From A to Zinc

 An Overview of A Mineral Essential to Health

After iron, zinc is the most abundant element in the human body, with approximately 2 to 4 g distributed among the muscles (60%), bones (20%), liver, and skin. Given its abundance, concerns about zinc deficiency is often overlooked; however, as discussed in this article, certain populations and individuals may benefit from supplementation. Caution is advised, though, as too much zinc does come with its own risks, which will be discussed below. The risks of deficiency have been extensively studied, and research into who can benefit from dietary changes or supplementation is constantly bringing more clarity into the matter.

Zinc deficiency among the general population is more prevalent in endemic areas of malnourishment. Among the elderly, however, zinc deficiency is considered more common irrespective of location, possibly affecting as much as 30% of the elderly population. Dietary zinc comes from relatively varied sources, both vegetable (seaweed, whole grains, mushrooms, watercress, sunflower and pumpkin seeds, lentils, millet, quinoa, tofu, brewer’s yeast, etc.) and animal (oysters, poultry, egg, fatty fish, and shellfish). Its bioavailability is higher in animal products, and the recommended daily allowance is approximately 10 mg/d for adults and 12 mg/d for pregnant or lactating women. Zinc’s current popularity is because it is an essential mineral that helps strengthen the immune system, especially at the onset of infection. However, this mineral is much more than just an immune support…

A Versatile Mineral ^1,2,3

Zinc is essential for gene expression, cell multiplication, cell energy production, and many biochemical reactions in the body, including protein synthesis. Zinc is needed for tissue formation and cell-membrane stability. Like magnesium, zinc is involved as a cofactor in several hundred enzymatic reactions. By helping increase the number of T lymphocytes during infection, this mineral is a pillar in the maintenance of the immune system.⁴ Zinc also inhibits the development of certain viruses such as influenza or herpes simplex. Zinc has a major antioxidant role; it contributes to the proper enzymatic functioning of superoxide dismutase (SOD), which captures superoxide and prevents oxidative stress as well as age-related degenerative disorders. In the skin and connective tissue, and in conjunction with lysyl oxidase, zinc is involved in the synthesis of elastin and collagen; it also acts with tyrosinase in the production of melanin in the dermis. Its anti-inflammatory and healing properties make it a great choice for dermatological disorders such as acne. By promoting the synthesis of cystine and methionine, zinc supports keratin, an important component of hair. Zinc is crucial at the hormonal level: It is essential in testosterone and insulin synthesis, is involved in the biosynthesis of prostaglandins from polyunsaturated fatty acids and is a cofactor for delta‑6-desaturase, an important enzyme in the metabolism of both omega‑3 and omega‑6. Zinc also contributes to prostate health and sperm quality.

Symptoms of Deficiency

Zinc deficiency is characterized by a weakened immune system, loss of appetite, stunted growth, and fatigue. A more pronounced deficiency causes symptoms such as:

• Skin disorders (eczema, psoriasis, alopecia, white spots on the nails, stretch marks)
• Pancreatic disorders / diabetes
• Dysmenorrhea
• Prostate hypertrophy
• Infertility
• Ageusia (absence of taste perception)
• Changes in smell and taste
• Hair loss
• Delayed wound healing
• Eye lesions or macular degeneration

The main causes of zinc deficiency are:

• Strict vegetarian or vegan diet, with a high intake of foods rich in phytates and lignin
• Age
• Bowel disorders (Crohn’s disease, celiac disease, malabsorption)
• Pregnancy
• Renal failure
• Chronic diarrhea
• Alcoholism
• Anorexia or other eating disorders

Selected Excerpts from the Scientific Literature on the Benefits of Zinc Supplementation

Covering all of zinc’s benefits would fill a book, as knowledge and research on the subject is ubiquitous and significative. We have chosen to focus on two of the main benefits of zinc.

