Week 5 – Micronutrients
Micronutrients can be divided into two main categories:
- Vitamins
o Fat soluble (A, D, E and K)
o Water soluble (C and all the 8 B-vitamins)
- Minerals
o Major minerals
o Trace elements
Micronutrients: because only small amounts are needed less than 1 g/day
they do not provide energy
Main difference between vitamins and minerals:
Vitamins are organic molecules, and minerals are inorganic molecules.
Organic means that they contain carbon atoms.
Vitamins:
From a chemical perspective: organic molecules, so containing carbon atoms
From a nutritional perspective: compounds required in small amounts to ensure normal
metabolism, growth and physical well-being.
Vitamins are essential components of our diet. An insufficient intake of a vitamin may lead to
a specific deficiency syndrome.
There are nowadays 13 groups known as vitamins.
Members of the same vitamin family are called vitamers. E.g. the term vitamin E refers to
compounds that resemble tocopherol and tocotrienol.
Provitamin is a compound that can be converted within the body to a vitamin.
E.g. certain carotenoids can be converted in active form of vitamin A called retinol.
Why distinguish fat- and water-soluble vitamins:
1. Fat-soluble vitamins are more stable to heat than the B-vitamins, and they are less
likely to be lost during processing and cooking of foods.
2. The fat-soluble vitamins are absorbed from the intestine along with fats in foods.
3. Fat soluble vitamins are first absorbed in lymph system and then into the blood, where
water-soluble vitamins move directly into the blood after absorption.
4. Fat-soluble vitamins are not soluble in blood, and therefore require specific carrier
proteins to transport them through the body.
5. Water-soluble vitamins are poorly retained by the body and any excess will be
excreted via the urine. Fat-soluble are not because they are not soluble in urine. Fat-
soluble vitamins are stored in the body, mainly in liver and fatty tissue until they are
, needed because of this storage, fat-soluble vitamins can be eaten once in a while
where water-soluble vitamins need to be eaten more regularly.
Drawback of storage of fat soluble vitamins may lead to toxicity, especially for vitamin A.
Exception of rules: Vitamin B12 is water-soluble but is retained in the body quite well.
The sharing features of the B vitamins:
- Water soluble
- Containing nitrogen as part of chemical structure
- Present in relatively large amounts in the liver
Minerals
There are 118 chemical elements known in the periodic table but only 21 are essential for
our diet.
After deducting the organic molecules: carbon, hydrogen, nitrogen and oxygen 17
elements are left which will comprise the dietary minerals.
Major mineral: when present in body in excess of 5 grams.
including (in order of abundance): calcium, phosphorus, potassium, sulfur, sodium,
chloride and magnesium.
Trace elements: iron, zinc, copper, manganese, molybdenum, fluoride, cobalt, iodine,
selenium and chromium.
Essential elements can be toxic when taken in excess.
Bioavailability: extent to which ingested minerals or other food components are absorbed and
thereby available to the body.
minerals are bound to compounds in the food that limit their absorption.
In general, plant foods have lower mineral bioavailability as compared to animal foods. This
because of:
- Chemical form of the food complex
- Plant foods are rich in negatively charged compounds that tightly bind cations
e.g. phytates, polyphenols, oxalate and dietary fiber
- Low mineral bioavailability may be caused by pre-treatment of a food as result of
processing
Minerals are present in almost all foods exceptions: vegetable oils and table sugar.
RDA in the USA and Canada is called the Dietary Reference Intake (DRIs).
In the UK and by European Food Safety Authority it is called Dietary Reference Values
DRVs.
DRIs include:
- Estimated Average Requirement (EAR): average requirement of half of the healthy
people
- Recommended Dietary Allowance (RDA): intake to meet the requirement of nearly all
healthy people.
Micronutrients can be divided into two main categories:
- Vitamins
o Fat soluble (A, D, E and K)
o Water soluble (C and all the 8 B-vitamins)
- Minerals
o Major minerals
o Trace elements
Micronutrients: because only small amounts are needed less than 1 g/day
they do not provide energy
Main difference between vitamins and minerals:
Vitamins are organic molecules, and minerals are inorganic molecules.
Organic means that they contain carbon atoms.
Vitamins:
From a chemical perspective: organic molecules, so containing carbon atoms
From a nutritional perspective: compounds required in small amounts to ensure normal
metabolism, growth and physical well-being.
Vitamins are essential components of our diet. An insufficient intake of a vitamin may lead to
a specific deficiency syndrome.
There are nowadays 13 groups known as vitamins.
Members of the same vitamin family are called vitamers. E.g. the term vitamin E refers to
compounds that resemble tocopherol and tocotrienol.
Provitamin is a compound that can be converted within the body to a vitamin.
E.g. certain carotenoids can be converted in active form of vitamin A called retinol.
Why distinguish fat- and water-soluble vitamins:
1. Fat-soluble vitamins are more stable to heat than the B-vitamins, and they are less
likely to be lost during processing and cooking of foods.
2. The fat-soluble vitamins are absorbed from the intestine along with fats in foods.
3. Fat soluble vitamins are first absorbed in lymph system and then into the blood, where
water-soluble vitamins move directly into the blood after absorption.
4. Fat-soluble vitamins are not soluble in blood, and therefore require specific carrier
proteins to transport them through the body.
5. Water-soluble vitamins are poorly retained by the body and any excess will be
excreted via the urine. Fat-soluble are not because they are not soluble in urine. Fat-
soluble vitamins are stored in the body, mainly in liver and fatty tissue until they are
, needed because of this storage, fat-soluble vitamins can be eaten once in a while
where water-soluble vitamins need to be eaten more regularly.
Drawback of storage of fat soluble vitamins may lead to toxicity, especially for vitamin A.
Exception of rules: Vitamin B12 is water-soluble but is retained in the body quite well.
The sharing features of the B vitamins:
- Water soluble
- Containing nitrogen as part of chemical structure
- Present in relatively large amounts in the liver
Minerals
There are 118 chemical elements known in the periodic table but only 21 are essential for
our diet.
After deducting the organic molecules: carbon, hydrogen, nitrogen and oxygen 17
elements are left which will comprise the dietary minerals.
Major mineral: when present in body in excess of 5 grams.
including (in order of abundance): calcium, phosphorus, potassium, sulfur, sodium,
chloride and magnesium.
Trace elements: iron, zinc, copper, manganese, molybdenum, fluoride, cobalt, iodine,
selenium and chromium.
Essential elements can be toxic when taken in excess.
Bioavailability: extent to which ingested minerals or other food components are absorbed and
thereby available to the body.
minerals are bound to compounds in the food that limit their absorption.
In general, plant foods have lower mineral bioavailability as compared to animal foods. This
because of:
- Chemical form of the food complex
- Plant foods are rich in negatively charged compounds that tightly bind cations
e.g. phytates, polyphenols, oxalate and dietary fiber
- Low mineral bioavailability may be caused by pre-treatment of a food as result of
processing
Minerals are present in almost all foods exceptions: vegetable oils and table sugar.
RDA in the USA and Canada is called the Dietary Reference Intake (DRIs).
In the UK and by European Food Safety Authority it is called Dietary Reference Values
DRVs.
DRIs include:
- Estimated Average Requirement (EAR): average requirement of half of the healthy
people
- Recommended Dietary Allowance (RDA): intake to meet the requirement of nearly all
healthy people.
