Pilot Study: DASH Diet Reduces Serum Urate in Patients with Gout
Key findings
- This pilot study evaluated how an intervention patterned on the dietary approaches to stop hypertension (DASH) diet affected serum urate levels in people with gout not using urate-lowering therapy
- 43 participants were randomly assigned to receive $105/week for four weeks to buy groceries of their choice with dietitian guidance, then cross over to self-directed grocery (SDG) buying without a stipend, or the opposite
- In period 1, dietitian-directed groceries (DDG) lowered serum urate by 0.55 mg/dL and SDG had no effect; in period 2, the difference between groups was the opposite: SDG reduced serum urate by 0.48 mg/dL and DDG reduced it by 0.05 mg/dL (P for interaction by period = 0.11)
- 81% of participants said the DASH diet was easy to follow, 81% said they enjoyed it and 74% said they were likely to continue it after the trial
- There was no washout period between interventions in this trial, which probably led to a carryover effect
The dietary approaches to stop hypertension (DASH) diet, which emphasizes fruit, vegetables and low-fat dairy products, has been proven to reduce blood pressure and low-density lipoprotein cholesterol. Massachusetts General Hospital researchers recently reported in BMJ that men who follow the DASH diet are less likely to develop new-onset gout, and in several studies, they've shown that DASH interventions lower serum urate in adults without gout.
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Now, Hyon Choi, MD, program director of the Clinical Epidemiology Program and clinical rheumatologist with the Division of Rheumatology, Allergy and Immunology (RAI), and colleagues have presented evidence that a DASH-patterned diet improves serum urate in patients with gout. Their report on a four-week randomized pilot study appears in Nutrients.
Study Methods
The DIGO Trial (Dietary Approaches to Stop Hypertension Diet Effects on Serum Uric Acid in Adults with Hyperuricemia and Gout) recruited 43 adults from the community (19% female, 49% Black, average age 59) who had a self-reported diagnosis of gout and serum urate ≥7 mg/dL. Individuals who used urate-lowering therapy or planned to start it were excluded.
The participants were randomly assigned to either of two 4-week interventions:
Dietitian-directed groceries (DDG)—Participants were given $105/week for groceries. The food was ordered from a national retailer with the guidance of a dietitian (initially in person, then through weekly telephone calls).
Participants chose their own food in ways concordant with the DASH diet: 5–7 servings/day of grains, 4 servings/day of fruit, 4 servings/day of vegetables, 1–2 servings/day of lean meat, 2 servings/day of low-fat dairy and <0.5 servings/day of high-fiber foods. They were asked to restrict alcohol, sugar-sweetened beverages, sweets, red meat, organ meats and shellfish. Food orders were selected to be low in fat, saturated fat and cholesterol and to provide <2300 mg/day of sodium.
Food was delivered to the research center for pick-up by the participants, and compliance with ordering was assessed in that way. Participants were asked to avoid eating non-study foods. Participants were also asked to report how much, and which components, of the groceries they consumed.
Self-directed groceries (SDG)—No grocery stipend was provided and participants ordered their own groceries.
After the first month, the participants immediately crossed over to the opposite intervention. The first participant was enrolled on August 7, 2018, and data collection ended on July 23, 2019. No participant dropped out.
Serum Urate
Period 1:
- DDG—0.55 mg/dL reduction in serum urate
- SDG—0.0 mg/dL reduction
Period 2 (after crossover):
- SDG—0.48 mg/dL reduction
- DDG—0.05 mg/dL reduction (P for interaction by period = 0.11)
Compliance
Participants completed food frequency questionnaires at the end of each period. During the DDG condition, intake of saturated fat and cholesterol significantly decreased and daily servings of fruit, vegetables and beans significantly increased (all P-values ≤0.002). Urine testing showed no change in urate excretion, potassium or urine pH, but DDG was associated with significantly reduced urine sodium excretion.
Acceptability
81% of participants said the DDG assignment was easy to follow and 81% said they enjoyed the diet. 74% said they were likely to continue the diet beyond the conclusion of the trial. Only 21% reported wasting or storing food and only 7% reported supplementing with non-study foods.
Continued Scrutiny Needed
The DIGO trial did not include a washout period between interventions because SDG-to-DDG was inherently a delay of the intervention and DDG-to-SDG was a washout of the intervention. However, participants initially assigned to DDG could have continued eating a DASH diet during the SDG condition. Alternatively, once there was a diet-induced reduction in serum urate, there might have been a physiological lag in its return to baseline, particularly without controlled eating.
However, these hypotheses do not explain the near-absent effect of the DASH diet in the SDG-to-DDG group. A definitive trial to establish the diet's efficacy as a treatment for gout would require providing all the food that participants consume, similar to the original DASH trials.
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