Vitamin Library

Vitamin A Thiamin B-1 Riboflavin B-2 Niacin B-3
Pantothenic Acid B-5 Pyridoxine B-6 Cobalamin B-12 Biotin
Beta Carotene Bioflavonoid Vitamin C Choline & Inositol
Vitamin D Vitamin E Vitamin K Paba
Vitamin A

DESCRIPTION

Vitamin A occurs in two forms: preformed vitamin A, known as retinol, and provitamin A, known as beta carotene. Vitamin A is known as "the vision vitamin" for its role in aiding eyesight. Vitamin A is fat soluble – it is stored in the liver and need not be replenished every day.

BENEFITS

Vitamin A helps maintain healthy skin, teeth and bones, and mucous membranes in the nose, throat and lungs. It is necessary in the formation of an eye pigment involved in night vision, and is essential for vision in dim light. Vitamin A is needed for proper development of the fetus in the womb.

DEFICIENCY SYMPTOMS

Severe deficiency leads to various physical changes in the eye and will eventually lead to blindness. Marginal deficiency will lead to increased susceptibility to respiratory tract infections and skin problems.

THERAPEUTIC USES

Vitamin A is used successfully in the treatment of certain skin conditions, e.g., acne and psoriasis.

REQUIREMENTS (RNI)

THE RNI VALUES (COMA 1991) FOR VITAMIN A

AGE
AGE

(mcg/day)

(iu/day)
0-12 months 350 1,167
1-6 years 400 1,333
7-10 years 500 1,667
11+ years (female) 600 2,000
11-14 years (male) 600 2,000
15+ years (female) 700 2,333
Pregnancy 700 2,333
Lactation 950 3,167

BEST FOOD SOURCES

Liver, carrots, milk, margarine and butter

RETINOL

FOOD

(mcg/100g)

(iu/100g)

Halibut liver oil

900,000

3,000,000

Lamb’s liver

19,900

66,333

Cod liver oil

18,000

60,000

Butter

985

3,283

Margarine

800

 2,667

Cheese, cheddar

363

1,210

Eggs

190

633

Pig’s kidney

160

533

Milk

56

187

Mackerel

45

150

Beef

10

33

Sardines, canned

7

23

WHO MAY NEED TO SUPPLEMENT

Vegetarians, diabetics (who cannot efficiently convert beta carotene into vitamin A). Those with fat malabsorption syndrome. Those with other impaired absorption conditions, e.g., coeliacs or gastrectomy patients.

SAFETY

Taken in excess, vitamin A can lead to toxicity because it is stored in the liver. However, it still has a high safety margin in that regular daily intakes generally have to exceed 7,500mcg (25,000iu) in women, and 9,000mcg (30,000iu) in men, before toxic side effects are experienced. The vitamin A intake of pregnant women or women likely to become pregnant, should not exceed 3,300mcg (11,000iu) per day; (combined from food and supplements) unless directed. The effects of vitamin A excess would take the form of skin scaling, joint pains, liver enlargement and nausea. Vitamin A toxicity is usually fully reversible.

INTERACTIONS & CONTRAINDICATIONS

Vitamin A and vitamin D are found together in many food sources, although they are not actually dependent upon one another for their absorption or utilization. A deficiency of the mineral zinc can affect the function of vitamin A and vice versa. Vitamin A should not be taken with vitamin-A-derivative acne drugs. The need for vitamin A is decreased if you are on the contraceptive pill.