Lesson E1 - Vitamins

Question 1

What is a vitamin?

Answer 1

A vitamin is a substance essential for the maintenance of normal metabolic functions, but is not
made in the body and therefore must be provided from an outside source

Question 2

How were vitamins discovered?

Answer 2

Vitamins were discovered by studying several deficiency diseases.

Question 3

water soluble vitamins are

Answer 3

vitamin C and eleven vitamins in the B group

Question 4

fat soluble vitamins are

Answer 4

A, D, E and K)

Question 5

Are vitamins drugs?

Answer 5

When a healthy person obtains vitamins from a healthy diet, we do not consider the vitamins in
the food as drugs. However, when vitamins are consumed in the chemically pure form as a
tablet, they are considered to be drugs.

Question 6

DRIs

Answer 6

Dietary recommended intakes.

Question 7

EAR

Answer 7

Estimated average requirement.

Question 8

RDA

Answer 8

Recommended daily allowance.

Question 9

AI

Answer 9

Adequate intake

Question 10

UL

Answer 10

Upper limit

Question 11

Vitamins are required as dietary supplements in the following situations:

Answer 11

1. Inadequate intake:

(a) Individuals who consume an inadequate diet for reasons of poverty and/or geography. A
good example is the aboriginal people living in the Canadian north.

(b) Individuals consuming a diet consisting of one major food. An example is black groups in
South Africa living on a corn diet.

(c) Individuals consuming an eccentric diet due to a psychiatric disturbance.
(d) Individuals who have particular ideas leading to an idiosyncratic diet.
(e) Individuals who, for religious reasons, consume an inadequate diet.

(f) Alcohol-dependent individuals who have an inadequate food intake since they obtain a
large number of calories from alcohol.

(g) Individuals on restrictive diets.
(h) Individuals on restricted diets for disease management.

Question 12

Vitamins are required as dietary supplements in the following situations:

Answer 12

2. Disturbances in absorption:
   (a) Prolonged diarrhea.
   (b) Liver disease.

(c) An individual taking antibiotics that alter intestinal bacteria. Vitamin K and biotin (one of
the vitamin B group) are derived from intestinal bacteria.

Question 13

Vitamins are required as dietary supplements in the following situations:

Answer 13

3. Increased tissue requirements:

In healthy individuals:
(a) During growth.

(b) During periods of hard physical work, e.g. working deep underground in a gold mine
under hot and humid conditions.

(c) Pregnancy, lactation (breast feeding), menstruation.
(d) Stress.

Question 14

Vitamins are required as dietary supplements in the following situations:

Answer 14

In illness:

(a) Hyperthyroidism (overactive thyroid).
(b) Fever.
(c) Tissue wasting.

Question 15

Consequences of excessive intake of vitamins:

Answer 15

Nutritional approach: This is the rational approach where one selects a diet aimed at
supplying the RDA for each vitamin or a multivitamin preparation which supplies the RDA of each vitamin.

Megavitamin approach: This approach is based on the delusion that “if a small dose is
good, a larger dose must be better.”

Question 16

Mechanism of action and results of deficiency:

Answer 16

Cells are held together in organs by a framework of collagen and intercellular ground substance. Collagen and intercellular ground substance require vitamin C for their formation. If adequate
vitamin C is not provided, then cells will not be held together adequately. Thus, a defect in the
framework holding cells together in blood vessels leads to bleeding. These conditions are associated with severe vitamin C deficiency, namely scurvy.

Question 17

The B group of vitamins, traditionally consisting of eleven members, are grouped in a single
class because they were originally isolated from the same sources, namely liver and yeast. Some
of the B vitamins and their RDA’s are

Answer 17

Folate 200 μg 
Niacin (vitamin B3) 19 mg 
Riboflavin (vitamin B2) 1.7 mg 
Thiamin (vitamin B1) 1.5 mg 
Pyridoxine (vitamin B6) 2.0 mg 
Cyanocobalamin (vitamin B12) 2.0 μg 
Biotin 30-100ug Ranges of 
recommended intakes Pantothenic acid (vitamin B5) 4-7 mg

Question 18

Folate:

It has been shown to be important to supplement the diet of

Answer 18

women of childbearing age with 400
μg of folic acid per day. The reason for the supplement is the demonstration that such a
supplement can markedly decrease the incidence of neural tube defects (such as spina bifida) in
their offspring.

Question 19

Vitamin A: Effects of deficiency:

Answer 19

(a) Growth and development will be retarded.

(b) Vitamin A is a constituent of a complex molecule, called rhodopsin, in rods of the eye, and
is required for night vision. Deficiency of vitamin A leads to night blindness and to drying
of the surface of the eye, a condition called xerophthalmia (dry eye). When deficiency is
severe, visual impairment and blindness may result.

(c) Deficiency of vitamin A leads to changes in cells lining the bronchioles in the lung and
enhances the opportunity for respiratory infection.

(d) Deficiency of vitamin A leads to a dry, thick and horny skin.

Question 20

Vitamin A: Therapeutic Uses

Answer 20

(a) Treatment of vitamin A deficiency. Vitamin A deficiency is a serious nutritional deficiency
disease. It is particularly common in South East Asia, Africa, Central and South America,
and the Middle East, resulting in irreversible blindness in approximately one-quarter
million children per year. Obviously extreme poverty is a major reason.

(b) Administration in periods of increased requirement such as infancy, pregnancy and
lactation.

(c) Vitamin A derivatives are used in the treatment of acne and some other skin diseases

Question 21

Prior to the discovery of vitamin D, a high percentage of urban children, especially those living
in temperate zones, developed

Answer 21

rickets

Question 22

Vitamin D undergoes
conversion in the liver to 25-hydroxyvitamin D, which in turn is converted in the kidney to the
active form of the vitamin, namely

Answer 22

1,25-dihydroxyvitamin D.

Question 23

Actions of vitamin D:

Answer 23

(a) Increases the absorption of calcium and phosphate from the intestine. The calcium and
phosphate is utilized for formation of new bone.

(b) The blood calcium level must be maintained within prescribed limits for optimal health and
vitamin D is involved in regulation of the blood calcium level.

(c) Vitamin D is involved in removal of calcium from older bone.

Question 24

Results of vitamin D deficiency:

Answer 24

(a) Decreased absorption of calcium and phosphate from intestine.
(b) Decrease in blood calcium level.

(c) Calcium removed from bone in attempt to maintain blood calcium level. As a result,
defective bone growth occurs in infants and children leading to bowleggedness – a
condition referred to as rickets. Rickets also occurs in adults.

Question 25

Vitamin E deficiency was found to lead to

Answer 25

muscular dystrophy (degeneration)

Question 26

Vitamin E deficiency is associated with anemia in several animal species. Vitamin E has been
found to be useful in the treatment of premature babies with an uncommon type of

Answer 26

hemolytic anemia.

Question 27

Vitamin E deficiency leads to heart

Answer 27

muscle degeneration