Zinc: properties, benefits and effects

Zinc is present in every cell of the body and is one of the elements at the base of over 200 enzymes or, better, it is the mineral that more than others affects the greatest number of enzymatic reactions.
Zinc is also needed for the proper activity of many hormones, including thymic hormones, insulin, growth hormone, and sex hormones.
The average organism of an adult contains a total of 1.4-2.5 g, mostly stored in the muscles (65% of the total) and concentrated in particular in red and white blood cells. Other high zinc content tissues include bone, skin, kidney, liver, pancreas, retina, and prostate. The recommended daily dose for adults is 15 mg.

Food sources

The best known sources of zinc are oysters, however it is also present in relatively high concentrations in other crustaceans, fish and red meats. Good concentrations are found in various vegetables, such as whole grains, legumes, nuts and seeds. It should be noted, however, that the zinc of plants is less bioavailable since, by binding to phytic acid (a compound of the Fibre) to form an insoluble zinc-phytate complex, it is not absorbed.

Zinc content in some foods

The values ​​are expressed in mg per 100g of food

Signs and symptoms of deficiency

Severe zinc deficiencies, although infrequent, are characterized by skin changes, diarrhea, hair loss, mental disorders and recurrent infections due to weakened immune functions [1].
The clinical conditions associated with zinc deficiency are as follows.

• Frequent and / or severe infections
• Disorders of sleep and behavior
• Slow wound healing
• Psychiatric diseases
• Inflammatory bowel diseases
• Malabsorption syndrome
• Decreased appetite, anorexia
• Growth retardation
• Loss of sense of smell and taste
• Delayed sexual maturation
• Night blindness
• Impotence, infertility
• All dermatological disorders
• Abnormal menstruation
• Dandruff and hair loss
• Alcohol abuse
• Diseases of the connective tissue
• Use of diuretics
• Rheumatoid arthritis

Moderate zinc deficiency can be reflected in increased susceptibility to infections, poor wound healing, decreased sense of smell and taste, some minor skin diseases, such as acne and eczema, and psoriasis. Other diseases often related to zinc deficiency include: reduced night vision or in poor lighting conditions, growth retardation, testicular atrophy, oral mucosal ulcers, white coating on the tongue and accentuated halitosis [1] [2] [3] [4] [5].
The appearance of white spots on the nails can also be a sign of a low zinc level [6].
The best laboratory method for determining the status of zinc is by measuring its quantity in white blood cells (leukocyte zinc) [1] [7].

Oysters are by far the richest food in zinc

Recommended daily dose

The population recommended intake levels (PRI) for zinc (SCF, 1993) for adult males and females is 9.5 mg / day and 7.0 mg / day, respectively. Minimum intake levels are 7.3 mg / day and 5.5 mg / day for males and females, respectively.In the United States, new guidelines recommend daily doses of 11 mg / day and 8 mg / day for men and women, respectively.
* Source EFSA

Beneficial effects

An adequate level of zinc is essential for good health. The positive effects of this mineral are manifold, since there are numerous enzymes and functions of the organism in which it participates.
The greatest benefits were seen on the immune system, wound guanglOne, sensory function, sexual function and skin health.
Adequate zinc levels are required for proper immune function; a zinc deficiency can cause, in fact, a greater predisposition to infections.
Zinc is essential for protein synthesis and cell growth and is therefore necessary for wound healing.
Zinc is essential for the good functioning of sight, taste and smell; a lack of it can compromise these senses. Night blindness is often caused by a zinc deficiency. Loss of taste and / or smell is a common problem in the elderly; in some individuals, zinc supplements sharpen the sense of smell and taste.
Zinc is important for the proper function of male sex hormones. Its deficiency can contribute to prostatic hypertrophy and lead to male infertility (the lack of zinc can cause a reduction in the number of spermatozoa).
The importance of zinc in normal skin function is well known.

Main uses

Zinc has numerous uses; the main ones concern: cases of deficiency, pregnancy, disorders of male immune or sexual function, rheumatoid arthritis and other inflammatory diseases, acne, macular degeneration, Alzheimer's disease and Wilson's disease.

Zinc deficiency

Zinc deficiency is caused by a reduced intake and / or use of zinc. Many diseases are associated with a deficiency of this mineral.
Some conditions, listed below, are related to reduced absorption.

