Uric acid is a natural waste product formed when the body breaks down purines, compounds found in certain foods and produced by cells. The kidneys play a significant role in maintaining the body’s balance of uric acid, primarily filtering it from the blood and removing it through urine.
Uric Acid and Kidney Function
Uric acid is the end product of purine metabolism. Purines are compounds present in body cells and many foods, including meats, seafood, and some vegetables. When purines are broken down, they produce uric acid, which circulates in the bloodstream.
Healthy kidneys effectively manage uric acid levels. They filter nearly all uric acid from the blood through glomeruli, tiny filtering units within the kidneys. About 90% of this filtered uric acid is reabsorbed back into the bloodstream in the renal tubules. The remaining uric acid is then secreted into the urine for excretion. This process of filtration, reabsorption, and secretion ensures blood uric acid levels remain within a healthy range, typically 3.5 to 7.2 milligrams per deciliter (mg/dL).
Why Uric Acid Levels Rise
Elevated uric acid levels, known as hyperuricemia, occur due to two primary mechanisms: the body producing too much uric acid or the kidneys not excreting enough. Both factors can contribute to an imbalance.
Overproduction can result from a diet high in purines, found in foods like red meat, organ meats, and certain seafood. Metabolic conditions or rapid cell turnover, such as during chemotherapy, can also lead to increased uric acid synthesis. The enzyme xanthine oxidase converts purines into uric acid.
The more common reason for elevated levels is under-excretion by the kidneys. While kidneys normally excrete about 70-75% of the body’s uric acid, various factors can impair this function. Kidney dysfunction can reduce their ability to filter and excrete uric acid efficiently. Additionally, certain medications, such as diuretics, can interfere with uric acid excretion. Some individuals may also have a genetic predisposition that affects their kidneys’ ability to process uric acid effectively.
Consequences of High Uric Acid
Chronically high uric acid levels can have several negative impacts on health, particularly affecting the kidneys. One significant consequence is the formation of uric acid kidney stones. These stones develop when uric acid crystallizes in the urinary tract, leading to sharp, severe pain in the side and lower back.
Sustained hyperuricemia can also contribute to or worsen chronic kidney disease (CKD). High uric acid levels may induce inflammation and oxidative stress within kidney tissue, potentially leading to long-term damage and a decline in kidney function. This can create a cycle where impaired kidney function further reduces uric acid excretion, exacerbating the problem.
Although primarily affecting joints, gout is another common manifestation of hyperuricemia. Gout occurs when uric acid crystals accumulate in the joints, causing sudden, intense pain, swelling, and redness, most frequently in the big toe. Its underlying cause is directly linked to the body’s inability to manage uric acid levels effectively.
Approaches to Managing Uric Acid
Managing elevated uric acid often involves dietary adjustments, lifestyle changes, and, when necessary, medical interventions. Dietary modifications are a first step. Limiting foods high in purines, such as red meat, organ meats, and certain shellfish, can help reduce uric acid production. Increasing the intake of fruits, vegetables, and low-fat dairy products is also recommended. Maintaining good hydration by drinking plenty of water helps the kidneys flush out uric acid more efficiently.
Lifestyle adjustments further support uric acid management. Achieving and maintaining a healthy weight can improve kidney function and help regulate uric acid levels, as excess body fat may contribute to higher production and decreased excretion. Regular physical activity is also encouraged. Avoiding excessive alcohol consumption is important, as alcohol can trigger increased uric acid levels and dehydration.
For some individuals, medical interventions become necessary to lower uric acid. Medications like allopurinol and febuxostat inhibit xanthine oxidase, an enzyme involved in uric acid production, reducing the overall amount. Other medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or colchicine, may be prescribed to manage acute symptoms of conditions like gout flares. All medication for uric acid management should be used under the guidance of a healthcare professional.