Immune and Anti-infective Support

In a review of 20 clinical studies of healthy adults, the authors concluded that zinc supplementation can reduce the duration of flu symptoms by an average of 2.25 days (95% CI: −3.39 to −1.12). They further determined that zinc supplementation helps reduce flu episodes by 53% in children under 10 years (RR: 0.64, 95% CI: 0.47 to 0.88).⁵ Zinc deficiency is associated with a weakened immune system, which opens the door to infections, for example by the human papillomavirus (HPV), which produces warts. Oral or local treatments with zinc have shown its effectiveness against warts; in fact, according to two randomized, placebo-controlled trials, high-dose oral administration of zinc sulphate (10 mg/kg/d) resolved the warts in two months in 84 to 87% of patients experiencing recurrent warts.⁶

The authors of a literature review aiming to assess zinc’s potential in the treatment of SARS‑CoV‑2 infection (COVID‑19) believe that the administration of zinc is beneficial for most of the population, in particular for people whose zinc status is not optimal, particularly the elderly. They concluded that, despite the lack of results from clinical studies with COVID‑19 patients (of which four are still in progress ^7,8,9,10), zinc may be an adjuvant to current treatment protocols, because “zinc supplementation improves the mucociliary clearance, strengthens the integrity of the epithelium, decreases viral replication, preserves antiviral immunity, attenuates the risk of hyper-inflammation, supports anti-oxidative effects and thus reduces lung damage and minimized secondary infections.” ¹¹ At 30–50 mg/d, zinc is on the list of nutraceuticals that have the potential to stimulate type 1 interferon response to RNA viruses, including influenza viruses and SARS‑CoV‑2.^12,13 Other such nutraceuticals include N‑acetylcysteine, alpha‑lipoic acid, beta‑glucans, spirulina, and elderberry.

Thyroid and Cardiometabolic Support

Zinc plays a role in the synthesis of thyroid hormones and in the conversion of thyroxine (T4) into triiodothyronine (T3). Zinc deficiency can therefore impact this gland as well as its metabolic regulatory functions. In a randomized, double-blind, controlled study, researchers evaluated the effects of zinc and selenium supplementation in 68 overweight and obese women with hypothyroidism. Serum T3 levels and mean T3:T4 ratio (p < 0.05) were favourably increased. The researchers concluded that zinc (alone or in combination with selenium) improved thyroid gland function.¹⁴

Zinc deficiency is often observed in people with diabetes, as a lack of zinc disrupts insulin production.^15,16 Hyperglycemia further increases the tendency towards zinc deficiency, by increasing the urinary excretion of zinc. Zinc supplementation in people with diabetes or prediabetes has reduced the impact of oxidative stress associated with chronic hyperglycemia,¹⁷ and improved glucose metabolism and insulin sensitivity.^18,19,20 These effects may have a positive impact on overall cardiovascular health and may reduce the risk of long-term cardiovascular disease. In a systematic literature review, the authors report that “[t]he effect of zinc appears to be more pronounced in vulnerable populations, such as those with existing Type 2 DM or established risk factors of diseases.” ²¹

Careful Use of Zinc

While most studies show zinc’s beneficial effects for various health conditions, particularly in people with zinc deficiency, many authors and practitioners also warn about misuse of this mineral. The main reason is that excess zinc intake over several months may lead to decreased copper levels, which is also involved in many physiological functions (immune and nervous system, antioxidant, and anti-inflammatory, cardiometabolic function, and osteoarticular integrity, to name a few).^2,3 It is therefore highly recommended to test zinc levels before starting supplementation, to assess whether the body is deficient or nearly so. Healthy people are advised to take zinc for short periods of time only, to prevent copper deficiency–related symptoms. These include increased levels of advanced glycation end‑products (AGEs), joint pain, neurological disorders, or bone metabolism and glucose disorders. If you are uncertain whether you should be supplementing with zinc and if it may benefit you, the support of a naturopathic health-care practitioner, who has received training on the subject, is recommended.