Minerals

Zinc

Zinc

Zinc is an essential micronutrient that is critical for a wide array of life functions, including growth, immune resistance, and metabolic regulation. Since zinc cannot be stored in significant amounts in the body, a regular dietary intake is necessary.

Zinc exists in the body in various states:

  • Dietary Micronutrient: Obtained from the diet.
  • Circulating Form: Approximately 70% of zinc in the bloodstream is bound to albumin.
  • Intracellular Form: It is present as intracellular free zinc in immune cells, where it participates in signaling events.

Zinc is found in a wide variety of foods, though the amount and absorbability vary significantly.

The richest sources of zinc include oysters, meat (beef, lamb, pork, chicken), and other shellfish (crab, lobster). Good sources are also found in dairy foods, nuts (cashews, peanuts), seeds (hemp, pumpkin), legumes (beans, lentils), whole grains, and fortified breakfast cereals.

Zinc from animal sources is generally better absorbed than zinc from plant sources. Dietary phytates in legumes and grains reduce zinc bioavailability, acting as inhibitors of absorption.

Zinc determines a greater number of critical life functions than any other single micronutrient. Its primary roles include:

1. Enzyme and Gene Regulation

 Zinc is a required cofactor for the activity of over 300 enzymes and is necessary for the function of over 1000 transcription factors.

2. Immune System

It is a second messenger of immune cells. It is crucial for cell-mediated immune function and resistance to infections.

3. Metabolism

It plays a vital role in the regulation of glucose metabolism.

Daily intake recommendations vary substantially by age. In children the recommended dose varies from 4.6 to 7.4 mg/day.

Deficiency

Symptomatic deficiency is a significant global health issue. Clinical signs include growth retardation, cell-mediated immune dysfunction, and cognitive impairment. 

Overdose

Excessive zinc intake can inhibit the absorption of copper and iron. This can result in subsequent copper deficiency and anemia.

  • zinc acetate
  • zinc L-ascorbate
  • zinc L-aspartate
  • zinc bisglycinate
  • zinc chloride
  • zinc citrate
  • zinc gluconate
  • zinc lactate
  • zinc L-lysinate
  • zinc malate
  • zinc mono-L-methionine sulphate
  • zinc oxide
  • zinc carbonate
  • zinc L-pidolate
  • zinc picolinate
  • zinc sulphate

Lowe, N. M., Hall, A. G., Broadley, M. R., Foley, J., Boy, E., & Bhutta, Z. A. (2024). Preventing and controlling zinc deficiency across the life course: A call to action. Advances in Nutrition, 15(3), 100181. 

Stiles, L. I., Ferrao, K., & Mehta, K. J. (2024). Role of zinc in health and disease. Clinical and Experimental Medicine, 24(1), 38.

Prasad, A. S. (2013). Discovery of human zinc deficiency: Its impact on human health and disease. Advances in Nutrition, 4(2), 176–190.

Selenium

Selenium

Selenium (Se) is an essential trace element (micronutrient) that the human body requires for proper function but cannot produce on its own, meaning it must be obtained through diet. It is a fundamental component of various enzymes and proteins, collectively known as selenoproteins.

Selenium is found in both animal and plant sources. 

  • Animal sources: meats like kidney and liver or seafood.
  • Plant sources: The amount of selenium in plant foods is highly dependent on the selenium content of the soil they are grown in.The richest sources include brazil nuts, onions, broccoli and seeds.

Selenium's primary roles in the body are carried out by the selenoproteins, which are crucial for:

1. Antioxidant Defense

Many selenoproteins, such as glutathione peroxidases, act as powerful antioxidants, helping to protect cells from damage caused by free radicals and oxidative stress.

2. Thyroid Function

Selenoproteins are necessary for the metabolism and regulation of thyroid hormones, which are vital for growth and metabolism.

3. Immune System

Selenium supports the proper function of the immune system and is involved in modulating immune responses.

4. DNA Synthesis

It is involved in DNA production and protection against cell damage.

Daily intake recommendations vary substantially by age. In children the recommended dose varies from 20 to 55 µg/day.

Deficiency

Selenium deficiency is rare in generally healthy populations. It is more common in individuals with severe gastrointestinal conditions. Severe deficiency can lead to impaired immune function and muscle weakness.

Overdose

Consuming too much selenium can lead to toxicity, known as selenosis. The common symptoms of selenosis may include nausea, vomiting, fatigue and irritability.

  • L-selenomethionine
  • selenium enriched yeast
  • selenious acid
  • sodium selenate
  • sodium hydrogen selenite
  • sodium selenite

Genchi, G., Lauria, G., Catalano, A., Sinicropi, M. S., & Carocci, A. (2023). Biological Activity of Selenium and Its Impact on Human Health. International Journal of Molecular Sciences, 24(3), 2633.

Sousa, J. A., McKay, D. M., & Raman, M. (2024). Selenium, Immunity, and Inflammatory Bowel Disease. Nutrients, 16(21), 3620. 

Avery, J. C., & Hoffmann, P. R. (2018). Selenium, Selenoproteins, and Immunity. Nutrients, 10(9), 1203.

Iodine

Iodine

Iodine is an essential mineral nutrient vital for various physiological functions in the body. It is required for the synthesis of thyroid hormones, which are crucial throughout the lifespan, especially for brain development. A healthy gut absorbs around 90 % of the iodide intake.

The iodine content of food is highly variable, largely depending on the iodine content of the soil, water, and animal feed. 

  • Animal sources: dairy products, eggs and seafood
  • Plant sources: seaweeds (richest sources), bread and iodized salt

Iodine's primary function is as an integral component of the thyroid hormones: thyroxine (T4) and triiodothyronine (T3). These hormones, produced by the thyroid gland, are essential for:

1. Metabolism

 Thyroid hormones regulate the basal metabolism and thermogenesis influencing energy levels and weight. 

2. Brain development

Both T4 and T3 critically influence brain development and function in children and adults.

3. Immune system

Thyroid hormones can directly affect multiple branches of the immune system cells by enhancing dendritic cell antitumor immunity, B cell differentiation, phagocytosis, natural killer cytotoxicity, inducing higher expression of cytokines, and increasing the frequency of T cell memory cells.

For children the EFSA recommended dose is between 90 -120 µg per day.

Deficiency

Inadequate iodine intake is a significant global public health concern, with consequences collectively known as Iodine Deficiency Disorders (IDDs). IDDs are the most common cause of preventable mental retardation and brain damage worldwide.

Overdose

Excessive iodine intake can disrupt thyroid function, although this is less common than deficiency. Excessive iodine intake may lead to hyperthyroidism, autoimmune thyroid disease. The thyroid gland has a protective mechanism, known as the Wolff-Chaikoff effect, to temporarily halt hormone production in response to high iodine levels.

  • sodium iodide
  • sodium iodate
  • potassium iodide
  • potassium iodate

Hatch-McChesney, A., & Lieberman, H. R. (2022). Iodine and iodine deficiency: A comprehensive review of a re-emerging issue. Nutrients, 14(17), 3474.

Lisco, G., De Tullio, A., Triggiani, D., Zupo, R., Giagulli, V. A., De Pergola, G., Piazzolla, G., Guastamacchia, E., Sabbà, C., & Triggiani, V. (2023). Iodine deficiency and iodine prophylaxis: An overview and update. Nutrients, 15(4), 1004.

De Vito, P., Incerpi, S., Pedersen, J. Z., Luly, P., Davis, F. B., & Davis, P. J. (2011). Thyroid hormones as modulators of immune activities at the cellular level. Thyroid, 21(8), 879–890.