Differences in Ferritin, Vitamin D, and Vitamin B12 Between Fibromyalgia Patients and Healthy Individuals: A Systematic Review and Meta-Analysis.

Background: Fibromyalgia-one of the chronic pain syndromes-characterised by pain, fatigue, and tenderness. The role of certain micronutrients like vitamin D, vitamin B12, and ferritin has been previously investigated in many primary studies aiming to assess both their therapeutic and diagnostic potential in the management of fibromyalgia.

Aim: To compare the levels of vitamin D, ferritin, and vitamin B12 between fibromyalgia patients and healthy controls.

Methods: Our study protocol was registered prospectively on PROSPERO (CRD42024585826) and was conducted in accordance with the PRISMA guidelines. Literature search, article screening, and data collection were conducted by two independent investigators. The mean difference along with its 95% confidence interval for each of the three outcomes was pooled under a random effects model.

Results: Twenty-five studies were included in the final analysis; 22 reported vitamin D levels, 5 reported ferritin levels, and 3 reported vitamin B12 levels. Generally, fibromyalgia patients had lower vitamin D and ferritin levels compared with healthy controls (MD = -3.86, 95% CI [-6.99; -0.73] and -14.78, [-18.95; -10.62], respectively). Vitamin B12 showed no difference between the two groups (-20.70 [-51.57; 10.16]).

Conclusion: Vitamin D and ferritin levels were found to be lower in patients with fibromyalgia. Whether vitamin D supplementation improves fibromyalgia symptoms remains under debate. However, we recommend both routine empirical supplementation of vitamin D along with ferritin level testing in all patients. Further studies are needed to confirm whether lower ferritin and vitamin B12 levels contribute to fibromyalgia.