Micronutrients are essential
for life and are distinct from macronutrients (carbohydrate, protein and
fat) in that they are only required in tiny amounts.
An alternative method of
classifying nutrients as either type I or type II has recently been proposed
(Golden, 1995). This classification is based on the way in which the body
responds to a nutrient deficiency. A type I response is characterised by
specific physical signs of deficiency as a result of a reduced tissue concentration
of the nutrient. For example, if the diet is deficient in a type I nutrient
such as iron, there is an initial consumption of body stores followed
by clinical signs characteristic of iron deficiency. The concentration
of iron in the tissues is markedly reduced, but there is no effect on growth
or body weight. In contrast, a type II response is characterised by reduced
growth rate or weight loss in the absence of specific deficiency signs.
For example, if the diet is deficient in a type II nutrient like zinc,
growth stops, followed by weight loss. The concentration of zinc in the
major tissues remains normal and their are no deficiency signs. Protein
and energy (derived from carbohydrates and fat) are classified as type
The type I and II classification
is important because it emphasises that poor growth is not caused solely
by protein-energy malnutrition but can result from other nutrient deficiencies
which may not be recognised and so appropriately treated. Furthermore,
it demonstrates the importance of a wide range of nutrients in causing
poor growth or weight loss, and therefore the need for a nutritionally
are widespread in developing countries and affect approximately 2 billion
people worldwide which is equivalent to one-third of the total world population.
The most common deficiencies are due to lack of iron (anaemia), vitamin
A (xerophthalmia) and iodine (goitre and cretinism). Outbreaks of deficiency
disorders, which are rarely seen in normal circumstances, have also occurred
in emergencies among populations entirely dependent on food aid. These
include deficiencies of vitamin C (scurvy), niacin (pellagra) and thiamin
(beri-beri). The general ration provided in emergencies by agencies like
WFP and ICRC are frequently lacking in some essential micronutrients,
which means that populations always require other foods (or in some cases
micronutrient supplements) to complement the ration. Donor agencies can
assist populations to maximise their intake of micronutrient-rich foods
by adopting a number of different strategies which, in preferred order,
include: promoting the production of vegetables and fruit; providing fresh
food items in the ration; adding a food to the ration which is rich in
a particular vitamin or mineral; providing fortified foods; and supporting
the distribution of nutrient supplements.
| Micronutrient Deficiency
||Anaemia can be
caused by lack of iron, folate or vitamin B12. It is difficult to diagnose
accurately from clinical signs which include pallor, tiredness, headaches
caused by thiamin deficiency. There are many clinically recognisable syndromes
including wet beri-beri, dry beri-beri and infantile beri-beri.
by foamy accumulations on the conjunctiva, that often appear near the outer
edge of the iris, and caused by vitamin A deficiency.
and physical disability which occurs in the offspring of women with severe
iodine deficiency in the first trimester of pregnancy.
||Swelling of the
thyroid gland in the neck caused by iodine deficiency.
||IDDs cover a
range of abnormalities including goitre and cretinism.
see well in the dark or in a darkened room. An early sign of vitamin A
||Pellagra is caused
by niacin deficiency which affects the skin, gastro-intestinal tract and
nervous systems and is sometimes called the 3Ds: dermatitis, diarrhoea
||Rickets is caused
by Vitamin D deficiency and adversely affects bone development resulting
in bowing of the legs when severe.
||Scurvy is caused
by Vitamin C deficiency. Typical signs include swollen and bleeding gums,
and slow healing or re-opening of old wounds.
is caused by Vitamin A deficiency and refers to a range of eye signs including
night blindness, Bitot's spots and corneal ulceration.
||Vitamin A is
a fat-soluble vitamin required for the normal functioning of the visual
system, growth and development, maintenance of epithelial cell integrity,
immune function, and reproduction.
- the synthesis of haemoglobin
(Hb), which carries oxygen to the body's cells.
Is a component of myoglobin
(a muscle protein) and many enzymes.
|- an essential
constituent of hormones produced by the thyroid gland in the neck.
- In the foetus, iodine
is necessary for the development of the nervous system.
|- a water soluble
vitamin, serves a number of essential metabolic functions.
- also assists in absorption
of non-haem iron and is an important anti-oxidant.
and plays a central role in the utilisation of food energy
||- water soluble
and is required mainly during the metabolism of carbohydrate, fat and alcohol.
- necessary for the proper
function of the peripheral nervous system and the heart.
||Retinol is chiefly
found in dairy products, liver and some fatty fish. Carotenes are found
in yellow and red fruits and vegetables, and in green leafy vegetables,
especially the green outer leaves. Vitamin A is absent in vegetable oils
with the exception of red palm oil and fortified margarines.
cereals, vegetables and fruit
Haem- iron: from blood
non-haem iron: from vegetables
|- sea food*
- small amounts in food
dependant on soil iodine content
|- Fresh fruit,
||- meat (offal),
fish, wholemeal cereals and pulses*
- plant and animal foods
|- plant seeds
- all animal and plant tissues
||range of abnormalities
including goitre and cretinism in off spring of deficient mother
prevalence rates to indicate a serious situation
Bitot's spot 0.5%
Corneal xerosis and/or ulceration
30 and above high risks
groups: children and pregnant women
||- no international
standards to indicate what prevalence of vitamin C deficiency is a serious
||- no international
standards to indicate what prevalence of niacin deficiency is a serious
||- no international
standards to indicate what prevalence of thiamin deficiency is a serious
|At risk groups
||- occurs widely
in developing countries with the highest prevalence rates in the regions
of South East Asia and Africa. Children suffering from measles, diarrhoea,
respiratory infections, chickenpox and other severe infections are at increased
risk of vitamin A deficiency
risk groups are:
· Women of child-bearing
· Pregnant and breastfeeding
· Babies exclusively
breastfed beyond the age of 6 months
· Babies given cow's
· Weaning-age children
Regions where malaria and
intestinal parasitic infestation are prevalent.
|- endemic in
many mountainous areas of Europe, Asia, the Americas and Africa where there
is limited access to sea foods.
- prevalence increases with
age and reaches a peak during adolescence.
- affects girls more than
boys and women more than men because of increased activity of the thyroid
gland during pregnancy.
with no access to fruit or vegetables are at risk of deficiency.
- including emergency affected
populations entirely dependent on inadequate rations. Scurvy risk higher
in women (especially pregnant women) than men and increases with age.
|- maize eating
populations, who do not treat the maize to release niacin,
- where legumes, such as
peanuts, have not been provided in emergency rations pellagra has arisen.
- women are at higher risk
than men and risk increases with age.
consume non-parboiled polished rice as a staple are at risk, particularly
where the rice is contaminated with moulds.