Trace Minerals

1. What Are Trace Minerals?

Trace minerals are classified as minerals required in the diet each day in smaller amounts, specifically 100 milligrams or less. These include copper, zinc, selenium, iodine, chromium, fluoride, manganese, molybdenum, and others. Although trace minerals are needed in smaller amounts, it is important to remember that a deficiency in a trace mineral can be just as detrimental to your health as a major mineral deficiency.

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Trace Minerals

Minerals required in the diet each day in smaller amounts, specifically 100 milligrams or less.

2. Iron

Iron is a vital mineral that plays a key role in many functions of the body, particularly in the transport of oxygen in the blood. It is an essential nutrient that we must get from our diet because our body cannot produce it on its own. Iron is a crucial component of hemoglobin, the protein in red blood cells responsible for carrying oxygen from the lungs to the rest of the body. Without enough iron, your blood cannot carry sufficient oxygen, which can lead to fatigue and weakness. Iron is also part of myoglobin, a protein in muscles that helps store and transport oxygen, which ensures your muscles have the oxygen they need to function efficiently during physical activity. It is involved in several enzymatic processes, including those that help with energy production and immune system function. Iron is involved in the immune system's ability to fight infections because it helps the body produce and activate immune cells to respond to pathogens. Iron plays a role in the metabolism of neurotransmitters, which are essential for brain function and cognitive health. Iron deficiency has been linked to impaired cognitive development and memory issues, especially in infants and young children.

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Hemoglobin is composed of four peptides. Each contains a heme group with iron in the center. The iron in hemoglobin binds to oxygen in the capillaries of the lungs and transports it to cells where the oxygen is released. If iron level is low, hemoglobin is not synthesized in sufficient amounts, and the oxygen-carrying capacity of red blood cells is reduced, resulting in anemia. When iron levels are low in the diet, the small intestine more efficiently absorbs iron in an attempt to compensate for the low dietary intake, but this process cannot make up for the excessive loss of iron that occurs with chronic blood loss or low intake.

The bioavailability of iron is highly dependent on dietary sources. Heme iron is found in animal products, particularly in red meat, poultry, and fish. About 15–35% of heme iron is absorbed by your body. Non-heme iron is found in plant-based foods like beans, lentils, tofu, spinach, and fortified cereals. Non-heme iron is less efficiently absorbed by the body so that only about 2–20% of it is absorbed.

Some plants contain chemicals (such as phytate, oxalates, tannins, and polyphenols) that inhibit iron absorption. Although, eating fruits and vegetables rich in vitamin C alongside iron-containing foods increases iron absorption. People with plant-based diets are at higher risk for iron deficiency, but careful meal planning can prevent its development. Iron deficiency is the most common of all micronutrient deficiencies.

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Hemoglobin

A protein found in red blood cells that is responsible for transporting oxygen from the lungs to the rest of the body and returning carbon dioxide from the tissues back to the lungs for exhalation. It is made up of four protein subunits, each containing an iron atom that binds to oxygen.

Iron

A trace mineral that is needed for the production of other iron-containing proteins such as myoglobin.

Myoglobin

A protein found in the muscle tissues that enhances the amount of available oxygen for muscle contraction.

2a. Iron Toxicity

While iron is essential for health, iron overload can also be dangerous. The body does not have a good way of getting rid of excess iron, so it can build up over time. Excess iron can accumulate in organs like the liver, heart, and pancreas, leading to hemochromatosis, a condition that causes damage to these organs over time. Symptoms of hemochromatosis include extreme fatigue, arthritis, joint pain, and severe liver and heart toxicity. In children, death has occurred from ingesting as little as 200 mg of iron, and therefore, it is critical to keep iron supplements out of children’s reach. The tolerable upper intake level for iron in adults is 45 mg per day. Excessive intake from food is rare and supplements should be used carefully.

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Hemochromatosis

A disorder characterized by the excessive absorption of iron from the digestive tract, leading to an abnormal buildup of iron in various organs, particularly the liver, heart, and pancreas. Over time, this iron accumulation can cause serious health problems, including liver disease (such as cirrhosis), diabetes, heart disease, joint problems, and hormonal imbalances.

2b. Dietary Reference Intakes and Sources of Iron

The following charts indicate the dietary reference intakes of iron.

2c. Iron-Deficiency Anemia

Iron-deficiency anemia develops from insufficient iron levels in the body, resulting in fewer red blood cells containing lower amounts of hemoglobin. Regardless of the cause (be it from low dietary intake of iron or via excessive blood loss), iron-deficiency anemia has the following signs and symptoms, which are linked to the essential functions of iron in energy metabolism and blood health:

• Fatigue
• Weakness
• Pale skin
• Shortness of breath
• Cold hands and feet
• Headache
• Brittle nails and hair loss
• Restless leg syndrome
• Dizziness
• Swollen, sore tongue
• Abnormal heart rate

key concept

Iron-deficiency anemia is diagnosed from characteristic signs and symptoms and confirmed with simple blood tests that count red blood cells and determine hemoglobin and iron content in blood. Anemia is most often treated with iron supplements and increases the consumption of foods that are higher in iron. Iron supplements have some adverse side effects, including nausea, constipation, diarrhea, vomiting, and abdominal pain. Reducing the dose at first and then gradually increasing to the full dose often minimizes the side effects of iron supplements.

