Gout & High Uric Acid
GOUT & HIGH URIC ACID
Dietary Approaches to Control Hyperuricemia and Reduce Gout Risk
Gout is a form of arthritis in which excess uric acid forms crystals in joints and other tissues causing painful inflammation. Gout attacks cause a characteristic painful inflammation of one or more joints of the extremities. An acute attack of gout, although brief and usually subsiding spontaneously, can be debilitating.
The disease appears to favor men over women by almost 3:1 (Zhu 2011). Also, there appears to be a significant 44% increase in gout frequency from previous estimates just a decade earlier (Kramer 2002).
The primary risk factor for gout is elevated levels of a metabolic by-product called uric acid in the blood; this condition is known as hyperuricemia. Hyperuricemia is estimated to affect over 21% of the US population, and doubles in frequency between ages 20 and 80 years (Zhu 2011).
Hyperuricemia increases the risk of not only gout, but other diseases as well, including hypertension, kidney disease, and metabolic syndrome. Even during the asymptomatic periods between gout attacks, the body is exposed to periods of low-grade, chronic inflammation.
Uric Acid Metabolism
Uric acid is the final product of purine metabolism in humans. Purines are components of nucleosides, the building blocks of DNA and RNA. Purine nucleosides (adenosine and guanine) are used in the creation of other metabolically important factors as well, such as adensosine triphosphate (ATP; the energy-carrying molecule), S-adenosyl-methione (SAMe; the methyl donor), and nicotine adenine dinucleotide (NADH; an important cofactor in energy production and antioxidation). Humans have developed robust systems for synthesizing sufficient purine nucleosides for their metabolism using readily available materials (such as glucose, glycine, and glutamine), as well as recycling purine nucleosides throughout the body or from the diet.
Excess purine nucleosides are removed from the body by breakdown in the liver and excretion from the kidneys. For most mammals, the purines are first converted into the intermediate uric acid, which is then metabolized by the enzyme uricase into the compound allantoin. Allantoin is a very soluble compound that can easily travel through the bloodstream, become filtered by the kidneys, and be excreted from the body. In contrast to other mammals, humans lack a functional uricase enzyme, and can only break purines down into uric acid.
The levels of uric acid in the blood depend on two factors:
- Rate of uric acid synthesis in liver – Since uric acid results from purine degradation, its levels are influenced by both the amount of purines synthesized in the body, as well as the amounts of purines absorbed from the diet (Richette 2010).
- Rate of uric acid excretion from kidneys – Excretion has the greatest effect on blood uric acid levels, with about 90% of hyperuricemia cases attributed to impaired renal excretion (Choi 2005). Impaired excretion is most often due to abnormalities in the kidney urate transporter (called URAT1) or organic ion transporter (OAT), both of which control the movement of uric acid out of proximal kidney tubules and into urine (Enomoto 2002).
One intriguing aspect of uric acid is that although it appears to be a "waste product" of purine metabolism, only about 10% of the uric acid is excreted from the body (Richette 2010). In other words, rather than eliminating uric acid, a healthy kidney returns up to 90% of it to the blood stream. The reason for this is likely due to the role of uric acid as one of the most important antioxidants in body fluids, responsible for the neutralization of over 50% of the free radicals in the blood stream (Glantzounis 2005).
Uric acid has a principle role in protecting high-oxygen tissues (like the brain) from damage, and low blood uric acid levels have been associated with the progression or increased risk of several neurological disorders, including Amyotrophic Lateral Sclerosis (Keizmann 2009), Multiple sclerosis (Rentzos 2006), and Huntington's (Auinger 2010), Parkinson's (Andreadou 2009), and Alzheimer's diseases (Kim 2006).
Hyperuricemia and the Development of Gout
Uric acid is a metabolic "waste product" with poor solubility in body fluids, yet its potential role as a primary antioxidant in body fluids suggests that it should be kept at sufficient levels in the blood. Commonly, the upper limit of this range is taken as 8.6 mg/dl in men and 7.1 mg/dl in women, (although some laboratories and research groups use different limits) (Zhang 2006a; Sclesinger 2009; Sun 2010). Uric acid levels above this limit are considered as hyperuricemia.
Hyperuricemia is a primary risk factor for the development of gout, although it is likely that many hyperuricemic individuals will not develop symptoms. (Alvarez-Lario and Macarrón-Vicente 2011). While the risk of a gout attack increases with blood uric acid, the annual occurrence of inflammatory gout is fairly low.
Hyperuricemia without symptoms (asymptomatic hyperuricemia) is also a risk factor for other diseases (see below). Although patients with asymptomatic hyperuricemia may never experience the symptoms of a gout attack, ultrasound studies have revealed that up to one-third may have urate deposits and evidence of inflammation in their joints and surrounding soft tissues (Puig 2008).
As local serum uric acid concentrations rise above their limit of solubility, monosodium urate can form needle-like crystals in cartilage and fibrous tissues. Here, the crystals may reside for years without causing problems (Doherty 2009). Urate crystals within tissues have two fates: they can re-dissolve in body fluids and re-enter circulation, or may be "shed" from the tissue. Shed monosodium urate crystals can enter nearby joint spaces, where they are quickly engulfed by immune cells. This activates a localized inflammatory response, leading to the characteristic arthritis of gout (Martinon 2006).
