Zinc: Benefits, Dosage, Natural Sources, Deficiency, and excess risks
Supplementation of Zinc
Zinc & Immune System
The primary function of the immune system is surveillance over mutated, damaged, and old cells that can lead to the development of cancer and autoimmune diseases. Humans can help the body fight the disease by activating the immune system through a variety of widely available dietary supplements. Among minerals, these will unquestionably include zinc, which performs catalytic, structural, and regulatory functions in the body, making it indispensable for the proper functioning of the body.
The immune system is particularly sensitive to changes in the level of zinc; in fact, it seems that every response is in some way directly or indirectly related to zinc.
The human body cannot store zinc reserves, and a deficiency can arise relatively quickly, e.g., through an improper diet. Zinc deficiency is a global health problem, affecting over two billion people worldwide. In more than 10% of the population, intake of zinc with meals is less than half the recommended dose, and chronic zinc deficiencies significantly increase the risk of cancer. Many patients with cancer, especially of the lungs, breast, head, and neck, have a decreased level of zinc in the blood.
Zinc & Human Intestinal Microbiome
Zinc can strongly influence the gastrointestinal microbiome due to its powerful effect on various mechanisms of the immune system and thus on the immune response, and also by affecting the permeability of the epithelium against the attacking pathogens and microorganisms or reducing mucosal inflammation of the gastrointestinal mucosa.
Zinc is an inexpensive and affordable strategy to overcome diarrhea.
However, it is worth emphasizing that each person has a entirely unique microbiome that reacts differently to both internal and external factors. Excessive zinc supplementation can adversely affect the microbiome structure and increase the risk of infection, e.g., with Clostridium difficile.
Zinc & DNA
Zinc performs very important functions in the cell by stabilizing zinc finger structures, playing an important role in the regulation of DNA replication and repair, transcription and translation, cell proliferation and maturation, and apoptosis.
Genome integrity disorders, inefficient enzymatic DNA repair mechanisms, and the loss of mechanisms controlling DNA function associated with zinc deficiency may lead to an increased risk of cancer initiation and progression.
Zinc & Apoptosis
Supplementation to correct zinc deficiencies has been shown to prevent apoptosis induced by various factors, whereas a decreased level of zinc ions may intensify cell death in the apoptosis mechanism.
Zinc generally contributes to the regulation of this main mechanism of cell death in the body and ensures the removal and destruction of mutant or damaged forms. Deregulation of this process occurs in the pathogenesis of many diseases, including cancer.
A deficiency of zinc, a strong antioxidant, undoubtedly considerably weakens the cell, making it susceptible to free radicals released from the mitochondria.
It should be stressed that properly regulated apoptosis also maintains the balance in the immune system.
Zinc & Psyche
Symptoms not directly related to oncological disease but often accompanying it include increased feelings of sadness and anxiety, low mood, a loss of interest in pleasures, reduced appetite, changes in body weight and sleep patterns, concentration disorders, and reduced cognitive abilities.
Zinc is important in the functioning of not only the immune system but also the central nervous system. It is a significant element of antioxidant mechanisms that condition the integrity of the blood-brain barrier and protect against the harmful effects of oxidative stress.
A lack of zinc in the blood is often linked to affective disorders, especially depression.
Zinc & Wound Healing
Zinc oxide is a popular over-the-counter skin treatment. It can defend against sunburns by reflecting and scattering ultraviolet rays, so they do not penetrate the skin.
It is also used to treat inflamed skin conditions like burns, eczema, bedsores, and diaper rash. The compound forms a protective barrier on the skin’s surface, repelling away moisture and allowing the skin to heal.
It may also aid enzymes to break down damaged collagen tissue so that new tissue can be formed. No negative side effects have been reported.
chronic zinc deficiency is rare and is seen most commonly in people who do not absorb zinc well due to digestive disorders such as inflammatory bowel diseases or who have undergone gastrointestinal surgery.
Those with chronic liver or kidney disease are also at risk. Excessive or prolonged diarrhea can lead to a zinc deficiency, as well as severe conditions with increased zinc needs like burns and sepsis (an infection caused by harmful bacteria entering the blood). Zinc is more efficiently absorbed when taken in smaller doses and in people who are deficient in the mineral.
Vegetarians/vegans: Zinc intake is limited to plant foods like whole grains that have lower bioavailability than from animal foods.
Decreased absorption and increased loss of zinc through the urine.
Pregnant women: Increased zinc needs for the fetus and during lactation.
Alcohol: Long-term alcohol consumption is associated with impaired zinc absorption and increased
urinary zinc excretion.
Signs of Deficiency
Loss of taste or smell
Delayed wound healing
Toxicity occurs almost exclusively from zinc supplements rather than food. There have been no reports of consuming too much zinc from the diet alone.
Signs of toxicity
Abdominal pain or cramping,
Recommended Dietary Allowance (RDA)
Natural Sources of Zinc
Meats, poultry, and seafood are rich in zinc. Some plant foods like legumes and whole grains are also good sources of zinc, but they also contain phytates that can bind to the mineral, lowering its absorption.
Supplements contain several forms of zinc, including zinc gluconate, zinc sulfate, and zinc acetate. Research has not determined whether differences exist among forms of zinc in absorption, bioavailability, or tolerability.
It is important not to take supplemental zinc unless it is known that the diet is low in foods containing zinc or a zinc deficiency is confirmed.
Research has shown that zinc supplementation (5 mg/kg) for four weeks significantly increased the number of NK cells (Natural killer cells). NK cells play a key role not only in the direct killing of target cells, but also in sending signals that stimulate an immune response. Thus, NK cells are involved in processes preventing cancer, and zinc is necessary fortheir activation.
Gastrointestinal distress has been reported at doses of 50 to 150 mg/day of supplemental zinc.
Zinc supplementation in the amount of 20 mg/day zinc for five weeks in children with zinc deficiency was found to increase the percentage of CD4+ and CD8+ cells, and in older individuals, 48-day supplementation led to an increase in Th lymphocytes (The T helper cells (Th cells), also known as CD4+ cells, are a type of T cell that play an important role in the immune system, particularly in the adaptive immune system. They help the activity of other immune cells by releasing T cell cytokines. These cells help suppress or regulate immune responses).
A LOAEL (The lowest-observed-adverse-effect level) of 60 mg/day was calculated by adding the supplemental intake of 50 mg/day with the rounded estimate of dietary intake, 10 mg/day. Support for a LOAEL of 60 mg/day is provided by other studies showing altered copper balance after zinc supplementation.
Zinc is an essential trace element for the activation or structural stabilization of a great number of enzymes and transcription factors as well as the immune and antioxidant response, apoptosis, and mental health.
Supplementation and an optimal intake of zinc restore the normal immune response and reduce the risk of infection.
However, the optimal immunostimulatory dose of zinc has not been determined. At the same time, it has been demonstrated that an excess amount of zinc can be dangerous due to its immunosuppressive effect.
Knowledge of the dual effect of zinc is needed to evaluate its beneficial and negative effects on the prevention and treatment of cancer.
Role of Zinc in Immune System and Anti-Cancer Defense Mechanisms (Dorota Skrajnowska and Barbara Bobrowska-Korczak)
US National Library of Medicine, National Institutes of Health
Dietary Reference Intakes: The Essential Guide to Nutrient Requireme (Jennifer J. Otten, Jennifer Pitzi Hellwig, Linda D. Meyers)