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Vitamins

Vitamin solubility, absorption and bioavailability

  • 3 things to know
  • AS 1

Overview

Fat-soluble and water-soluble vitamins, storage and toxicity, antioxidant vitamins, bioavailability, and how preparation, cooking, light and bicarbonate of soda affect vitamin losses.

What you need to know

Answer each one before you reveal it.

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Key term

What is a vitamin?

Key term

Which vitamins are fat-soluble and which are water-soluble?

Key term

How does the body store fat-soluble vitamins compared with water-soluble vitamins?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a vitamin?

    Model answer

    A vitamin is an organic compound needed in tiny amounts for normal metabolism, growth and health. Most vitamins cannot be made by the body in sufficient amounts, so the diet must supply them.

  2. 2

    Which vitamins are fat-soluble and which are water-soluble?

    Model answer

    Vitamins A, D, E and K are fat-soluble. The B vitamins and vitamin C are water-soluble.

  3. 3

    How does the body store fat-soluble vitamins compared with water-soluble vitamins?

    Model answer

    Fat-soluble vitamins are stored in the liver and fatty tissue, so a daily intake is not essential. Water-soluble vitamins are held only in small amounts and the excess is excreted in urine, so they are needed regularly.

  4. 4

    Why are fat-soluble vitamins more likely than water-soluble vitamins to reach toxic levels?

    Model answer

    Fat-soluble vitamins accumulate in the liver and fatty tissue when intake is high. Surplus water-soluble vitamins are mostly lost in urine, so a toxic build-up is less likely.

  5. 5

    Which water-soluble vitamin is an exception to the rule that water-soluble vitamins are not stored?

    Model answer

    Vitamin B12 is stored in the liver. Liver stores of vitamin B12 can last several years, so deficiency develops slowly.

  6. 6

    Describe the general role of the B vitamins in the body.

    Model answer

    Many B vitamins act as coenzymes that help enzymes release energy from carbohydrate, fat and protein. Several B vitamins are also needed for healthy nerves, skin and red blood cells.

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