Low Carb Diet and Gout: Evidence on Uric Acid and Flares

What the Research Shows About Low-Carb Diets and Gout

The two sources reviewed here do not show whether a low carb diet and gout have a beneficial or harmful relationship. The 2019 systematic review contained no ketogenic diet study, and the 2017 laboratory study did not test people with gout.

The systematic review led by Vedder and colleagues examined 18 clinical trials investigating dietary approaches for gout and elevated uric acid. Across all 18 clinical trials, the authors identified no studies investigating a ketogenic diet. The only low-carbohydrate intervention included in the review was a 1977 trial that evaluated a low-carbohydrate, low-calorie diet accompanied by weight loss. That 1977 trial reported a reduction in serum uric acid of approximately 0.5 mg/dL, listed as 0.69 mg/dL in the review outcome table. A single other trial within the review used a dietary protocol consisting of 40 percent carbohydrate. General background on carbohydrate restriction can be found in the overview of a low-carb diet for beginners.

What the Systematic Review Found on Diets and Uric Acid

Dietary trials reviewed by Vedder and colleagues demonstrated variable shifts in serum uric acid (SUA) across several eating patterns. The review included 18 clinical trials in gout or raised uric acid, but the authors judged the studies too heterogeneous to pool into a meta-analysis and rated their overall risk of bias as moderate to high.

The reviewed trials were organized into four intervention categories, reporting the following effects on serum uric acid concentrations:

• Fasting and calorie restriction: Fasting raised serum uric acid levels. A 1967 study included in the review documented rises of 1.1 mg/dL after a 1-day fast and 2.0 mg/dL after a 2-day fast, leading the review authors to state in their abstract that fasting resulted in an increase of SUA. In contrast, one low-calorie diet trial reported that monthly gout attacks fell from 2.1 to 0.6 alongside a 1.69 mg/dL reduction in uric acid.
• Purine-low diets: Three trials were included.3 to minus 2.9 mg/dL.
• Mediterranean-style diets: Four trials were included.3 to minus 2.9 mg/dL range. The authors described the Mediterranean-style diet as the most suitable long-term diet for people with gout and recommended further investigation, while noting that studies examining cardiovascular risk factors were limited and inconclusive.
• Supplements: Five trials examined dietary supplements.

Low-calorie, purine-low and Mediterranean-style diets together produced small but significant changes in serum uric acid, from plus 0.3 to minus 2.9 mg/dL.

Background on the uric acid test is available separately.

The Laboratory Study on Ketones and Gout Inflammation

A 2017 laboratory investigation published by Goldberg and colleagues showed that the ketone body beta-hydroxybutyrate (BHB) suppressed specific inflammatory pathways in animal and cellular models. The study investigated cellular mechanisms related to keto and gout flares rather than clinical diet outcomes in patients.

In the animal phase of the experiment, rats fed a ketogenic diet for one week had less knee joint swelling and lower blood IL-1β after urate crystals were injected into the joint. The researchers observed that BHB suppressed the activity of the NLRP3 inflammasome, a driver of gout-type inflammation. This suppression occurred in laboratory-tested mouse macrophages and neutrophils, as well as in isolated neutrophils taken from human adults aged 18 to 45 and over 65. The study carried distinct boundaries:

• No human dietary trials: The publication did not test a ketogenic diet in humans and did not include people with gout.
• No uric acid measurements: The investigators did not report measuring serum uric acid levels in the animals or human blood samples.
• Injected crystals: The rat model used directly injected urate crystals rather than spontaneous disease onset.
• Alternate mechanisms: The authors stated that the exact mechanism requires further experiments and that observed diet effects could stem from hormonal changes, lipid changes, or glucose limitation.
• Infection testing: Mice fed a ketogenic diet and infected with S. aureus did not have worse disease outcomes.

Background on ketone production is covered in what is ketosis.

Limits of the Evidence

Current scientific literature contains significant methodological gaps regarding how a low-carbohydrate or ketogenic diet affects human gout management.

The 18 dietary trials analyzed in the 2019 systematic review carried moderate to high risk of bias, and study heterogeneity prevented statistical pooling. The review contained no clinical trial evaluating a ketogenic diet in people with gout. The only low-carbohydrate study identified was a 1977 trial that combined carbohydrate restriction with low calories and weight loss.

While Goldberg and colleagues demonstrated that BHB deactivates the NLRP3 inflammasome in laboratory-treated cells, they did not report measuring uric acid levels. In addition, the study authors noted that adherence to a ketogenic diet is difficult and can promote dyslipidemia, which involves abnormal blood fats. Related background is covered in the guide on low-carb diet and cholesterol.

Questions for a Clinician

The following are neutral questions a reader could raise with a clinician:

• Uric acid: What do the available studies suggest about how a given eating pattern relates to serum uric acid?
• Fasting: What does the reported rise in serum uric acid after 1-day and 2-day fasts mean for a particular person?
• Evidence quality: How strong is the evidence for Mediterranean-style or low-carbohydrate diets in gout, given that the review's cardiovascular findings were limited and inconclusive?

Clinician consultation is available at doctors.