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Today & next few lectures. Look through & selectively read from the “hunger/nutrition issues” links on Blackboard Today Biology of human nutrition Traditional diets & protein-calorie nutrition Vitamins, minerals, & deficiency diseases Synergies between nutrition & disease Next week

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Today & next few lectures

  • Look through & selectively read from the “hunger/nutrition issues” links on Blackboard

  • Today

    • Biology of human nutrition

    • Traditional diets & protein-calorie nutrition

    • Vitamins, minerals, & deficiency diseases

    • Synergies between nutrition & disease

  • Next week

    • Malnutrition & hunger

    • The Entitlement concept

    • Causes of hunger – the Irish famine example

    • Nutrition transition


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Nutrition and Hunger

  • Biology of Nutrition

    • Active adults and growing children need most food/body weight

    • But, small children, infants, and the aged are most at risk to severe consequences of nutritional problems

    • Nutritional needs

      • Energy: commonly measured in kilocalories (kcal) or what we usually call “calories”

      • Protein: variable in “quality” for human use


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Energy

  • Body “burns” carbohydrates, fats, and sugars for the energy to live

  • Proteins also can be converted by the liver to sugars for energy if necessary, but not vice versa (not very efficient)

  • Calories in excess of need => storage as fat


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Severely Insufficient Nutrition

  • Calorie or protein-calorie malnutrition

    • Severe forms of this in infants especially can lead to marasmus

    • Body breaks down lean muscle and tissue to produce calories

  • Severe protein malnutrition can lead to kwashiorkor


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Marasmus

  • Stick-like limbs, bloated belly, wide eyes:

  • From Greek “to waste away”

  • Lacking calories (as well as protein), children may weight less than half of normal

  • Brings diarrhea, apathy, and brain damage

  • Bloated look as fluids are accumulated to push against wasted muscles.


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Kwashiorkor

  • Severe protein deficiency

  • Bloated body

  • Fluids stuffed in cells against wasted muscles

  • Results in diarrhea, apathy, brain damage


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Protein

  • There are 22 amino acids needed to create the thousands of proteins humans need to create: e.g., blood, hormones, hair, muscle, antibodies, etc.

  • We make all the amino acids needed except for 9 that must be in foods:

    • leucine, valine, tryptophan, phenylaline, isoleucine, threonine, lysine, cystine, and methionine

  • Foods vary in their composition of these so vary in “quality” of protein (% protein that is usable)

  • Foods also vary in total quantity of protein per gram


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“Quality” of protein I

  • Animal foods:

    • Quality is relatively high

      • e.g., eggs = 98%; milk = 80%; fish = 80%; meat = 70%

    • Quantity is relatively high as well

  • Grains:

    • Quality is relatively high

      • e.g., rice, wheat, oats = 70%; millet, rye = 55-60%

    • Quantity is relatively low

      • ~ 10-15% by weight is protein


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“Quality” of protein II

  • Legumes (pulses):

    • Quality is so-so – usually deficient on one or more of the 9 amino acids

      • e.g., soy beans = 60%; lima beans = 50%; lentils = 30%

    • Quantity is relatively high

  • Other vegetables

    • Quality is so-so to poor

    • Quantity frequently low also


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Traditional diets I

  • Traditional Mesoamerican bean burrito

    • Beans

      • Short of methionine, cystine

      • Lots of lots of lysine, tryptophan, isoleucine

    • Corn (maize)

      • Short of tryptophan & lysine (OK otherwise)

    • So the beans balance the shortage of tryptophan and lysine in the corn making the overall protein quality very good


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Traditional diets II

  • Hamburger & wheat bun

    • Wheat

      • Short of lysine

      • Lots of methionine, tryptophan, isoleucine

    • Beef

      • Lots of lysine

    • So the two balance each other out

  • Rice and Soy

    • Rice is short on lysine so mixed with most beans => good

    • Soybeans have lots of lysine and tryptophan so good with rice


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Vitamins & minerals

  • Chronic shortages may not show obvious effects but at the biochemical level there are problems

    • Variety in diet best solution

  • Shortages can be precipitated by some diseases (e.g., parasites such as hook worm, malaria, etc.)