• Nervous anorexia
• Irregular diet
• Lack of protein
• Vegetarianism
• Alcoholic cirrhosis
• Old age
• Acute infections / inflammations
• Alcoholism
• Increased body losses (starvation, burns after trauma)

Some conditions, listed below, are associated with reduced zinc absorption.

• Diabetes mellitus
• High fiber diet
• High calcium: zinc dietary ratio
• High dietary iron: zinc ratio
• Alcoholism
• Chelating agents
• Acrodermatite enteropatica
• Dialysis
• Achlorhydria / hypochlorhydria
• Liver disease
• Celiac disease
• Inflammatory bowel diseases
• Diarrhea
• Intestinal resection
• Chronic blood loss
• Short bowel syndrome
• Pancreatic insufficiency

Pumpkin seeds are very rich in zinc

Male sexual function

Zinc is perhaps the most important trace mineral in male sexual function. It plays a role in every aspect of male reproduction, including hormone metabolism, sperm maturation and mobility [13]. A zinc deficiency is also characterized by a drop in testosterone levels and sperm count. Zinc levels are typically lower among infertile men with oligospermia (reduced sperm count): this means that a deficiency in this mineral can contribute to infertility.
Several studies have evaluated the effects of zinc supplements on sperm count and mobility [14] [15] [16] and the results confirm the use of supplements in oligospennia therapy, especially in the presence of low testosterone levels. The efficacy of zinc is best illustrated by an examination of a study carried out on 37 sterile men for over 5 years, whose sperm count was inferior to 25 million / mI. Blood testosterone levels were also measured [16]. Patients received zinc sulfate supplements (60 mg per day of elemental zinc) for 45-50 days. Among the 22 patients with initially low testosterone levels, the average sperm count rose from 8 to 20 million; testosterone levels also increased. So, Nine of their 22 companions were fertilized during the study. This is a remarkable achievement given the long-term nature of infertility and the immediate results achieved. In contrast, the 15 men with normal testosterone levels did not experience any changes, nor did any new pregnancy occur despite a slight increase in sperm count.

Acne

Several double-blind studies have demonstrated the efficacy of zinc also in the treatment of acne, with results similar to tetracycline in the treatment of superficial acne and with even better results against deep acne [20 [21] [22]. Although some studies of zinc in acne patients have not reported such improvements, the non-homogeneous results may be due to the different dosage or form of zinc used. Per example, studies performed with zinc citrate or zinc gluconate show improvements similar to those determined by tetracidin, while those with zinc sulfate obtain less benefits [23] [24] due to the reduced absorption of zinc sulfate. To date, there have been no studies on other absorbable forms of zinc, such as picolinate,
Although some of the study participants showed dramatic and sudden improvements, most of the subjects usually needed 12 weeks of taking the supplements before they had positive results.
Because these forms of zinc are absorbed more effectively than the forms used in successful studies, it is possible that they produce even better results. The safe and effective dose of zinc is between 30 and 45 mg per day.

Macular degeneration

Zinc has somewhat positive effects in the treatment of macular degeneration. The macula is the portion of the eye responsible for good eyesight; its degeneration is the leading cause of vision loss in the United States and Europe among people aged 55 and over. In a study conducted in the Department of Ophthalmology at the Utah School of Medicine, 151 patients with rnacular degeneration received 100 mg of zinc or a placebo [25]: the group treated with the zinc experienced significantly less vision loss.

Warnings and Precautions

The main toxic effects of zinc occur as a consequence of prolonged intakes of dosages higher than 150 mg per day. Among these effects are copper deficiency anemia, reduced HDL cholesterol levels, and depression of immune function. Acute toxicity is quite rare, as ingesting doses that cause toxic symptoms (2 g / kg body weight) usually causes vomiting. The range from severe deficiency to toxicity is referred to as the 'nutrition gray area'; somewhere between these extremes lies the optimal value of zinc intake. Per zinc, this gray area is quite large. This is probably the least toxic trace element.
When taken on an empty stomach (particularly in the form of zinc sulfate), the supplement can cause gastrointestinal upset and nausea.

Interactions

Zinc competes with copper for absorption. Other minerals (especially calcium and iron) can negatively affect zinc absorption if taken in high doses.
Zinc supplements should be consumed away from high-fiber foods to promote better absorption.

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