A diet that’s best known for promoting heart health may also significantly reduce blood levels of uric acid – a key factor in the development of gout, according to a new study published online recently in Arthritis & Rheumatology. The DASH (Dietary Approaches to Stop Hypertension) diet, which emphasizes fresh fruits and vegetables, whole grains and low-fat dairy products, was developed nearly 20 years ago by a government-funded research collaborative to reduce high blood pressure. In the new study, researchers found that in some cases, DASH may also lower uric acid levels almost as well as medications do.
Gout occurs when excess uric acid builds up in the blood and forms needle-like crystals that are deposited around the joints – often in the big toe, but also in the feet, ankles, knees, wrists and elbows – leading to episodes of intense pain, redness and swelling (called flares). It affects more than 8 million adults in the U.S., and the numbers are increasing sharply – due, experts say, to rising rates of obesity, an aging population as well as other factors.
Diet has long been implicated in gout, particularly as a flare trigger; red meat, alcohol (beer and spirits) and some types of seafood are high in purines, which are converted by the body into uric acid. People with gout are usually told to avoid these and most other foods high in purines.
But the researchers point out that there is no solid scientific evidence showing that a diet low in purines actually lowers uric acid (although they note there is some weak evidence, such as observational studies). They hypothesized that the DASH diet might be an exception because it is low in purines and high in vitamin C and low-fat dairy, both of which have been found in studies to be helpful in reducing uric acid in the body.
To find out, lead study author Stephen Juraschek, MD, from the Johns Hopkins University School of Medicine, and colleagues analyzed a portion of the data from the original DASH clinical trial, which was published in 1997. In that study, more than 400 participants ate either the DASH diet or a typical American diet for three months. For each of the three months, the DASH and the typical American diets contained varying levels of sodium, ranging from low (about half a teaspoon) to high (1.5 teaspoons), with the highest level similar to what most Americans consume in a day.
At the time, the results of the original study were groundbreaking. They showed that the DASH diet significantly reduced high blood pressure and improved health overall. Today, DASH is considered the prototype of a healthy diet. (In 2016, it was named “best diet plan” by U.S. News & World Report for the sixth year in a row.)
For the follow-up study, Dr. Juraschek and his team looked at a smaller number of patients who consumed the DASH diet or the control diet with varying amounts of salt for three months. But instead of studying blood pressure, the researchers looked at uric acid levels.
Normal blood uric acid values for men and postmenopausal women can range from 3.5 to 7.2 milligrams per deciliter (mg/dL); for premenopausal women, the values are a bit lower. For patients with existing gout, the goal is to get uric acid to a level below 6 mg/dL.
The researchers found that the DASH diet led to a modest overall drop in uric acid of 0.35 mg/dL. But the reduction was more significant when starting levels were higher. For patients with the highest starting levels – greater than 7 mg/dL – uric acid concentrations dropped by as much as 1.3 mg/dL – an effect on a par, the researchers say, with uric acid-lowering drugs.
Against expectations, higher sodium consumption didn’t increase uric acid levels – it actually decreased them, especially in patients with high blood pressure. The researchers say they aren’t sure why this is the case, but other studies have shown similar results.
Still, they caution that no one should eat more salt in an effort to reduce uric acid. For one thing, the reductions were small – 0.3 to 0.4 mg/dL. More important, consuming excessive sodium can have harmful consequences on other aspects of health, especially blood pressure, Dr. Juraschek says.
But the researchers do recommend the low-sodium DASH diet to reduce uric acid and high blood pressure. Hyon Choi, MD, a leading gout expert at Massachusetts General Hospital in Boston and a study co-author, says his group has recently completed an analysis of data from the Nurses’ Health Study, which has followed 100,000 nurses for over 26 years. According to that analysis, the DASH diet appears to reduce not only uric acid levels but also the risk of developing gout.
“The DASH diet appears to carry remarkable promise in gout care by improving both uric acid levels and cardiovascular comorbidities, particularly hypertension, which affects 74 percent of gout patients,” Dr. Choi says.
N. Lawrence Edwards, MD, a professor of medicine at the University of Florida in Gainesville and chairman of the Gout & Uric Acid Education Society, isn’t so sure.
“Gout can hardly ever be effectively managed by diet alone,” he says. “The press and internet have overemphasized the treatment impact of dietary restrictions [and underemphasized] compliance with urate-lowering medications. [Also], this sub-study of the DASH-sodium trial excluded patients with significant cardiovascular, renal or diabetic disease. This makes interpretation of the study somewhat difficult since gout patients are frequently afflicted with these three comorbidities.”
Jasvinder Singh, MD, a professor of medicine at the University of Alabama, Birmingham, whose research focuses on analysis of rheumatological clinical trials, doesn’t entirely agree.
“The findings from the study are quite informative,” he says. “These findings provide patients with evidence that a specific diet can lower serum urate. These findings may be helpful to patients with gout who are asking the question, ‘What can I do to help my gout?’ or people who have a family history of gout and want to do something to lower their risk of getting gout in the future.”
Author: Linda Rath for the Arthritis Foundation