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Nutrition and Health: Micronutrients and Malnutrition Summary Module 1-4
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MOOC UndernutritionContents
Dietary References intakes (DRI).........................................................................................................4
Estimated Average Requirement (EAR)...............................................................................................5
Recommended Dietary Allowances (RDA)...........................................................................................5
Adequate Intake (AI)............................................................................................................................5
Tolerable Upper Intake Level (UL).......................................................................................................6
Additional information on Dietary Reference Intakes .........................................................................6
Dietary supplements................................................................................................................................6
Harm of Supplements..............................................................................................................................6
Module 2................................................................................................................................................6
Dehydration.............................................................................................................................................8
Sodium and potassium............................................................................................................................9
Salt restriction programs...................................................................................................................10
Function.............................................................................................................................................11
Blood pressure...................................................................................................................................11
Vascular calcification.........................................................................................................................11
Obesity...............................................................................................................................................11
Iron........................................................................................................................................................12
Absorption.........................................................................................................................................12
Storage...............................................................................................................................................12
Function.............................................................................................................................................13
Health effects of iron.........................................................................................................................13
Iodine.....................................................................................................................................................14
Iodine deficiency................................................................................................................................14
Other food sources............................................................................................................................14
Selenium................................................................................................................................................14
Function in the body..........................................................................................................................14
Proteins and zinc....................................................................................................................................15
Module 3..............................................................................................................................................16
Vitamin A...............................................................................................................................................16
Forms of vitamin A in the body..........................................................................................................16
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, Food sources and DRI of vitamin A....................................................................................................16
Functions of vitamin A...........................................................................................................................17
Vitamin A in vision.............................................................................................................................17
Vitamin A deficiency and toxicity.......................................................................................................18
Vitamin D...............................................................................................................................................18
Functions of vitamin D.......................................................................................................................19
Vitamin D deficiency and toxicity.......................................................................................................19
Measuring vitamin D..........................................................................................................................20
Vitamin E................................................................................................................................................20
Vitamin E deficiency and toxicity.......................................................................................................21
Vitamin K...............................................................................................................................................21
Vitamin K deficiency..........................................................................................................................21
Module 4 Water-soluble vitamins........................................................................................................22
Vitamin C deficiency and toxicity.......................................................................................................23
Folate.....................................................................................................................................................23
Metabolism........................................................................................................................................24
Vitamin B12...........................................................................................................................................25
The remaining B vitamins......................................................................................................................26
Thiamin (vitamin B1)..........................................................................................................................26
Riboflavin (vitamin B2).......................................................................................................................26
Niacin (vitamin B3).............................................................................................................................26
Pantothenic acid................................................................................................................................27
Vitamin B6.........................................................................................................................................27
Biotin.................................................................................................................................................27
Module 1
Micronutrients: Need to consume less than 1 gram per day
- Essential Minerals: (inorganic molecules= does not contain carbon) Rock
- Major minerals
Present in body in excess of 5g
In order of abundance: calcium, phosporus, potassium, sulfur, sodium, chloride
and magnesium
- Trace elements
iron, zinc, copper, manganese, molybdenum, fluoride, cobalt, iodine, selenium
and chromium
- Vitamins (organic molecule= contains carbon atom) Organisms
- Fat soluble vitamins (vit: A, D, E, K)
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, - More stable to heat, less likely to be lost during cooking
- Absorbed in intestine along with fats
- Absorbed into the lymph system and then into the blood
- Not soluble in blood (need carries molecules)
- Stored in the body (liver and fatty tissue)
- Water soluble vitamins (vit. B + C)
- Poorly retained by the body excreted via the urine
- Need to be eaten regularly (no storage), but less likely toxic
- Exception: B12 is retained in the body
Insufficient intake may lead to specific deficiency syndrome
Vitamers: Same vitamin family of chemically related compounds with comparable metabolic activities
Provitamin: compound that can be converted within the body to a vitamin
Macronutrients: Need to consume larger quantities, and provide energy
- Essential amino acids
- Fatty acids
Mineral bioavailability
Only a part of the total amount of minerals present in a food is available to the body. That is mostly
because minerals are bound to compounds in the foods that limit their absorption.
Bioavailability: the extent to which ingested minerals or other food components are absorbed and
thereby available to the body.
In low-income countries, a low bioavailability of minerals is a major contributor to poor mineral
status. This situation is mainly observed in people subsisting on monotonous plant-based diets.
