Introduction

Minerals are the inorganic elements, other than carbon, hydrogen, oxygen and nitrogen, which remain behind in the ash when food is incinerated. They are usually divided into two groups - macrominerals and microminerals (or trace elements). The terms are historical in origin and originated at a time when the development of analytical equipment was still in its infancy and 'trace' was used to refer to components whose presence could be detected, but not quantified. Modern analytical equipment that allows determination of elements at levels in the nano- and even picogram range, can show the presence of most of the minerals in almost any food. Some are present in minute amounts, but others are at significant levels.

The minerals are classified as either essential or non-essential, depending on whether or not they are required for human nutrition and have metabolic roles in the body. Non-essential elements are also categorised as either toxic or non-toxic. Table 4.1 lists elements that occur in food and are important in human nutrition. In addition to the essential elements, some others, including arsenic, silicon and boron, have been shown to be required by certain animals and may also play beneficial roles in the human body.

This section will present an overview of the principal essential minerals, covering their chemical characteristics, basic roles in human health, dietary origins (from food and supplements), and their Reference Nutrient Intakes (RNI), including Safe Intakes (SI). This will be followed by consideration of a number of selected minerals that are of particular interest at the present time. Attention will be given particularly to their nutritional significance, including their possible roles as functional ingredients of food. The elements to be discussed in detail are

Table 4.1 Mineral elements in food

Macrominerals (g/kg)

Microminerals (mg/kg)

Toxic minerals (mg/kg)

Calcium (<1-12) Magnesium (1-4) Phosphorus (1-6) Potassium (1-6) Sodium (1-19) Sulphur (<2-6)

Chromium (<0.02-0.95) Cobalt (0.008-0.32) Copper (<0.2-3.3) Iodine (0.04-0.66) Iron (<0.2-92) Manganese (<0.10-14.0) Molybdenum (0.004-1.29) Selenium (<0.001-0.34) Zinc (0.2-8.6)

Cadmium (0.001-0.07) Lead (0.01-0.25) Mercury (<0.001-0.18)

data from Reilly C (2002) Metal Contamination of Food, 3rd ed. Blackwell science: Oxford.

data from Reilly C (2002) Metal Contamination of Food, 3rd ed. Blackwell science: Oxford.

calcium, iron, and zinc. Two other elements, iodine and selenium, will also be considered, though in less detail. A final section will provide suggestions for further reading.

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