High uric acid levels in the blood, known as hyperuricemia, can lead to the formation of urate crystals in the joints. This causes inflammation and pain, especially in small joints such as the knuckles of the fingers or toes.
In addition to peripheral joint pain, some people experience lower back pain. In some cases, uric acid-associated inflammation can affect the spine or coexist with other inflammatory diseases such as spondyloarthritis.
The relationship between joint inflammation and lower back pain is understood to be part of a systemic process. Gout and other inflammatory arthritis are linked to metabolic syndrome, obesity, and diets high in purines, which contribute to elevated blood uric acid levels.
A 36-hour fast, when practiced in a controlled manner, has shown in preliminary studies a reduction in inflammatory markers and improved metabolic regulation. However, in the short term, it may temporarily increase uric acid levels due to competition with ketone bodies for renal excretion.
Therefore, although prolonged fasting may offer benefits in reducing inflammation and improving metabolic health, it should be practiced with caution and, if possible, under medical supervision in people with a history of gout or hyperuricemia.
Sources cited:
1) Mayo Clinic. *Gout: Symptoms and causes*. https://www.mayoclinic.org/diseases-conditions/gout/symptoms-causes/syc-20372897
2) National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). *Hyperuricemia and Gout*. https://www.niddk.nih.gov/health-information/kidney-disease/hyperuricemia-gout
3) Longo VD, Mattson MP. *Fasting: Molecular Mechanisms and Clinical Applications*. Cell Metab. 2014. https://doi.org/10.1016/j.cmet.2013.12.008