Mineral and Trace Element Metabolism

Minerals and trace elements are the inorganic micronutrients essential to human metabolism, ranging from macrominerals such as calcium, magnesium, and phosphorus to trace elements such as iron, zinc, copper, selenium, and iodine. They serve as enzyme cofactors, structural components, electrolytes, and constituents of hormones and oxygen-carrying proteins, and the body maintains their concentrations through tightly regulated absorption, storage, and recycling.

Definition

Mineral and trace element metabolism is the study of the absorption, distribution, storage, and physiological roles of the essential inorganic micronutrients, which function as enzyme cofactors, structural elements, electrolytes, and components of metalloproteins and hormones.

Scope

This topic covers the biochemical functions of essential minerals and trace elements, how their body content is regulated, and the metabolic roles of key elements including iron, zinc, copper, selenium, iodine, calcium, and magnesium. It treats mineral metabolism as a biochemical topic and excludes clinical management of mineral disorders.

Core questions

• What biochemical roles do iron, zinc, copper, selenium, and iodine play?
• How is whole-body mineral balance regulated when most trace elements cannot be readily excreted?
• How do macrominerals such as calcium and magnesium differ functionally from trace elements?

Key concepts

• Macrominerals versus trace elements
• Metalloenzymes and metal cofactors
• Iron and oxygen transport / redox catalysis
• Hepcidin-ferroportin regulation of iron
• Zinc in catalysis and gene regulation
• Selenium and selenoproteins
• Iodine and thyroid hormone synthesis
• Magnesium as an enzyme and ATP cofactor

Mechanisms

Trace elements act largely by binding to proteins at catalytic or structural sites. Iron is incorporated into haem and iron-sulphur clusters that enable oxygen transport and electron transfer, and because the body has no regulated route to excrete iron, balance is controlled at absorption by the hepcidin-ferroportin axis (Hentze, 2010). Zinc serves both catalytic and structural roles, including the zinc-finger motifs of transcription factors; copper is a cofactor in oxidases and in iron mobilization; selenium is incorporated as selenocysteine into selenoproteins such as glutathione peroxidases; and iodine is built into thyroid hormones. Among macrominerals, calcium acts as a structural mineral and intracellular signal, and magnesium stabilizes ATP and is required by many enzymes (Volpe, 2013).

Clinical relevance

Mineral biochemistry explains why deficiency of iron causes anaemia, of iodine causes goitre and impaired development, and of zinc impairs growth and immunity, and why disordered handling of copper or iron underlies inherited overload and deficiency syndromes (Hentze, 2010). This entry is for reference and education and does not provide dosing or treatment guidance.

Epidemiology

Iron, iodine, and zinc deficiencies are among the most widespread micronutrient problems globally, with major effects on anaemia, child development, and immunity; the population distribution of these deficiencies is addressed in the deficiency-and-toxicity topic.

Evidence & guidelines

Reference intakes and tolerable upper limits for minerals and trace elements are defined within the Dietary Reference Intake framework (IOM, 2001), and integrated biochemical accounts are found in standard textbooks (Ross et al., 2014).

History

The essentiality of minerals was established progressively: iron's role in blood was recognized in the nineteenth century, iodine's link to goitre and thyroid function drove early public-health salt iodization, and the trace elements zinc, selenium, and others were shown to be essential through deficiency studies in the twentieth century, culminating in the modern understanding of metalloproteins and regulated trace-element homeostasis.

Debates

How should body iron status be assessed and its balance managed at the population level?

Because iron is regulated at absorption and is potentially harmful in excess, the best biomarkers of iron status and the balance between preventing deficiency and avoiding overload remain active questions in nutrition science.

Seminal works

• hentze-2010-mtm
• volpe-2013
• iom-minerals-2001

Frequently asked questions

What is the difference between a macromineral and a trace element?

Macrominerals such as calcium, magnesium, and phosphorus are required in larger amounts and often serve structural and electrolyte roles, whereas trace elements such as iron, zinc, copper, and selenium are needed in much smaller quantities and act mainly as cofactors within metalloproteins.

Why is iron balance regulated at absorption rather than by excretion?

The body lacks a regulated pathway to excrete iron, so whole-body iron content is controlled chiefly by adjusting intestinal absorption and iron release from stores through the hepcidin-ferroportin system.