Avoiding foods and beverages high in phytates, and also tea (which contains tannic acid and polyphenols, both of which impair iron absorption), is important for people who have iron-deficiency anemia. Eating a dietary source of vitamin C at the same time as iron-containing foods improves absorption of non-heme iron.

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Iron-Deficiency Anemia

A condition that develops from having insufficient iron levels in the body resulting in fewer and smaller red blood cells containing lower amounts of hemoglobin.

2d. Iron Deficiency: A Worldwide Nutritional Health Problem

The Centers for Disease Control and Prevention reports that iron deficiency is the most common nutritional deficiency worldwide. The main causes of iron deficiency worldwide are parasitic worm infections in the gut causing excessive blood loss, and malaria, a parasitic disease causing the destruction of red blood cells. In the developed world, iron deficiency is more the result of dietary insufficiency and/or excessive blood loss.

IN CONTEXT

At-Risk Populations, including infants, children, adolescents, and women, are the populations most at risk worldwide for iron-deficiency anemia by all causes. Infants, children, and even teens require more iron because iron is essential for growth. In these populations, iron deficiency (and eventually iron-deficiency anemia) can also cause the following signs and symptoms: poor growth, failure to thrive, and poor performance in school, as well as mental, motor, and behavioral disorders. Women who experience heavy menstrual bleeding or who are pregnant require more iron in the diet. One more high-risk group is the elderly. Both elderly men and women have a high incidence of anemia, and the most common causes are dietary iron deficiency and chronic disease, such as ulcer, inflammatory diseases, and cancer. Additionally, those who have recently suffered from traumatic blood loss, frequently donate blood, or take excessive antacids for heartburn need more iron in the diet.

2e. Preventing Iron-Deficiency Anemia

In young children, iron-deficiency anemia can cause significant motor, mental, and behavioral abnormalities that are long-lasting.

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In the United States, the high incidence of iron-deficiency anemia in infants and children was a major public-health problem prior to the early 1970s, but now the incidence has been reduced. This achievement was accomplished by implementing the screening of infants for iron-deficiency anemia in the health sector as a common practice, advocating the fortification of infant formulas and cereals with iron, and distributing them in supplemental food programs, such as that within Women, Infants, and Children (WIC). Breastfeeding, iron supplementation, and delaying the introduction of cow’s milk for at least the first twelve months of life were also encouraged. These practices were implemented across the socioeconomic spectrum, and by the 1980s, iron-deficiency anemia in infants had significantly declined. Other solutions had to be introduced in young children, who no longer were fed breast milk or fortified formulas and consumed cow’s milk. The following solutions were introduced to parents: provide a diet rich in sources of iron and vitamin C, limit cow’s milk consumption to less than twenty-four ounces per day, and a multivitamin containing iron.

3. Copper

Dietary copper is an essential trace mineral that plays a crucial role in several important bodily functions. Although required in very small amounts, copper is vital for overall health, and a deficiency can lead to various health issues.

Copper, like iron, assists in electron transfer in the electron-transport chain and is needed for production of ATP. It helps in the absorption, storage, and release of iron which is crucial to preventing anemia and is part of an antioxidant enzyme to help protect cells from free radical damage. Copper is involved in the synthesis of collagen and elastin, which are key structural components of connective tissue, skin, bones, and blood vessels. Copper helps form myelin and contributes to bone strength and density.

Copper deficiency is rare and can occur in individuals with limited dietary intake or certain health and genetic problems. Symptoms of deficiency may include anemia, fatigue or weakness, tingling or numbness in arms and legs, or poor immune function.

Though copper is essential, toxicity may occur and is often due to high dose supplements or genetic conditions, like Wilson’s disease. Copper toxicity may lead to nausea and vomiting, liver damage, tremors, or mood swings.

Copper is found in a variety of foods, and it is important to eat a balanced diet to meet the recommended intake. Shellfish, organ meat, nuts and seeds, whole grain, fruits, and leafy greens are all good sources of dietary copper. Copper is essential for many critical functions in the body, from producing energy and forming connective tissue to maintaining brain and immune health. It’s found in a variety of foods, and most people can meet their copper needs through a balanced diet.

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Copper

An antioxidant that assists in electron transfer in the electron-transport chain. It is a cofactor of enzymes essential for iron absorption and transport.

4. Zinc

Zinc is another essential trace mineral that plays a crucial role in many biological functions in the body. Like copper, it is needed in small amounts but is vital for immune health, wound healing, and cell division. Because of the role zinc plays in DNA production and cell division, it is especially important during periods of rapid growth, like childhood, adolescence, and pregnancy. Zinc is necessary for the proper functioning of taste and smell receptors.

