Fibromyalgia is a complex and common chronic pain disorder that affects 12 million Europeans. Fibromyalgia causes persistent widespread pain in muscles, tendons, ligaments, and joints, as well as widespread tenderness to touch and the presence of extreme fatigue and weakness.

Histamine is a molecule derived from an essential amino acid, histidine. It is stored in mast cells and basophils and is excreted through the intestine, being degraded as it passes through the intestinal mucosa by the enzyme Diamine Oxidase (DAO), which is found in this area. If there is any alteration in its metabolism and normal concentrations of histamine in the blood (50-70 mg/l) are not maintained, the free circulation of this amine in high concentrations triggers undesired effects, such as migraine, fibromyalgia, asthenia and atopy.

DAO deficiency is an alteration in the metabolism of dietary histamine that occurs when there is little activity of the DAO enzyme. The low activity of the enzyme causes that a concentration considered normal of histamine from food cannot be metabolized and a transepithelial penetration of exogenous histamine occurs. In this way, histamine passes into the bloodstream, increasing its plasma concentration and once located freely in the blood, it is distributed throughout different parts of the body, producing adverse effects.

One of the factors that causes DAO deficiency is genetics. The genetic sequence of DAO is found in a fragment located on chromosome 7 (7q34-q36) of the human genome. There are 85 single nucleotide variants (SNPs) located and identified in the human DAO gene (AOC1). Seven of these SNPs produce amino acid substitution, being candidates to cause alterations in the metabolic capacity of the enzyme.

Since histamine accumulation can trigger fibromyalgia, and the enzyme DAO has been shown to degrade histamine, oral supplementation with DAO food supplements, prepared from pig kidney, is suggested as a treatment for fibromyalgia.

The objective of this study is to analyze whether DAO enzyme supplementation reduces the characteristic symptoms of fibromyalgia. In addition, the prevalence of DAO deficiency in women with fibromyalgia will be identified by genetic analysis of DAO deficiency from a saliva sample. It will also be evaluated if patients require a lower intake of analgesics after supplementation with the enzyme DAO.

Inclusion Criteria:

• Female
• Age between 30 and 59 years (included)
• Diagnosis of fibromyalgia
• Must sign an informed consent
• Able to follow-up at 2 and 6 months

Exclusion Criteria:

• Pregnant or possibly pregnant
• Patients with change of pharmacological treatment in the last 3 months
• Patients with DAO enzyme treatment
• Patients diagnosed with other severe diseases (i.e. cancer, cardiovascular disease, autoimmune disease or metabolic disease)
• Patients with multiple chemical sensitivity