Plant foods have a lower mineral bioavailability compared to animal foods. Diet-related factors
in plant foods that affect bioavailability include the chemical form of the nutrient in food and/or
nature of the food matrix. In addition, many plant foods are rich in negatively charged
compounds that tightly bind cations (positively charged elements such as calcium, iron and
zinc) and thus have lower mineral bioavailability. These compounds include phytates,
polyphenols, oxalate, and dietary fiber. Finally, low mineral bioavailability may be caused by
pre-treatment of a food as a result of processing and/or preparation practices.
Dietary minerals are present in nearly all foods. Except in vegetable oils and table sugar. Much
of our calcium intake comes from eating cheese and milk, whereas most of the dietary iron is
obtained via consumption of whole grain products, beans, and meat.
Discovery of Vitamins:
Diseases could be caused when food lacked a substance necessary for metabolism.
The term ‘vitamin’ was coined by Funk in 1912 when he isolated the anti-beriberi factor.
Hopkins established that rats got sick and died when put on diets of pure protein, fat and
carbohydrates. The addition of milk made the difference between life and death for the rats.
McCollum and his coworker Kennedy proposed the terms “fat-soluble A” and “water-soluble B”
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,They found that at least one of these organic dietary essentials was soluble in water,
whereas the other one was soluble in fats.
1920’s and early 1930’
Water-soluble “vitamin B” was in reality a mixture of at least several unrelated vitamins. Thus
the term “vitamin B complex” was devised. The eight B complex vitamins share a number of
features: being soluble in water, containing nitrogen as part of their chemical structure, and
being present in relatively large amounts in the liver, the main metabolic organ in the body. As
the vitamins became differentiated, they were designated by letters of the alphabet, usually in
order of their discovery.
Dietary References intakes (DRI)
The Dietary Reference Intakes (DRI) are based on scientifically grounded relationships between nutrient
intakes and indicators of adequacy, as well as the prevention of chronic diseases in apparently healthy
populations. DRI are established through extensive review processes an d it includes:
- Estimated Average Requirement
o level of intake of a nutrient at which the requirement of half of the healthy people is met
- Recommended Dietary Allowance
o level of intake of a nutrient that is sufficient to meet the nutrient requirement of nearly all
healthy people.
- Adequate Intake
o when there is insufficient data to define a RDA.
- Tolerable Upper Intake Level
4
, o highest level of daily intake of a nutrient that is safe.
Over the last several decades, many people have started to consume vitamins and minerals in
concentrated form, as supplement, driven by the notion that these supplements would prevent disease
and improve health, performance, and longevity. Many of these multi-vitamin and mineral supplements
provide these nutrients at levels way above the RDA. That’s why the RDA in 1997 added an the upper
levels of intake (UL)
Estimated Average Requirement (EAR)
The central question in determining dietary recommendations is how much of a nutrient is
required in the diet of a healthy person. This requirement is based on information in the
scientific literature. The selection criteria for a specific nutrient depend on the biological
function of the nutrient in the body and its role in reducing risk of diseases. It is obvious that
each person’s body is unique and the nutritional needs of men differ from women. Still, the
exact requirements for people of the same gender and age are likely to be different. Looking at
enough people might reveal that their individual requirements fall into a symmetrical
distribution. Therefore, the EAR is more informative at a population level rather than at the
level of an individual.
Recommended Dietary Allowances (RDA)
The next step is to determine Recommended Dietary Allowance (RDA). Since EAR describes the
Estimated Average Requirement, an intake at the level of EAR does not meet the requirements
of all individuals. In fact, about half of the people have an actual requirement that exceeds the
EAR. That’s why recommendations are set at a level higher than the EAR in order to meet the
needs of most healthy people in the population. Intake levels that are slightly higher than the
daily requirement don't do harm, whereas levels lower than the requirement may compromise
health. Therefore, to ensure that the nutrient RDA meet the needs of nearly everybody, the
RDA is set near the top end of the range of the population’s estimated requirements to capture
the needs of about 98 percent of the people. From a statistical perspective, this number equals
the EAR plus 2 times the standard deviation.
Adequate Intake (AI)
For some nutrients such as vitamin K, there is insufficient scientific evidence to determine an EAR, which
is needed to set a RDA. In these cases, the committee establishes an Adequate Intake (AI) instead of a
RDA. An AI reflects the average amount of a nutrient that a group of healthy people consumes. But an
AI, must rely more heavily on scientific judgments, as sufficient evidence is lacking.
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