In a recent study published in Scientific Reports, researchers performed a meta-analysis to evaluate the effects of the ketogenic diet (KD) and dietary approach to stop hypertension (DASH) diet on serological uric acid (UA) levels.
Study: The effect of dietary approaches to stop hypertension and ketogenic diet intervention on serum uric acid concentration: a systematic review and meta-analysis of randomized controlled trials. Image Credit: Alexander Rutz / Shutterstock.com
Hyperuricemia is a major risk factor for gout onset and has been linked to cardiometabolic diseases.
Weight loss measures are considered key contributors to lowering the risk of hyperuricemia, as UA levels often fluctuate according to different dietary habits. In fact, dietary treatments have been shown to alter hyperuricemia and alleviate gout symptoms significantly. Recent research has linked the DASH diet, which includes vegetables, fruits, moderate-protein, and low-fat milk products, to lower UA.
KD is a high-fat, moderate-protein, and low-carbohydrate diet commonly used to lose weight and treat neurological diseases. Numerous observational-type studies have documented transitory hyperuricemia in the ketosis stage of KD; however, the relationship between KD and UA levels remains unclear. Furthermore, serum UA alterations following very low-calorie KDs (VLCKD) are debated.
About the study
PubMed, Web of Science, Scopus, and Embase databases were searched through March 2023 without language restrictions for randomized controlled trials (RCTs), in which DASH or KD diets were assigned to adults for at least two weeks. In addition, the references to relevant RCTs were manually searched for additional articles.
The Cochrane risk of bias tool for RCTs (RoB-2) was used to assess bias risks, whereas the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to assess evidence quality. Two researchers independently screened the data, with any disagreements resolved by discussion with two other researchers.
Random-effects modeling was performed to calculate the summary effect. A subgroup analysis based on different amounts of calorie intake in KDs was used to identify heterogeneity sources in the included studies. A sensitivity analysis was also performed to assess the effects of individual RCTs on the pooled estimates.
Only RCTs including adults and comparing the effects of ketogenic or DASH diets on UA levels with control groups were included. RCTs that included pregnant women or individuals with conditions such as epilepsy and malignancy that could alter serological UA levels, those with an intervention period of fewer than 14 days, and KD studies with unattained ketosis were excluded from the analysis. In addition, animal or in vitro studies, book chapters, and records with generic or incomplete data were excluded.
DASH diet reduces UA levels, KD is not effective
A total of 26,915 records were initially identified. After eliminating irrelevant and duplicate articles, the titles and abstracts of 13,758 studies were screened, following which 257 studies underwent full-text screening. After applying the eligibility criteria, 10 RCTs, including four and six RCTs intervening with the DASH diet and KD, respectively, were considered for the final analysis.
The pooled estimate for the DASH diet clinical trials, which included 590 individuals, showed a significant reduction in serological UA after a minimum of 28 days of interventions. In contrast, the pooled estimate of the six KD RCTs documenting data from 267 individuals showed non-significant changes in serological UA levels. Likewise, the subgroup analysis of VLCKD RCTs yielded non-significant UA reductions.
The DASH diet, which includes foods with a low glycemic index, like certain fruits and dairy products, has been shown to reduce UA levels without altering insulin or glucose levels. Purine-free milk-origin proteins such as lactalbumin and casein, as well as other components of the DASH diet, like vitamin C, have also been found to have UA-lowering effects.
The lower UA levels following VLCKD may be due to the limited ability of the body to maintain circulatory ketone bodies during fasting or near-fasting diets by limiting their renal elimination. The discrepancies in calorie, fat, and carbohydrate intakes during the trials may have contributed to significant variability across KD studies.
The DASH diet appears to lower blood UA levels; therefore, integrating this diet into management regimens for individuals with hyperuricemia conditions, including gout, may have beneficial outcomes. Although blood UA levels were unaffected by KD, the very low-calorie KD appears to provide UA-lowering effects, which requires further investigation.
Future research, including larger sample sizes and more consistent populations, could assess the dose-response relationships between the DASH diet and serological UA levels and other diets, including the Mediterranean and vegetarian diets, to identify which diet is best for lowering serum UA.
- Gohari, S., Ghobadi, S., Jafari, A. et al. (2023). The effect of dietary approaches to stop hypertension and ketogenic diet intervention on serum uric acid concentration: a systematic review and meta-analysis of randomized controlled trials. Scientific Reports 13(10492). doi:10.1038/s41598-023-37672-2