Understanding Minerals: Major vs Trace, Elemental Amounts, Absorption and Excess

Overview

Minerals are nutrients found in food, drink and supplements. The body uses them for many jobs, including keeping bones, muscles, the heart and the brain working, and for making enzymes and hormones. [1] Most people get the minerals they need from a wide variety of foods. [1] Some people with certain health problems or medicines need to get less of a mineral, not more. [1] This page is the starting point for the Minerals section. It explains how to read mineral facts without being misled. It is information only and is not personal medical advice.

Evidence labels used in this section: established nutritional role, evidence in adequately nourished people, promising but limited, mixed, insufficient evidence, marketing claim, and Proper evidence not found (used when we searched and found nothing usable).

Major and trace minerals

MedlinePlus (US National Library of Medicine) describes two groups. The body needs larger amounts of the macrominerals: calcium, phosphorus, magnesium, sodium, potassium, chloride and sulfur. [1] It needs only small amounts of the trace minerals, which include iron, manganese, copper, iodine, zinc, cobalt, fluoride and selenium. [1] "Trace" describes how much the body needs, not how important the mineral is, and it does not mean a trace mineral needs a supplement.

• Larger-amount minerals: calcium, magnesium, potassium, sodium and chloride and phosphorus.
• Trace minerals: iron, zinc, copper, manganese, iodine, selenium, chromium, molybdenum and fluoride.
• Fluids and salts: electrolytes and electrolyte supplements.

The Minerals hub lists every guide in this section.

Elemental amounts: what the label number means

Many mineral supplements are a mineral attached to another substance, for example magnesium oxide or magnesium citrate. The US FDA states that the Supplement Facts label declares the amount of elemental magnesium in a serving, [2] not the amount in the entire magnesium-containing compound. [2] One published study listed a tablet with 248.72 mg of magnesium oxide, containing 60% magnesium, which corresponds to 149 mg of magnesium. [3] So a compound weight and an elemental amount can differ a lot. Compare elemental amounts with reference values, and keep mg and mcg apart: 1,000 micrograms equal 1 milligram. [4] Differences between forms are covered in Magnesium forms compared and Calcium carbonate vs citrate.

Too little and too much

Both can cause problems, and the picture differs by mineral.

• Low levels often have causes other than diet. For magnesium, MedlinePlus lists medicines such as diuretics and proton pump inhibitors. [10] Symptoms such as fatigue, weakness and muscle cramps can be caused by many conditions, so they do not show a deficiency on their own. [11]
• High levels from food alone are uncommon. MedlinePlus says it is rare to get too much magnesium from food alone. [11] For potassium, poor kidney function can stop the body removing enough potassium, and extra potassium from salt substitutes or supplements can add to it. [12] Either can raise blood levels.
• Child poisoning. The NHS warns that very high doses of iron can be fatal, particularly if taken by children. [13] If a child may have swallowed iron or any supplement, call Poison Help at 1-800-222-1222 (US) or 911 in an emergency; see Iron overdose and child safety.
• Thyroid. The NHS says high doses of iodine over long periods could change the way the thyroid gland works. [14]

Testing and when to ask for help

Blood tests have limits. One research paper notes that serum magnesium values reflect only 1% of the body's magnesium content. [3] Do not diagnose yourself from symptoms; see Deficiency testing and its limits.

Talk to a clinician or pharmacist before using mineral supplements if you have kidney disease, take regular medicines, are pregnant or breastfeeding, are older, or are giving minerals to a child. Supplements can interact with medicines or carry risks before surgery. [19] Useful next reads: Minerals, supplements and kidney disease, How interactions work, Reading supplement labels and Quality testing and certifications.