More than 2,000 years ago, “Hippocrates described gout as a disease of kings primarily because it was the wealthy who could afford the ‘rich’ foods, which seemed to precipitate gouty attacks.” Today, however, we can all eat like kings and acquire some diseases of royalty ourselves.
Gout is caused by needle-sharp crystals of uric acid in our joints. Uric acid comes from the breakdown of purines, which are the breakdown product of genetic material—DNA, the foundation of all life. So, “there is no such thing as a purine-free diet, but foods do vary in their purine content.” It was long thought that people with gout just needed to stay away from all high-purine foods, whether from animals, like organ meats, or plants, like beans, but this strategy proved ineffective. Yes, all uric acid comes from the breakdown of purines, so limiting meat makes sense, but plant sources “have largely been exonerated.”
“The association of gout with alcohol intake and increased dietary purine consumption had been known since ancient times, but there were no prospective trial data” to back it up until fairly recently. The Harvard Health Professionals Follow-Up Study, which followed about 50,000 men for a dozen years, found that alcohol intake was “strongly associated with an increased risk of gout.” In terms of food, they found “an increased risk of gout with higher meat consumption or seafood consumption,” but not with higher consumption of purine-rich plant foods. Perhaps this is because the purines in plants are less bioavailable? So, though it had been suggested that gout sufferers should moderate purine-rich animal and plant foods, their “results suggest that this type of dietary restriction may be applicable to purines of animal origin but not to purine-rich vegetables.”
Although it was not surprising that meat, including seafood, had significant associations with the incidence of gout, this lack of effect of purine-rich plant foods was new. There don’t appear to be any long-term studies showing purine-rich plant foods increase risk, though there are still some guidelines continuing to disseminate those outdated recommendations.
Not only has the intake of purine-rich plants not been associated with high uric acid levels, but the vegetable gout sufferers are specifically told to stay away from—mushrooms, peas, beans, lentils, and cauliflower—were actually found to be protective. This may be because foods rich in fiber, folate, and vitamin C appear to protect against uric acid buildup and gout. “Fiber,” for example, “has been recognized as having a potential role in binding uric acid in the gut for excretion.”
Lack of association between purine-rich vegetables and urate could be due to the co-packaging of these “beneficial plant components (such as vitamin C, dietary fiber or some phytochemicals), which may have masked an effect of purine on [uric acid]. Vegetable intake, regardless of purine content, may also be protective as it may increase [uric acid] excretion.”
By changing the pH of our urine, we can change uric acid clearance. Eating an alkaline diet, which was a vegetarian diet in the case of the study I profile in my video, was found “effective for removing uric acid from the body.” Those eating the alkaline diet excreted significantly more uric acid than those eating the acidic diet. As such, uric acid levels in the blood of those eating the acid-forming diet rose within days.
So, one would assume uric acid levels are lower in vegetarians, and, indeed, those eating vegetarian diets long-term were found to have significantly lower levels in their blood. To prove cause and effect, though, you need to do an interventional trial, where you take people, change their diets, and see what happens. Researchers took ten guys to study the build-up of uric acid in their kidneys, kept them on a standard Western diet for five days, and measured their relative supersaturation for uric acid. Then, they tried a vegetarian diet for five days. The result? Within days, the intake of the vegetarian diet led to a 93 percent decline in the risk of uric acid crystallization.
You can do it the other way, too: Take a bunch of people with gout, feed them a big meal of meat, and see if you can trigger an attack. Seven patients were put in a hospital, “stabilized on a low-purine diet and then challenged with a meat-laden dinner.” In response, their uric acid levels shot up, and they started getting gout attacks. Then they added alcohol, and their uric acid levels shot up even further. In all, the researchers were able to trigger gout attacks in six out of the seven patients with just single meals.
Not all animal foods increase gout risk, though. Low-fat dairy products were found to be protective. Given that, we would predict vegans to be at a disadvantage, which is indeed what was found, though all groups tested—meat eaters, fish eaters, vegetarians, and vegans—were within the normal range of around 3.5 to 7.
Should gout patients add milk to their diets? Well, although drinking the equivalent of ten cups of skim milk at a time appears to have an acute lowering effect on uric acid levels, in the long term over months, at the equivalent of two cups a day, there was not a statistically significant lowering effect. Gout patients were given skim milk powder for three months, and it did not appear to help. Though soymilk has also been associated with a lower risk of uric acid buildup, there are no interventional trials to back that up.
The bottom line is that we now have good research on how to reduce risk of gout “without the use of drug treatments through modification of diet.” That’s important, because allopurinol is the “drug of choice.” It’s considered generally safe, but what does it mean when doctors talk about a relatively safe drug? Well, about “2% of patients develop hypersensitivity reactions, which can sometimes be severe and fatal with a mortality rate of ~20%”—and that’s the safe drug. The other leading drug, colchicine, has “no clear-cut distinction between nontoxic, toxic, and lethal doses.”
Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations—2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not to Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.