In adults, severe zinc deficiency can cause hair loss, diarrhea, skin sores, loss of appetite, and weight loss. Zinc is a required cofactor for an enzyme that synthesizes the heme portion of hemoglobin and severely deficient zinc diets can result in anemia. Zinc deficiency can cause delayed growth in children.

Zinc can be found in both animal and plant-based foods, though it is typically absorbed more easily from animal sources. Cereal grains and some vegetables contain chemicals, one being phytate, which blocks the absorption of zinc and other minerals in the gut. High bioavailability foods include oysters, red meat, poultry, seafood, and dairy. Plant sources are less bioavailable due to phytates, but some sources are legumes, nuts and seeds, whole grains, and vegetables like spinach and mushrooms.

The tolerable upper intake level (UL) for zinc for adults is 40 mg per day, meaning this is the highest amount considered safe to consume daily without adverse effects. The recommended daily intake of zinc varies by age and gender:

• Infants (0–6 months): 2 mg
• Children (1–3 years): 2.5 mg
• Children (4–8 years): 5 mg
• Boys (9–13 years): 8 mg
• Girls (9–13 years): 8 mg
• Men (14 years and older): 11 mg
• Women (14 years and older): 8 mg
• Pregnant women: 11 mg
• Lactating women: 12 mg

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It is estimated that half of the world’s population has a zinc-deficient diet. This is a consequence of the lack of red meat and seafood in the diet and reliance on cereal grains as the main dietary staple.

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Zinc

A cofactor for over two hundred enzymes in the human body and plays a direct role in RNA, DNA, and protein synthesis.

5. Iodine

Iodine is an essential trace mineral that plays a critical role in maintaining healthy thyroid function, which regulates metabolism and growth. Since iodine is not naturally produced by the body, it must be obtained through diet or supplements. Iodine is a key component of thyroid hormones (thyroxine, T4, and triiodothyronine, T3). These hormones regulate the body's metabolism, energy production, and growth. Iodine deficiency is a global health issue, although it is less common in developed countries due to iodine fortification programs, even minor deficiencies can impair a baby’s brain development.

Iodine deficiency can lead to goiter (an enlarged thyroid gland due to the body's attempt to capture more iodine from the bloodstream), hypothyroidism (low levels of thyroid hormones), cognitive impairment (in children, iodine deficiency can cause developmental delays, learning difficulties, and intellectual disabilities), and deficiency during pregnancy can lead to stunted fetal growth, cretinism, or even stillbirth.

The recommended dietary intake of iodine varies by age, gender, and life stage:

• Infants (0–6 months): 110 micrograms (mcg)
• Children (1–3 years): 90 mcg
• Children (4–8 years): 90 mcg
• Children (9–13 years): 120 mcg
• Adults (14 years and older): 150 mcg
• Pregnant women: 220 mcg
• Lactating women: 290 mcg

key concept

The development of goiter may often be the most visible sign of chronic iodine deficiency, but the consequences of low levels of thyroid hormone can be severe during infancy, childhood, and adolescence, as it affects all stages of growth and development. Thyroid hormone plays a major role in brain development and growth, and fetuses and infants with severe iodine deficiency develop a condition known as cretinism, in which physical and neurological impairment can be severe. The World Health Organization (WHO) estimates iodine deficiency affects over two billion people worldwide, and it is the number one cause of preventable brain damage worldwide.

Some of the best sources of iodine are from seaweed, dairy products, eggs, fish and shellfish, and iodized salt.

Dietary iodine is essential for proper thyroid function, metabolic regulation, and developmental health. It is primarily found in seafood, dairy, eggs, and iodized salt. While iodine deficiency can lead to serious health issues, such as goiter and developmental delays, iodine toxicity can also occur if too much is consumed, particularly through supplements. It is important to get enough iodine but not to exceed the recommended levels.

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Iodine

A trace mineral that is essential for the synthesis of thyroid hormone, which regulates basal metabolism, growth, and development.

Goiter

An abnormal enlargement of the thyroid gland, which is located at the base of the neck. The thyroid gland produces hormones that regulate metabolism, and when it becomes enlarged, it can be a sign of an underlying issue, such as iodine deficiency, autoimmune diseases, like Hashimoto's thyroiditis or Graves' disease, or other thyroid disorders.

Hypothyroidism

A condition in which the thyroid gland produces insufficient amounts of thyroid hormones, which are essential for regulating metabolism, energy production, and overall body functions. This hormone deficiency can slow down many of the body’s processes.

REFERENCES

Fact Sheet for Health Professionals: Zinc. National Institute of Health, Office of Dietary Supplements. ods.od.nih.gov/factsheets/Zinc-HealthProfessional/. Updated February 11, 2016. Accessed November 10, 2017.

Health Professional Fact Sheet: Iodine. National Institute of Health, Office of Dietary Supplements. ods.od.nih.gov/factsheets/Iodine-HealthProfessional/. Updated June 24, 2011. Accessed November 10, 2017.