What are phytates, and how do they affect mineral absorption?

Phytates, or phytic acid, are phosphorus compounds found in wholegrain cereals, bran, pulses, nuts and seeds. Phytates bind iron, zinc and calcium in the gut into insoluble complexes that cannot be absorbed.

What are oxalates, and how do they affect mineral absorption?

Oxalates are compounds found in spinach, rhubarb, beetroot and cocoa. Oxalates bind calcium and iron into insoluble salts, so spinach is a poor source of calcium despite its high content.

How do tea and coffee affect iron absorption?

Tea and coffee contain tannins and other polyphenols that bind non-haem iron and reduce its absorption. Tea and coffee are best drunk between meals rather than with them.

Name the dietary factors that increase the absorption of non-haem iron.

Vitamin C eaten in the same meal is the strongest enhancer of non-haem iron absorption. Meat, fish and poultry eaten in the same meal also increase it.

CCEA A-Level Nutrition and Food Science 3310

Protein

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Minerals

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Minerals

Mineral bioavailability and absorption

3 things to know
AS 1

Overview

Phytates, oxalates, tea and fibre as inhibitors, vitamin C and haem iron as enhancers, factors affecting calcium absorption, mineral competition and body need.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why is the total amount of a mineral in a food a poor guide to how much the body receives?

Key term

Which factors increase the absorption of calcium?

Key term

How can minerals compete with each other for absorption?

Questions from this subtopic

Each one with the model answer underneath.

1
Why is the total amount of a mineral in a food a poor guide to how much the body receives?
Model answer
Only part of the mineral in a food is absorbed, and the proportion varies with its chemical form and the rest of the meal. Absorption also depends on the body's need for the mineral.
2
What are phytates, and how do they affect mineral absorption?
Model answer
Phytates, or phytic acid, are phosphorus compounds found in wholegrain cereals, bran, pulses, nuts and seeds. Phytates bind iron, zinc and calcium in the gut into insoluble complexes that cannot be absorbed.
3
What are oxalates, and how do they affect mineral absorption?
Model answer
Oxalates are compounds found in spinach, rhubarb, beetroot and cocoa. Oxalates bind calcium and iron into insoluble salts, so spinach is a poor source of calcium despite its high content.
4
How do tea and coffee affect iron absorption?
Model answer
Tea and coffee contain tannins and other polyphenols that bind non-haem iron and reduce its absorption. Tea and coffee are best drunk between meals rather than with them.
5
Name the dietary factors that increase the absorption of non-haem iron.
Model answer
Vitamin C eaten in the same meal is the strongest enhancer of non-haem iron absorption. Meat, fish and poultry eaten in the same meal also increase it.
6
Which factors increase the absorption of calcium?
Model answer
Vitamin D is essential for calcium absorption from the gut. Lactose and some amino acids in milk also help, so dairy calcium is well absorbed. Absorption rises when needs are high, as in growth and pregnancy.

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