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Historical acute deficiency diseases

  • Beri-beri: thiamine (vitamin B1)

    • Found in rice eating pops in Asia

    • More varied diet => not a major problem now

    • Common vegetable sources are various legumes and whole grains -- polished (white) rice is deficient

  • Pellagra: niacin (vitamin B3)

    • In populations who consume maize or sorghum as main foods since both are low

    • Not in Mesoamerica, however, because of the treatment of maize (nixtamalization) => increases niacin and beans have it as well


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Historical acute deficiency diseases

  • Scurvy: vitamin C

    • Formerly a major problem for sea-going navies and explorers

      • Early 19th C British Navy solution – eating limes => Brits commonly called “Limeys”

      • Sauerkraut also works fine!

    • Periodically a problem in refugee pops who don't get enough fresh fruits and vegetables

  • Rickets: vitamin D

    • Lack of sufficient sunlight in winter


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Contemporary acute deficiency diseases: Iron

  • Iron deficiency:

    • Most common single nutrient deficiency in the world

      • > 1/3 of pop in many developing countries

    • Reduces cognitive performance, energy and work ability, and resistance to infection (especially to diarrheal and respiratory diseases) even in mild cases

    • Severe forms = anemia


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Contemporary acute deficiency diseases: Iodine

  • Iodine deficiency:

    • Iodine is lacking in soils from some mountain areas and in domr highly leached soils

      • e,.g., Andes, Himalayas, C Africa, SE Asia...

    • Major consequences:

      • Swelling of thyroid (goiter)

      • Important mental deficiencies (cretinism) in kids if deficient in pregnant women


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Contemporary acute deficiency diseases: Vitamin A

  • Vitamin A deficiency:

    • Major consequences

      • To vision can lead to blindness

      • Also decreased immune function

      • Kids with severe protein-calorie malnutrition often have impaired sight as a result of this


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Synergy: nutrition and disease

  • Poor nutrition (protein-calorie or other nutrient shortages) => reduced ability to fend off new infections or makes existing ones more severe

  • Diseases interfere with nutrient absorption and/or actively deplete nutrients from our bodies


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How poor nutrition => disease

  • Reduction in the body's innate immunities (that react to general patterns of proteins in pathogens)

    • Less effective phagocytosis (process by which microorganisms are engulfed and encapsulated)

    • Weakened epithelial barriers (protective coverings on body surfaces inside and out)

    • Lowered lysozyme production (a bodily protein that functions as an antibacterial)


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How poor nutrition => disease II

  • Reduction in ability to generate acquired immunities - the specific immunities one acquires to a particular disease pathogen

    • Reduced production of humoral antibodies

    • Impaired cell-mediated immunity


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How disease => poor nutrition

  • Most infections interfere with the body's ability to absorb nutrition and/or actively deplete nutrients

    • Reduced appetite

    • Poorer quality of diet ingested

    • Diseases deplete bodily tissue

    • Fevers => increased metabolic rate thus, the body needs more kcal but they may not be there


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Special case of GI tract diseases

  • 1.8 billion cases/yr of infant/weanling GI diseases

  • Predominantly diarrheas, but also intestinal parasites, cholera, & various types of dysentery

    • Impede absorption of nutrients (diarrheas just don't let food sit in gut long enough)


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Special case of GI tract diseases II

  • Many if not most deaths (perhaps 1 million/ yr in the world) can be averted with adequate treatment (called Oral Rehydration Therapy)

    • According to The Lancet (1978), ORT is "potentially the most important medical discovery of the 20th century"

