Vitamin A and beta-carotene

Overview

Retinol and beta-carotene, vitamin A's roles in vision and epithelial tissue, food sources, night blindness and global deficiency, and the risks of excess retinol in pregnancy.

What you need to know

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Questions from this subtopic

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1. 1

   Name the two forms of vitamin A found in the diet.

   Model answer

   Retinol is the preformed vitamin A found in animal foods. Beta-carotene is a carotenoid pigment in plant foods that the body converts into retinol.

2. 2

   How is vitamin A involved in vision in dim light?

   Model answer

   Retinol is needed to make rhodopsin, the light-sensitive pigment in the rod cells of the retina. Without enough rhodopsin the eye cannot adapt to dim light.

3. 3

   Describe the role of vitamin A in maintaining epithelial tissue.

   Model answer

   Vitamin A keeps the mucous membranes lining the eyes, mouth, gut and respiratory tract moist and healthy. Healthy mucous membranes act as a barrier against infection.

4. 4

   Name two functions of vitamin A apart from its roles in vision and in mucous membranes.

   Model answer

   Vitamin A is needed for normal growth and development. Vitamin A also supports a healthy immune system.

5. 5

   Name valuable food sources of retinol.

   Model answer

   Liver is the richest source of retinol. Oily fish, eggs, whole milk, cheese and butter also supply it, and many fat spreads are fortified with it.

6. 6

   Name valuable food sources of beta-carotene.

   Model answer

   Orange and yellow vegetables and fruit are rich in beta-carotene, for example carrots, sweet potatoes, mangoes and apricots. Dark green leafy vegetables such as spinach and kale are also good sources.

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