary assessments

have an enumerator record what you eat (they watch you) - but may suffer from the experimenter demand effect

hawthorne effect / experimenter demand effect

people may change behavior because they are being observed

anthropometric assessment

“science of measuring the human body and its parts”

• human body SIZE is linked to MACRONUTRIENT INTAKE

3 measures of undernutrition

wasting, stunting and underweight

wasting

low weight for height

Reflects current/acute undernutrition

• Think famines

stunting

low height for age

• Reflects long-run undernutrition (often maternal)

• Vietnam – children born during war are shorter

than those born before

underweight (low weight for age)

Reflects a little bit of chronic and a little bit of current

• Why?

• You could be short and thus underweight

• You could be in a famine and also underweight

why is anthropometry used so commonly?

• Inexpensive to measure age, height, weight

• Does not require level of training required

for clinical diagnosis

• No recall bias or Hawthorne effect

• Reflects both short-run and long-run undernutrition

heights: nature vs nurture

Bit of both!

• Nature – what is the maximum potential height of person?

• Nurture – how likely is it that a person will achieve that height?

How do we know what appropriate heights and weights are?

measurement is done as a comparison in 3 steps

step 1 of measurement

measure anthropometric indicator of invididuals

step 2 of measurement

Compare with a “reference group”:

• Averages across similar people (age, gender ethnic group)

• The reference group is our “standard”

• Make sure that these groups are correctly selected

step 3 of measurement

Determine based on the difference

• How do we determine how different is worth worrying about?

percentiles

if someone is in the 75th/100 group, that your in the 75th percentile (meaning you are ABOVE 3-quarters of the other people, or than 3-quarters BELOW her)

growth chart percentiles

normal distribution between heights and % of people of that height

z-score slides

• find the mean

• find the standard deviation (Say its 2 cm)

  • flatter the curve, the higher the SD

  • 1 sd = 2 cm away from the mean on both sides, etc.

z-score formual

[x-(Mean)] / (Standard Deviation)

normal distribution and standard deviations

who classifies for under nutrition in terms of z-scores

a) -1 to -2: Mildly undernourished

(b) -2 to -3: Moderately

undernourished

(c) -3 and beyond: Severely

undernourished

z-score changes

how much should we eat to be healthy?

• measure how much you can eat

• see what the reference population (aka healthy population) eats and see where you fall

how much you eat depends on:

• What your current height/weight/age is

  • How much you exercise

  • How good your metabolism is

reference population variation

• Different persons have different levels of each in the reference population

• Once more, we have a “distribution” of how much the reference

population eats

RDA

recommended dietrary allowance

• the amount of food required to keep 97.5 of the population nutrition satisifed

how to calculate RDA

• Basically, plot the distribution of how much reference population eats

• Pick the amount of food that will satisfy all but the top 2.5%

• If you are eating above that amount, you are likely to be

over-eating

EAR

estimated average requirement

the amount fo food required to keep half the population nutrition satifisfied

calculaing ERA

• Calculate the mean food intake of the population

• If you are eating above this mean, you are probably eating enough

• If you are eating WAY below this mean, you may be undernourished

measuring nutritional status of large groups

• nationally representative sample survyes

• look at mass undernutrition indicators

• create “food balance sheets”

• “food balance sheets”

• Look at the total supply of food items in a country

• Production, existing buffers, net imports

• Estimate calorie/protein supply per person per day

The main type of undernutrition to worry about from the food problem’s perspective is

protein- energy malnutrition

The best way to measure undernutrition is via

anthropometric measures

All measurement relies on defining

appropriate reference groups and then comparing with those