    • Clean water with 60 cent packets of salts/sugars to recover health

    • Full recovery => increased nutrition above basic levels – often hard to get


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Oral Rehydration Therapy

(packet for addition to water)

Oral Rehydration Therapy

(home made)


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Especially vulnerable populations I

  • Increased likelihood of malnutrition and more serious consequences

  • Women in general due to cultural traditions that privilege food to males

  • Pregnant women

    • Poor nutrition => low birth weight babies

    • Developmental problems for baby physically and mentally

    • Reduced resistance to diseases

    • Less able to breast feed (=> less resistance for the baby as well)


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Especially vulnerable populations II

  • Lactating women

    • Poor nutrition seldom greatly interferes with ability to produce milk

    • But, poor nutrition does deplete the mother's body of necessary nutrients

    • If nutrition is not better between end of lactation and next pregnancy => spiral down to chronic anemia etc.

  • Elderly

    • Ability to fend off infections is reduced with great age and malnutrition hurts that as well


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Especially vulnerable populations III

  • Children

    • Malnutrition in infants and children very problematic if timing coincides with critical growth processes

      • Up to age 5 risk is greatest

    • Especially at weaning age (approx 2 yrs)

    • Due to impure water used to make weaning foods (not sufficiently boiled due to lack of fuel) and general low hygiene =>

      • Kids die from diarrheal diseases and dehydration and malnutrition

    • Weaning foods are typically not nutrient-rich enough (e.g., maize gruels)


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Four Faces of Hunger I

  • I. Starvation/Famine

    • Widespread to complete lack of protein/calorie nutrition

    • A small percentage of global hunger – perhaps 1% at risk annually

    • Leads to increased mortality (usually to infectious diseases not starvation per se)

    • Great social disruption => increased problems with diseases and access to food

    • In any famine not all starve – the well off can buy food -- thus NOT usually only a simple shortage


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Four Faces of Hunger II

  • II. Malnutrition/Undernutrition

    • Seasonal or periodic P/C under-nutrition

    • Most serious effects on kids and special needs adults (pregnant and lactating women, the elderly)

    • measures of malnutrition in children

      • Stunting - stature too short for age/sex (adjusted for local norms) => chronic

      • Wasting – weight too light for age/sex (adjusted for local norms) => acute


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Four Faces of Hunger III

  • III. Micro-nutrient deficiencies

    • Vitamin and mineral shortages

    • Sometimes called “hidden hunger”

  • IV. Nutrition-depleting illnesses

    • Secondary malnutrition

    • Most common nutrient depleting diseases are infant/weanling diarrheas – 5 million deaths annually world wide


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Global Hunger

  • Global situation late 1990s

  • Data drawn from FAO’s SOFA report 2002

  • http://www.fao.org/DOCREP/004/y6000e/y6000e00.htm

  • The International Food Policy Research Institute:

  • http://www.ifpri.org/pubs/fpr/fpr24.pdf

  • The concept of “food security”


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Global Trajectories of Hunger I

  • Proportions undernourished (or food insecure)

    • Late 1970s ~ 28%

    • Late 1990s ~17%

    • Thus, real progress

    • Less progress in absolute numbers

  • Micro-nutrient deficiencies

    • Iron: 40% of global south

    • Iodine: 12% of global south

    • Vitamin A: 14% of kids in global south


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Global Trajectories of Hunger II

  • Absolute numbers undernourished (or food insecure)

    • 1970s ~ 900m; 2000 ~ > 800 m

    • => decrease of ~ 100m in absolute numbers (but smaller %)

  • Children 1993 ~ 200 m; now ~ 175 m

  • World food summit target in 2015 => 400m

    • Current trajectory => 475-500m by 2015


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Regional differences malnourished or food insecure

  • Global South

    • Sub-Saharan Africa

    • E. Asia, SE Asia, & Pacific

    • South Asia

    • Latin America & Caribbean

    • Near East & N. Africa

  • Developed Economies (mostly N America)







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