What Are Purines?
Purines include adenine, guanine, hypoxanthine, xanthine, and caffeine. The first four purines, in combination with pyramidines, make up the genetic codes DNA and RNA, and energy molecules, such as ATP, GTP and coenzyme A. They are essential for life and are found in all plant and animal cells.
How Purine Rich Diet Causes Gout
Purine metabolism, to be specific their break-down, in the liver, produces uric acid. Uric acid is an antioxidant and has beneficial effects, such as as a free-radical scavenger. When it accumulates to a high level in the blood, however, it can cause gout and other health problems.
Gout is a form of arthritis caused due to accumulation of uric acid crystals in joints, especially in the big toe.
A 12-year study that followed eating habits and gout incidence in a large number of men found that eating food rich in purine, such as meat and seafood, was associated with high risk of gout. Whereas higher level of consumption of dairy products, especially skimmed types, was associated with a reduced risk of gout. Moderate intake of purine-rich vegetables or protein was not associated with an elevated risk of gout. A recent study also found a positive association between fractose, a type of sugar, and sweetened beverages and gout.
According to some studies, a purine-free diet decreases blood uric acid level, on average, from 1.0 to 1.2 mg/100 ml; whereas, consumption of 4 g of ribonucleic acid (RNA), purine, per day, increases blood uric acid level from 1.5 to 2.0 mg /100 ml.
Recommended Daily Intake of Purines
The Dietary Guidelines for Americans has no recommended daily intake for purines. In Japan, to prevent an abnormal high level of uric acid in blood and gout, it is recommended to keep purine consumption to under 400mg per day.
Foods High or Low in Purines
In the following tables are estimates of total purine content in a variety of food items, presented in descending order. Total purine content is based on the sum of all the four purine bases. Meat and meat products have high total purine content, where as cereal foods contain low purine content. Generally, there is a positive association between protein and purine content in diet.
Table 1: High or low purine food sources.
|Food Sources of Purine||
Total purine content
|lamb, roasted, chop||127.5|
|Pork, roasted, chop||119.0|
|Fish, white, fresh||115.9|
Purine content also varies depending on the part of the meat or organ type.
Table 2: Purine content in chicken, pork, lamb, and beef parts.
|Purine sources||Total purine content
|Chicken organs and parts|
|Pork, beef, and lamb organs
According to a study that compared free and total purine bases content in meat products (steak, beef liver and haddock fillets) before and after cooking, cooking appears to increase the level of free and total purine bases in a diet.
Table 3: Total purine content in raw and cooked foods.
|Meat products||Total purine content