Zinc’s Many Roles in the Human Body

Zinc plays a crucial role in the functioning of over 80 enzymes, and the adult body typically contains around 2-3 grams of this essential mineral. Found in every part of the body, the majority of zinc is stored in muscles and bones (about 90%). The highest concentrations are located in the middle ear, cochlea, eyes, brain, prostate, and sperm.

Zinc and Brain Function

High levels of zinc are present in the brain (particularly the hippocampus), leading many medical researchers to suspect that zinc acts as a neurotransmitter. A deficiency in zinc can lead to irritability, anger episodes, weakened immune function, acne, stunted growth, reduced taste and smell sensitivity, and impaired wound healing. Research shows a significant prevalence of zinc deficiency among individuals diagnosed with ADD, autism, depression, schizophrenia, eating disorders, and bipolar disorder (2). Low zinc levels have been linked to behavioral disorders.

A considerable percentage of individuals with behavioral disorders show abnormal levels of copper, zinc, lead, cadmium, calcium, magnesium, and manganese in their blood, urine, and tissues. This abnormality often involves a malfunction of the metal-binding protein, metallothionein, and results in depressed zinc levels in blood plasma alongside symptoms of zinc deficiency.

A study by WJ Walsh, presented at the Neuroscience Annual Meeting in 1994, highlighted an elevated serum copper and depressed plasma zinc concentration among assaultive young males compared to controls (1). Clinical observations from the Pfeiffer Treatment Center corroborated these findings, noting zinc depletion in over 4,000 behaviorally disordered patients. The research indicates that the copper/zinc ratio is more critical than individual copper or zinc levels. Zinc deficiency often elevates blood copper levels due to the competitive dynamic between these metals. Elevated blood copper has been associated with episodic violence, hyperactivity, learning disabilities, and depression. Zinc also counteracts the effects of cadmium, lead, and mercury.

Zinc’s Role in Growth and Cell Division

Zinc is vital for growth and cell division, making it especially important during pregnancy to support the rapidly dividing cells of the growing fetus. Adequate zinc levels help to prevent congenital abnormalities and pre-term deliveries. Furthermore, zinc is crucial for activating growth in height, weight, and bone development in infants, children, and teenagers.

Zinc and Fertility

Zinc plays a significant role in fertility. In males, zinc protects the prostate gland from infections such as prostatitis and from enlargement, known as prostatic hypertrophy. It also helps maintain sperm count, mobility, and normal serum testosterone levels. In females, zinc can alleviate menstrual problems and symptoms associated with premenstrual syndrome (PMS).

Zinc’s Impact on the Immune System

Zinc stands out among vitamins and minerals for its strong effect on the immune system. It plays a unique role in T-cells, with low zinc levels leading to reduced and weakened T-cells, which are less capable of recognizing and fighting infections (3). Increasing zinc levels has proven effective in combating pneumonia, diarrhea, and other infections, as well as reducing the duration and severity of the common cold.

Zinc’s Influence on Taste, Smell, and Appetite

Zinc activates areas in the brain that process information from taste and smell sensors. Plasma zinc levels and zinc's interaction with other nutrients, such as copper and manganese, influence appetite and taste preference. Zinc is also used to treat anorexia.

Zinc for Skin, Hair, and Nails

Zinc accelerates skin cell renewal and is used in creams to soothe diaper rash and heal cuts and wounds in babies. It effectively treats acne, psoriasis, and neurodermatitis (4). Zinc also acts as an anti-inflammatory agent, soothing skin affected by poison ivy, sunburn, blisters, and certain gum diseases. For hair, insufficient zinc levels can result in hair loss, thin and dull hair, and premature greying. Several shampoos contain zinc to help prevent dandruff.

Zinc and Vision

High concentrations of zinc are found in the retina, but these levels decline with age, contributing to the development of age-related macular degeneration (AMD), which can lead to partial or complete loss of vision. Zinc may also protect against night blindness and prevent cataracts (5).

Foods Rich in Zinc

Zinc is primarily obtained through diet, with major sources including oysters, which contain over 1000% in a serving, and lesser amounts in red meat, poultry, fish, seafood, whole cereals, and dairy products. Oysters offer the highest bioavailability of zinc, while plant-based foods generally have lower absorption rates due to dietary fiber and phytic acid, which inhibit zinc absorption. Vegetarians are particularly susceptible to zinc deficiency.

Top 5 Zinc-Containing Foods:

1. Oysters: Oysters are renowned for their exceptionally high zinc content, with some varieties containing up to 74 mg of zinc per 3-ounce serving.

2. Beef: Beef, especially red meat, is a great source of zinc. A 100-gram serving of cooked ground beef can provide about 12.3 mg of zinc.

3. Pumpkin Seeds: Pumpkin seeds are a plant-based source of zinc, offering around 6.6 mg per 100 grams. They're a convenient and versatile snack.

4. Lentils: Lentils and other legumes are good sources of zinc. Cooked lentils provide approximately 4.8 mg of zinc per cup.

5. Chickpeas: Chickpeas also offer a decent amount of zinc, with about 2.5 mg per 100 grams of cooked chickpeas.

Treating Zinc Deficiency

Suspect a zinc deficiency in patients exhibiting any of the symptoms mentioned above. However, indiscriminate zinc supplementation can lead to anemia and imbalanced trace metals. Zinc increases the need for other minerals like selenium and copper, and so zinc supplementaiton alone is best in low doses to not upset mineral balance. Dietary zinc absorption is typically 35-45% efficient but can drop to 10-15% in cases of malabsorption syndromes. Once absorbed, zinc concentrations are regulated by the metal-binding protein, metallothionein. Many zinc-deficient individuals seem to have a metallothionein disorder. Treating mild to moderate zinc depletion may take several months, while severe cases can require a year or more for resolution.

The average American consumes about 10mg of zinc daily, one-third less than the recommended daily allowance (RDA).

Zinc deficiency can often be corrected with supplementation, and many patients previously undergoing extensive therapy and medication programs respond well to less intensive treatments once zinc levels are restored. However, zinc deficiency, like diabetes, requires lifelong management—discontinuing treatment usually leads to the return of symptoms.

Recomended form of Zinc: Zinc bisglycinate:

Dr. Clark's Zinc Bisglycinate

Sources

1. Walsh, W. J. (2014). Nutrient power: Heal your biochemistry and heal your brain. Simon and Schuster.

2. Portbury, S. D., & Adlard, P. A. (2017). Zinc signal in brain diseases. International journal of molecular sciences, 18(12), 2506.

3. Prasad, A. S. (2008). Zinc in human health: effect of zinc on immune cells. Molecular medicine, 14, 353-357.

4. Bhowmik, D., Chiranjib, K., & Kumar, S. (2010). A potential medicinal importance of zinc in human health and chronic. Int J Pharm, 1(1), 05-11.

5. Grahn, B. H., Paterson, P. G., Gottschall-Pass, K. T., & Zhang, Z. (2001). Zinc and the eye. Journal of the American College of Nutrition, 20(2), 106-118.