Gout and Hyperuricemia
Dietary Approaches to Control Hyperuricemia and Reduce Gout Risk
Lifestyle can have a significant influence on the development of hyperuricemia and gout. Accumulated data from several large epidemiological studies suggest several possible modifications for significant reductions in gout risk (reviewed in Choi 2010):
Exercise daily and reduce weight. Increased adiposity is associated with increased uric acid levels and gout risk.
Limit red meat intake. Beef, pork, and lamb are high-purine foods that can significantly increase gout risk.
Adjust fish intake to individual needs. Carefully balance the benefits of omega-3 fatty acids with the increased gout risk; or consider taking an omega-3 supplement. High quality fish oil supplements are highly purified and the purine content in these oils is either undetectable, or present in trace amounts that pose no risk of raising gout levels.
Drink skim milk or consume other low-fat dairy products. Dairy consumption is inversely associated with gout risk.
Consume vegetable protein, nuts, and legumes. Nuts and legumes are good sources of non-uricemic protein; legumes and vegetables (even those high in purines) are not associated with gout risk.
Reduce alcohol intake. Moderate alcohol consumption has cardiovascular benefits, but beer and spirits significantly increase gout risk. Red wine, on the other hand, appears not to increase gout risk.
Limit intake of sugar-sweetened beverages. Fructose in these beverages might increase hyperuricemia and gout risk. Although fruits also contain fructose, it is usually present at lower levels and most have health benefits that justify their consumption.
In addition to these diet and lifestyle changes, several individual dietary factors may reduce hyperuricemia or gout risk:
Vitamin C is an essential water-soluble antioxidant vitamin in humans, which has been shown in laboratory tests to exert a uric acid-lowering effect by inhibiting the enzyme xanthine oxidase (Feigelson 1952). In a comprehensive review of 13 randomized controlled trials of vitamin C supplementation in a total of 556 adults with normal kidney function, an average reduction in blood uric acid of 0.35mg/dL was observed for an average dose of 500 mg/day for a median duration of 30 days (Juraschek 2011). The most significant reductions were observed in persons with higher initial baseline uric acid concetrations ( patients with a blood uric acid level of >4.85 mg/dL saw a 0.78 mg/dL reduction). In a large study (184 healthy subjects), vitamin C also increased the glomerular filtration rate (the rate at which blood is filtered in the kidney and a measurement of kidney function ) when compared to the control group (Huang 2005). Future trials are necessary to determine whether vitamin C intervention can prevent the incidence and recurrence of gout. Plasma levels of vitamin C are also inversely associated with blood pressure (Bates 1998; Block 2008), which may be an independent risk factor for gout.
Cherries are a traditional gout treatment rich in polyphenol antioxidants (Jacob 2003; Fam 2005), and a small set of clinical cases in the 1950's documented decreased duration and severity of gout attacks in three people on cherry-supplemented diets (Blau LW 1950). Two more recent investigations have demonstrated a potential role of cherries in the management of gout, although they present conflicting mechanisms for this action. After a single dose of 280 g cherries, the blood urate levels in 10 healthy women dropped by 14% after 5 hrs, while urinary urate levels increased (Jacob 2003). Markers of inflammation (CRP) also decreased slightly. A second study of 100 patients with recurrent gout taking 15ml/day of cherry juice concentrate for 4-6 months also revealed decreases in markers of inflammation, as well as a >50% reduction in the number of acute gout attacks for 92% of treated patients (Jancin 2010). However, uric acid levels were not lowered in this group, and averaged 7.8 mg/dL. Cherry consumption has also been observed to increase in blood uric acid (Howatson 2010). Although it appears that cherries may reduce the frequency of gout attacks, the mechanism for this action clearly does not depend solely on lowering blood uric acid levels.
More than 50% of Americans drink coffee, and the average per capita intake is 2 cups per day (Salazar-Martinez 2004). Coffee contains both caffeine and polyphenolic antioxidants that may have independent roles in the reduction of gout risk. The relationship between coffee consumption and the risk of gout has been examined in two large observational studies. In the Nurse's Health Study, 89,433 women were tracked over 26 years for their consumption of coffee – those who consumed more coffee had a lower risk of gout (Choi 2010). The largest reductions in risk were observed in women who consumed over 4 cups of caffeinated coffee per day (-63%), although modest consumption of decaffeinated coffee (>1 cup/ day) reduced gout risk by 23%. In the same population, tea had no effect. A similar study of 45,869 men for 12 years demonstrated a similar effect for both caffeinated and decaffeinated coffees, which was significant at coffee intakes over 4 cups a day (-40% risk; Choi 2007).
Much of the protective effect of coffee against acute gout can be attributed to caffeine in the above studies; caffeine (1,3,7- trimethyl-xanthine) is a competitive inhibitor of xanthine oxidase (Kela 1980). The protective effect of decaffeinated coffee suggests other compounds may also important. For example, some evidence suggests that iron overload may contribute to the development of gout, and chlorogenic acids from coffee have been shown to reduce iron absorption (Mascitelli 2011). Conventional coffee, due to the roasting process, contains very little chlorogenic acids. However, recent innovations have lead to the availability of a green coffee extract high in chlorogenic acids, which can be taken in the form of a supplement. Green coffee extract supplements are a superior source of chlorogenic acids and other healthful coffee compounds as compared to conventionally roasted coffee beans used to make coffee beverages (Romero-Gonzalez 2009; Farah 2008).
