Urine alkalization facilitates uric acid excretion

Written by: Ana Iturbides, Health Writer, Acupuncture Atlanta

Aya Kanbara, Masayuki Hakoda, Issei Seyama

Background
Hypouricemia is a primary concern of Kanbara and colleagues. This occurs when there is a deficiency of uric acid in the blood and has been associated with the onset of gout, incidence of cardiovascular disease, renal disease, hypertension, and diabetes (Kenbara et al., 3). Most current medical interventions that are widely used for the treatment of gout have relied on pharmacological methods. One common pharmacological tool is a xanthine oxidase inhibitor, which is a variety of antidepressant (MedLine Medical Dictionary). These methods, while often effective, also carry the risk of side effects. The authors believe that dietary interventions may be viable alternatives for the treatment of hypouricemia.
Kanbara and colleagues cite two prominent studies to provide background for their hypothesis: the first was conducted by Hagos, Stein, Ugele, Burckhardt, and Bahn and the other was conducted by Guggino, Martin, and Aronson. These studies focused on the mechanisms of uric acid re-absorption and transport in the body. Uric acid is a weak acid that is present in small amounts in human urine as an end product of purine metabolism. Both of these studies have hypothesized that the commitment of human organic acid transporter 4 can carry out inwardly directed urate transport in exchange with outwardly directed OH movement (Kanbara et al., 4). Kanbara and colleagues take this hypothesis into account as they study the how urine pH is determined by acid generation from food metabolism. This article seeks to show that designed diets are effective in removing uric acid from the body and hope to show that alkaline urine is more favorable for removal than acid urine.

Methods
Subjects consisted of 26 healthy, university age women who did not report any health problems. The subjects were given diets that corresponded with data provided by the Japanese Health, Welfare, and Labor Department. Every participant was given both diets and each diet occurred in a separate period. Each diet period lasted for 5 days; diets were analyzed for protein, energy, purine, and amino acid content. During each diet period, different recipes were made using the same compositions of natural food materials suggested by government data.
There were two general diet categories: alkali and acid. The acid diet was rich in protein and contained less fruits and vegetables. The alkali diet contained less protein but was rich in fruits and vegetables. The alkali diet contained 2212 kcal/d of energy and 60 g/d of protein. The acid diet contained 2222 kcal/d of energy and 120 g/d of protein (Kanbara et al., 12). Clearly, the diets are very similar in energy content and very different in protein content. Urine samples were collected once every 24 hours and stored in a refrigerator. Baseline urine samples were collected before subjects were given the diets and were analyzed for volume, pH, titration acid, organic acid and creatinine.

Analysis
According to a study by Lennon, Lemann, and Litzow, the production of endogenous acid is determined by the sum of three parts. These parts consist of the oxidation of sulfate, the endogenous formation of un-metabolized organic acids, and the net gastrointestinal absorption of alkali, which is produced by the oxidation of organic cations and anions. Kanaba and colleagues used this simplified method to calculate the production of endogenous acid (Kanbara et al., 6). Other tools used for analysis include a Hitachi HPLC unit that was used to calculate bicarbonate concentration, urine pH, and organic acid salt concentration. Other tests to measure creatinine were determined using a test called the Folin method.
Statistical analysis was done by separating first and second diet periods. Two group samples were tested independently and were presented as a mean +/- standard deviation. These data were used in a T test to measure significance of changes in measured parameters between the acid and alkali periods.

Results
Change in urine pH and creatinine excretion was the first of three observations that the authors emphasized in the study. Creatinine is a crystalline compound that is made of creatine (MedLine Medical Dictionary). They noted that it took three days to achieve a steady level of urine pH. It was also noted that, during all experimental days, the total amount of creatinine excretion remained unchanged since it is widely known that creatinine concentration in the serum of young people with no major health problems seems to remain constant (Kanbara et al., 8).
The second observation that the authors emphasized is the relationship between acid generation in the body and acid excretion in urine. The authors found a significant difference in sulfate (SO4) levels between the periods of acid diets and the periods of alkali diets. This is because the amount of sulfar-containing amino acid in the acid diet far surpasses that of the alkali diet. The authors also noted that the values of urinary ammonium, phosphate, and sulfate were lower in the alkali diet than they were in the acid diet (Kanbara et al., 8).
The last observation emphasized in the study was the effect of change in urine pH on the uric acid excretion. The amount of excreted uric acid increased with an increase in luminal pH (Kanbara et al., 9).

Discussion and Conclusion
The authors summarize their results as follows: as urine pH increased by suppressing metabolic degradation of food materials, uric acid excretion increased significantly. This finding is significant because purine content in the alkaline diet was found to be less than in the acid diet, which suggests that the excretion of uric acid is suppressed in acidic medium. The authors claim that this provides a very important explanation into a widely held view that gout is most common among people whose diet is rich in meat and low in fruits and vegetables (Kanbara et al., 9). Sulfur-containing amino acids are a main component of urine acidity and are abundant in animal proteins, which means that people who consume large amounts of animal protein relative to fruit and vegetable consumption will excrete more uric acid. This will ultimately lead to difficulty in removing uric acid from the body, which puts the person who consumes a diet rich in meat at increased susceptibility for gout than a person who consumes more vegetables.
The authors conclude by summarizing the relationship between alkalization of urine by the manipulation of food materials and the promotion of uric acid (Kanbara et al., 10). They show that, through the construction of a nutritionally balanced menu that emphasizes the abundance of fruits and vegetables, dietary intervention can be a suitable prevention method for Hypouricemia.

References
[1] Kanbara, A., Hakoda, M., and Seyama, I. “Urine alkalization facilitates uric acid excretion”. Nutrition Journal 9(2010).
[2] MedLine Medical Dictionary. http://www.nlm.nih.gov/medlineplus/mplusdictionary.html.

This article was published on 12/23/2010 13:49.

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