Zinc, an effective trace element against psoriasis?

Thepsoriasis is a chronic inflammatory skin disease that affects nearly 2% of the French population. It is the third most common skin disease after acne and eczema. It manifests itself through the appearance of thick red patches covered with white dead skin known as scales. These patches can be more or less itchy.

Regarded as a autoimmune disease, psoriasis is a result of a malfunction in the immune system. For reasons still unknown, immune cells secrete inflammatory molecules into the skin. These molecules stimulate the proliferation of keratinocytes (instead of renewing in 21 days, they renew in 7 days) which accumulate on the skin's surface: this ishyperkeratosis. This skin condition appears in flare-ups and occurs in individuals with a genetic predisposition and under the influence of certain factors.

It's worth noting: an autoimmune disease results from a malfunction of the immune system. It attacks the normal constituents of the body.

Due to the poor understanding of this disease, people with psoriasis are subject tostigmatisation, leading to social isolation. Therisk of anxiety and depression is therefore very high. Moreover, psoriasis is not limited to the skin as it can manifest in the joints, referred to aspsoriatic arthritis.

Zinc is a crucial micronutrient, found in small quantities within the human body, less than 50 mg/kg. It is vital for the body's health due to its critical roles in growth and development, bone metabolism, the central nervous system, immune function, and wound healing, which is the focus of this article.

Zinc is a vital cofactor for the function of over 10% of proteins encoded by the human genome, representing no less than 3000 proteins and enzymes ! Zinc-dependent proteins play numerous indispensable roles within cells, such as transcriptional regulation, DNA repair, cell death, metabolic processing, regulation of the extracellular matrix (ECM), and antioxidant defence.

It should be noted, this trace element cannot be stored by the body. Therefore, to reap its benefits, regular consumption of zinc-rich foods is essential. The food richest in zinc is the oyster, but there are others such as the offal, red meat, wholemeal bread and eggs. The vast majority of zinc present in the human body is stored in the skeletal muscles (60%), but reserves are also present in the bones (30%), the skin (5%), the liver and other organs (2 to 3%).

A study has shown that the serum zinc levels (82.6± 1.93 µg/dl) of individuals suffering from psoriasis were lower than those of normal controls. Following oral zinc supplementation, these levels gradually increased to reach (99.3± 6.01 µg/dl) in the second month (p<0.05) and climbed to 103.6 µg/dl in the following months. Simultaneously, the clinical manifestations of psoriasis improved and eventually disappeared.

The maximum tolerable intake, defined as the highest daily dose unlikely to have adverse health effects, is 40 mg of zinc. Nausea, vomiting, diarrhoea, headaches, and cramps are some of the symptoms of zinc toxicity, beyond this 40 mg limit.

To alleviate psoriasis flare-ups, the optimal solution remains to combine external and internal approaches. Thus, dermatologists typically prescribe a zinc-based cream along with zinc-rich dietary supplements. Additionally, through topical application, creams rich in Vitamin A and/or salicylic acid derivatives are also relevant for soothing psoriasis.

• DEREAGZI H. & al. Zinc in treatment of psoriasis. Journal of Islamic Academy of Sciences (1991).