The study was designed as a randomized double-blind placebo-controlled clinical trial with 8-week Vitamin D3 and physical activity intervention. The protocol was approved by Independent Bioethics Committee for Scientific Research at Medical University of Gdańsk (No. 525/2018), in accordance with the Declaration of Helsinki. We enrol 40 patient (aged ≥ 35), Patients diagnosed with chronic pain in the lumbar spine, qualified for surgical treatment at the Department of Neurosurgery Medicinal Unit in Gdańsk. Participation in the study was voluntary, and the condition for participation was obtaining informed consent from the patient.

Before starting supplementation, a blood sample was taken from patients to determine the status of vitamin D3, measurements of hydroxylated vitamin D at position 25 (25OHD3) and monitoring of inflammatory markers such as Interleukin-6; TumorNecrosisFactor-α. This measurement was performed in the University laboratory in Gdańsk according to a standard, generally accepted method for the determination of a given compound. The blood sample was taken by a qualified nurse. This measurement was repeated to control vitamin D levels and markers of inflammation:

• After 6 weeks of supplementation (before surgery);
• After 2 weeks of supplementation (after surgery);

Patients was supplemented with vitamin D or placebo for 6 weeks before surgery and was continue supplementation for 6 weeks after surgery. According to the value of the Body Mass Index, the dose of vitamin D will be appropriately selected for each group:

• Group 1 BMI 19-25 - 4000 IU
• Group 2 BMI 25-29,9- 6000 IU
• Group 3 BMI >30- 8000 IU

A person was appointed to coordinate the allocation of patients to the two groups. Patients was not informed whether they are receiving vitamin D or a placebo. The treating doctors, radiology specialists and the rest of the team was not know what group the patient is in. Within individual groups, patients was randomly assigned to:

• Group A - patients supplemented with placebo;
• Group B - patients supplemented with vitamin D3; Patients was informed about the purpose of the research and was receive. The patients diet was monitored during supplementation by a certified clinical dietitian using food diaries. The food diary is a basic tool for monitoring the diet of test subjects. After appropriate training, the respondents are able to fill in the diary on their own, writing down all the meals eaten during the day and snacks with drinks. It is a qualitative and quantitative method that allows you to analyze the diet so far and draw appropriate conclusions.

Patients from both groups who will not have contraindications to exercise, 2 weeks after surgery, was divided into a group for 6 weeks of home routine physical activity and a group not doing any additional physical activity.

• Group A1 - placebo supplementation + exercise
• Group A2 - placebo supplementation + no exercise
• Group B1 - supplementation with vit. D + exercises
• Group B2 - supplementation with vit. D + no exercise

Inclusion Criteria:

• Pain in the lumbar spine that lasts more than 6 months (diagnosed by signs and symptoms, and tests such as magnetic resonance imaging (MRI));
• Failure to respond to medications and physical therapies;
• Visual Analog Pain Scale (VAS), (0-100) score greater than or equal to 50;
• Numerical Rating Scale (NRS);

Exclusion Criteria:

• Rheumatoid arthritis;
• Diagnosed mental illness;
• Drugs;
• Metabolic bone diseases (hypo or hyperparasitism);
• Chronic kidney diseases and diseases affecting vitamin D metabolism (stomach surgery, chronic liver diseases, kidney failure, malabsorption disorders, systemic infection, tumors, etc.)
• Medicines that alter the metabolism of bones such as corticosteroids or bisphosphonates;
• Vitamin D supplements in the last 3 months;
• BMI: less than 19;