Zinc: Source, functions, RDA, toxicity and metabolism

1. Micromineral
ZINC

2.  Normal healthy adult contains 1.5-2.5g zinc.
 Present in all cells, tissues, organs, fluids and
secretions.
 90% of zinc is in muscle and bone.
 Blood plasma contains 0.1% zinc.
 Zinc plasma level is about 96ug/100ml in adults
and 8.9ug/100ml in children.

3. Functions
 Essential for normal growth, development,
reproduction and immunity.
 Involved in maintaining appetite, assisting in the
perception of taste and for night vision.
 Humans and animals contain about 200 enzymes
whose activity depends on the presence of zinc.
 Considered as an antioxidant nutrient.
 Essential for the metabolism of protein and
nucleic acids.
 Maintenence and replication of DNA and RNA.
 Involved in cholesterol transport and in maintainig
the stability of lipids within the cell membrane.

4. RDA
Group Zinc (mg/day)
Man 14
Woman 11
Pregnancy 12
Lactating 12
Infants -
6-12 months 2
Children
1-3 years 2.5
4-6 years 3.7
7-9 years 4.9
Boys
10-12 years 7
13-15 years 11.9
16-18 years 14.7
Girls
10-12 years 7.1
13-15 years 10.7
16-18 years 14.7

5. Sources
 Zinc status of soil determines the concentration of
zinc in foods.
 FAO rated India ‘low’ in ratings soil for zinc
concentration.
 Oysters – 1mg/g
 Meat, poultry, eggs and dairy products are the best
sources.
 Outer layer of grains also contributes to zinc.
 Nuts contain high amount of zinc.

6. Toxicity
 An acute toxicity with 1-2g of zinc sulphate can
produce metallic taste, nausea, vomiting,
epigastric pain, abdominal cramps and bloody
diarrhoea.

7. Deficiency
 Some of the factors of zinc deficiency are
excessive phytates and phosphates in diet,
malabsorption, hepatitis, chronic blood loss,
trauma, alcoholic liver disease, surgery, burns,
excessive sweating etc.
 Acrodermatitis enteropathica – Disorder of zinc
metabolism. Severe dermatitis appear in the first
few months of an infant’s life, when the infant is
switched from mother’s milk to cow’s milk.

8.  Premature infants and PEM (Protein Energy
Malnutrition) children are susceptible to zinc
deficiency.
 The clinical manifestations include growth
retardation, male hypogonadism (a condition in
which the body doesn't produce enough of the
hormone that plays a key role in masculine
growth and development during puberty
(testosterone) or enough sperm or both) in the
adolescents, rough skin, poor appetite, mental