Minerals: Absorption and Interactions

Minerals in the body are found in large amounts, known as major minerals, or smaller amounts, known as trace minerals, needed only in small amounts, which by know means reflects their importance. Minerals are inorganic elements which always retain their chemical identity. They enter the body intact and leave the body the same way. They are not destroyed by heat, air, acid or mixing. It is the absorption of minerals and interaction with substances around them that influences the way the body handles them.

Some minerals are easily absorbed into the blood stream, transported freely and then easily excreted through the kidneys, such as potassium, whilst others require a carrier to be absorbed and transported, calcium for example.

Minerals in excess can also be toxic to the body.

Bioavailability of Minerals

Some minerals miss being absorbed due to 'binders' found in certain foods. These binders easily chemically combine with minerals, preventing their absorption and eliminating them as waste. For example, phytates, found mainly in legumes and grains; and oxalates, found in spinach and rhubarb. These foods contain more minerals due to their chemical binders.

Nutrient Interactions

Minerals absorption, metabolism and excretion can be influenced by other minerals. For example, phosphorus binds magnesium in the gastrointestinal tract, so when intake of phosphorus is high, magnesium absorption is reduced. Sodium and calcium interact, when sodium levels are high and the body is excreting the excess, calcium can be eliminated also. Often when an excess of one mineral is seen, it can create a deficiency another.

Maintaining Fluid Balance

All minerals show some responsibility to maintaining the balance of fluid in the body but the minerals of greatest importance are sodium, potassium and chloride. 

Chloride ion is part of hydrochloric acid in the stomach. Excess vomiting can upset the acid-base balance.

Individual Minerals

Calcium

Calcium needs stomach acid to keep it soluble and vitamin D to help make calcium-binding protein for absorption. When more calcium is needed by the body, such as in pregnancy, the production of calcium-binding protein is increased. Phytates, oxalates and fibre in general can interfere with calcium absorption. Phosphorus absorption is decreased by calcium.

Magnesium

Calcium and phosphate can reduce absorption of magnesium. Vitamins that increase metabolism may also increase the need for magnesium by the body. These include the vitamin B group nutrients.

The Trace Minerals

Trace minerals are found throughout the body in miniscule amounts preforming various diverse duties that only they can perform. They are active in all the systems of the body; gastrointestinal tract, cardiovascular system, blood, central nervous system, bone and muscles. The amounts found in food is dependant on the soil in which the plant is grown and how the food is processed. Sources of trace minerals are found in a variety of foods, especially whole, unprocessed foods. Many factors in the body and the diet affect the bioavailability of trace minerals.

Interactions

Interactions are common with trace minerals and can lead to deficiency, imbalance or even toxicity. Too much manganese may exacerbate an iron deficiency. Too little iron makes the body vulnerable to lead poisoning.

Iodine and Selenium are needed for healthy thyroid function, a deficiency of either can mean a reduction in thyroid hormone production.

Iodine can interact with certain foods – namely goitrogens. These are cabbage, brussel sprout, legumes and tea.

Iron – Well absorbed heme-iron comes from meat, fish and poultry.

These products also contain a factor called MFP factor which promotes the absorption of non-heme sources of iron from foods eaten at the same time. Vitamin C captures non-heme and enhances absorption if eaten at the same time. Other factors that can aid the absorption of non-heme iron include: sugars found in wine; acids such as citric acid and lactic acid from foods; HCI - stomach acid.

The body loves iron – it is the carrier of that most important element – oxygen and so the body will treat it carefully and not want to release it. Balance is maintained mainly through the absorption from food. When iron is high, absorption is low and when iron is low, absorption is increased. Inhibiting factors include: phytates, oxalates and fibres from soy, whole grains and nuts; Calcium and phosphorus (found in milk); tannic acid in tea and coffee and EDTA in food additives.

When supplementing, iron combined with particular carriers can influence absorption by the body. Click Here for more information. Some iron combinations can also cause gastic distress such as constipation. Click Here for further reading about iron supplement.

Zinc – is an important mineral involved as a co-factor in more than 100 enzymatic processes in the body. Like iron, if zinc is needed by the body – more is absorbed (provided by the food we eat), but it is also thwarted by dietary fibres and phytates.

Zinc interacts with Iron and Copper. Zinc uses the same transporter (transferrin) needed for absorption as iron – when there is overload of iron, zinc can become low and vice versa.  An over-load of zinc can also interfere with the absorption of copper.

Medication Interactions

Some medications may interact with mineral absorption. The list is extensive so it is best to check with your doctor if your medication could interact with any mineral. This may mean taking a supplement to replete lost minerals, or supplementing at a different time to taking medications.

There are the potential adverse effects from an imbalance of minerals in the body. Seeking advice if you suspect you may have a mineral deficiency. 

Factors such as nutrition, fibres and chemicals from food, stomach acid, nutrient interactions and health of the gastro-intestinal track play an important role in how minerals are absorbed.

A deficiency of any mineral can come from a lack of consumption. Eating a balanced diet of whole, natural foods realistically should supply all the body needs, but due to a lack of minerals from the soil can mean a deficiency is possible. In Australia, iodine is one mineral that is of low level in our soils.

Evaluating mineral status can be problematic due to the fact that most minerals do not reside in the blood, simple blood test may not reveal a true picture. Measurement of urine excretion rates can provide useful information on dietary intake for those minerals that are excreted in excess by the kidneys. Hair analysis is a valuable tool. A dietary intake questionaire on food intake will often reveal which minerals may be lacking - for example, iron if you do not consume meat. Your doctor can suggest the right test for you if he suspects a mineral issue.

References

Whitney, Eleanor Noss; Cataldo, Corinne Balog; Rolfes, Sharon Rady; 2002, Understanding Normal and Clinical Nutrition 6th Edition, Wadsworth/Thompsons Learning, Australia

Henry, Osiecki; The Nutrient Bible 9th Edition, Bio Concepts, AG Publishing; QLD, Australia

https://pubchem.ncbi.nlm.nih.gov/compound/edta

Biomarkers of Trace Mineral Intake and Status https://academic.oup.com/jn/article/133/3/948S/4688068