An attack of acute gout usually appears as a sudden inflammatory arthritis of a single joint in the lower extremities, most often the joint of the big toe. Other joints that are frequently affected include the mid-foot, ankle, knee, wrists and finger joints. The skin may be red and shiny above the affected area. Attacks often begin in the early morning and reach a peak within 6 to 24 hours. The pain is severe, and patients often cannot wear socks or touch bedsheets during flare-ups (Eggebeen 2007). Even without treatment, the attacks typically subside spontaneously within several days to two weeks.
Gout attacks can be triggered by a variety of factors, many of which reduce the solubility of urate in the blood; these include infection, trauma to the joint, rapid weight loss, dehydration, acidosis, and lower body temperature (which explains the timing of gout attacks and why they most frequently occur in the extremities) (Eggebeen 2007).
Recurrent attacks of acute gout often lead to chronic tophaceous gout, in which monosodium urate deposits (tophi) form in the soft tissues, usually along the rim of the ear, over the elbow joint, and in the joints of the fingers and toes. Tophi reduce the growth and viability of bone cells (osteoblasts) (Chhana 2011) and if left untreated, tophaceous gout can lead to significant joint erosion and loss of function (Eggebeen 2007).
The Role of Hyperuricemia in Other Conditions
Although hyperuricemia is most often associated with gout, elevated blood levels of uric acid have also been associated with other diseases. Hyperuricemia and gout are both risk factors for kidney or bladder stones (urolithiasis). Both conditions increase the risk of forming not only uric acid stones, but also the more common calcium oxalate stones. The presence of calcium oxalate stones is 10-30 times higher in gout patients than those without gout (Pak 2005). Deposits of monosodium urate crystals in kidney tissues can result in kidney damage (nephropathy), either acutely by formation of crystals within the tubules of the kidney, or through a chronic inflammatory response to urate deposits in other tissues of the kidney (Johnson 1999).
Hyperuricemia is a risk factor for cardiovascular diseases in high risk groups, and has been associated with small increases in the risk of coronary events (Kim 2009), heart failure (Ekundayo 2010), and stroke (Kim 2010).
Hyperuricemia is an integral part of metabolic syndrome (Doherty 2009), and epidemiological studies have demonstrated that elevated uric acid levels substantially increase metabolic syndrome risk (and vice versa) (Dao 2010 ; Choi 2007a). Hyperuricemia was associated with increased risk of type 2 diabetes, and that male patients with gout had a 41% increased risk for the disease (Choi 2008).
Several risk factors promote a high uric acid level and gout attacks:
- Increasing age and being male
- Intake of high-purine foods, including red meat (beef, lamb, pork), seafood
- Alcoholic beverage intake, specifically beer and spirits
- Some medications (e.g. loop and thiazide diuretics, but also antituberculous drugs, cyclosporin, and levodopa)
Diseases Associated with Gout/High Uric Acid:
- Heart disease
- Heart failure
- Metabolic syndrome and type 2 diabetes
- Kidney stones or other kidney disease
- Early menopause
NUTRITIONAL APPROACHES TO CONTROL HYPERURICEMIA & REDUCE GOUT RISKS
Lifestyle and Dietary Changes
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 as excess adiposity is associated with increased uric acid levels.
- 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.
- 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. 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.
Nutrients that may help 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 concentrations (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. 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.
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).
Terminalia bellerica (T. bellerica), native to parts of Asia, is an important medicinal plant in traditional Ayurvedic medicine. The dried fruit of T. bellerica is the part used in medicine, and is considered to have a wide range of benefits including cholesterol- and blood sugar-lowering effects; protecting the heart, kidney, and liver; and combatting inflammation and oxidative stress (Kumar 2014; Motamarri 2012).
T. bellerica is a source of many bioactive compounds that contribute to its usefulness in gout and arthritis. Specifically, T. bellerica is believed to inhibit the enzyme xanthine oxidase, which may account for its ability to lower uric acid in both animals and humans. In fact, in a laboratory trial, T. bellerica was found to exert the same degree of xanthine oxidase inhibition as the gout drug allopurinol (Usharani 2016; Cock 2015; Motamarri 2012).
A six-month, double-blind, placebo-controlled clinical trial was completed by 88 individuals with elevated uric acid. This trial compared 500 mg twice daily of a T. bellerica fruit extract, standardized to 15% tannins, to 250 mg of the same extract, placebo, and 40 mg of the uric acid-lowering medication febuxostat. The higher dosage of T. bellerica reduced uric acid concentrations by over 27%, while the low dose was roughly half as effective; and uric acid increased in the placebo group. While all subjects in the febuxostat group reached the target uric acid concentration of ≤ 6 mg/dL, nearly 89% in the high dosage and 12% in the low-dosage T. bellerica group did so as well. No adverse effects were observed in any subjects receiving T. bellerica (Usharani 2016).
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).
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).
- Vitamin C: 1000 – 2000 mg daily
- Cherry extract: 1000 – 3000 mg daily
- Green Coffee extract (standardized to 50% chlorogenic acid): 400 – 1200 mg daily
- L-Methylfolate: 1000 mcg daily
- Quercetin: 250 – 500 mg daily
- Grape Seed; standardized extract: 100 – 200 mg daily
- Olive leaf; standardized extract: 500 – 1000 mg daily
- Milk thistle; standardized extract: 750 mg daily
- Fiber: 30 – 40 g of fiber daily from food and supplemental sources
- Fish oil (with olive polyphenols): 1400 mg EPA and 1000 mg DHA daily
- Curcumin (as highly absorbed BCM-95®): 400 – 800 mg daily
- Trans-Resveratrol: 250 – 500 mg daily
- Terminalia bellerica extract (std. to 15% tannins): 1000 mg daily
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