An analysis of fiber intake data in 9,384 adults without cancer, diabetes or heart disease from the National Health and Nutrition Examination Survey (NHANES) 1999-2004 revealed a significant association between higher fiber intake and lower hyperuricemia risk. The study, which used a higher blood uric acid limit for the definition of hyperuricemia (8.4 mg/dL for men and 7.4 mg/dL for women), demonstrated a 55% reduction in hyperuricemia risk between the highest fiber consumption (9.5g fiber/1000 kcal of total food intake, or 19g fiber/day for the average 2000 kcal diet) and the lowest (<4.6 g/1000kcal; less than 9.2 g fiber/day) (Sun 2010). A smaller case-controlled study of 92 gout patients and 92 gout-free controls demonstrated a statistically significant reduction in the risk of gout amongst persons with the highest intake of total- and soluble fiber (Lyu 2003). While these mechanisms for this reduction is unknown, dietary fiber may inhibit purine or adenine absorption in the digestive system (Koguchi 2004). Fiber has also been shown to reduce other independent risk factors for gout, including hypertension (Streppel 2005; Whelton 2005) and high cholesterol (Brown 1999).
A small case-controlled study of 92 gout patients and 92 gout-free controls demonstrated a statistically significant reduction in the risk of gout amongst persons who consumed over 51.5 mcg/day of folate from food sources (a 70% reduction compared to those who consumed less than this value) (Lyu 2003). No significant effects on gout risk were observed for vitamins A, E, or the other B vitamins in this study.
Several Chinese medicinal plants have been tested for xanthine oxidase inhibitory activity. The most active was the methanol extract of Chinese cinnamon (Cinnamomum cassia), followed by Chrysanthemum indicum and Lycopus europaeus. Among water extracts, the strongest inhibition was observed with Polygonum cuspidatum, which is an excellent source of the polyphenol resveratrol (Kong 2000). These herbs have been used in China to suppress gout (Kong 2000). Extracts from two traditional Chinese anti-gout treatments (Paederia scandens and Smilax china) both decreased blood uric acid concentration in rats with experimentally-induced hyperuricemia (Yan 2008; Chen 2011).
Flavonoids may lower blood uric acid through their ability to inhibit the enzyme xanthine oxaidase; olive leaf constituents, milk thistle constituents, apigenin, myricetin, luteolin, and genistein have all shown this ability in laboratory experiments; apigenin had an inhibitory activity comparable to the synthetic xanthine oxidase inhibitor allopurinol (Pauff 2009; Lin 2002; Li 2011; Flemmig 2011). In fructose-induced hyperuricemic rodents, quercetin, rutin, kaempferol, myricetin, and puerarin all significantly reduced blood uric acid to levels equivalent to healthy control animals (Mo 2007; Hu 2009). Grape seed procyanidins were found to have uric acid-lowering effects in rats with hyperuricemia. The procyanidin-treated animals exhibited normal growth compared to animals treated with allopurinol, which exhibited some retarded growth (Wang 2004).
Anti-inflammatory Nutrients: A potential role in Chronic Gout?
While hyperuricemia and urate crystal formation are requirements for an acute gout attack and a contributing factor for chronic gout, inflammation is clearly central to the disease. Several labs have investigated the chemical cascades that mediate this process. Under certain conditions, cells of the innate immune system (the macrophages or "big-eaters") that reside within tissues recognize the presence of urate crystals. Through a process that is still not fully elucidated, these cells are stimulated to produce pro-inflammatory cytokines (particularly IL-1β), which recruit inflammatory white blood cells (neutrophils) to the site of crystal deposition (DiGiovine 1987; Dinarello 2010). The circumstances surrounding the cessation of inflammation in acute gout are equally puzzling. Data suggest a yet-unidentified gout promoting "factor" that must be present with the urate crystals in order for an acute attack to occur (Busso 2010).
Although it seems a reasonable assumption that anti-inflammatory nutrients may have a role in mitigating gout attacks, research in this specific area is lacking. The quick progression and resolution of acute gout may make it less amenable to nutrient "interventions" (many of which have only been tested for their long-term effects on inflammation). However, the intercritical periods between attacks have been associated with sustained low-level inflammation (Schumacher 2008), a situation more readily addressed by dietary modification. Nutrients that have been shown to attenuate joint inflammation and reduce pro-inflammatory cytokines (including IL-1β), such as curcumin (Moon 2010; Belcaro 2010), omega-3 fatty acids (Wann 2010), and resveratrol (Shakibaei 2008) may be especially suited for this purpose. Experimental diets high in the omega-3 fatty acid EPA and the healthy omega-6 fatty acid GLA were shown to reduce urate crystal-induced inflammation in a rat model (Tate 1988). Omega-3 supplements may be more suitable for hyperuricemic patients who are limiting fish intake (Choi 2010).