Purines and Purine-Rich Foods

The Purines

Purines are a group of nitrogenous organic substances found in all living cells . The best known purines, as nitrogenous bases of DNA and RNA , are adenine and guanine; these substances share with the other exponents of the family a molecular structure with two condensed nitrogenous heterocyclic rings (because they derive from purine, where a condensed penta-atomic ring is recognized with a hexa-atomic ring). Among the other most significant purines we mention caffeine , theobromine and uric acid.

Purine excess

The human organism continuously synthesizes the purines necessary for the synthesis of new nucleic acids ; to this endogenous biosynthesis , which occurs mainly in the liver , is then added the food intake; in addition, there are pathways for recovery, interconversion (formation of one purine from another) and degradation of excess purines.

Uric acid or urate is the main catabolite resulting from the degradation of purines.

Alterations of Purine Metabolism and Hyperuricemia

Some individuals have congenital deficiencies of enzymes involved in the purine interconversion, recovery, and degradation pathways. These and other disturbances in purine metabolism and uric acid excretion can cause hyperuricemia (excess uric acid in the blood) or hypouricemia (deficiency of uric acid in the blood).

Hyperuricemia is a fairly common condition characterized by excess uric acid in the blood . Hyperuricemia can trigger an arthritic condition called gout, characterized by an increase of uric acid in body fluids; this excess leads to the formation and precipitation of uric acid crystals within the joints , triggering gouty attacks (severe painful joint inflammation , with local redness and swelling). Apart from the joints, the most common storage areas for excess uric acid are the kidneys (up to renal failure ) and the skinof the ears, hands and elbows (where so-called tophi are formed , palpable masses visible under the skin).

Many of those with hyperuricemia have an inherited tendency to produce large quantities of uric acid, while gout is rarely caused by the consumption of purine-rich foods alone in the absence of a genetic predisposition. This does not mean that in the case of gout and hyperuricemia it is still important:

• limit the consumption of foods rich in purines;
• follow a sober diet (gout was once defined as the “disease of the rich” as it was typically associated with food excesses);
• drink plenty of liquids, at least 2/3 liters a day, especially if it’s hot (dehydration raises the risk of gouty attacks); plenty of water can prevent kidney stones to which gouty people are particularly exposed; herbal infusions can be a good solution to increase fluid consumption, moreover, some diuretic herbal teas can favor the excretion of excess uric acid;
• try to reduce body weight , if excess, while avoiding excessively restrictive diets; overweight people , especially if with fat concentrated in the abdomen , are more exposed to the risk of gout;
• limit or eliminate alcohol consumption ; beer is particularly inadvisable because it has a high purine content compared to wine and other spirits ;
• avoid fructose as a sweetener , as it increases uric acid retention ;
• prefer sources of complex carbohydrates and reduce foods high in fat ;
• also pay attention to aspirin , which limits the filtration of uric acid at the renal level ; better to prefer the paracetamol .

Purine-rich foods

• Foods most likely to trigger gout contain 150 to 1,000 milligrams of purines for every 100 grams. They include high protein animal products such as anchovies, brains, consommé, gravy, herring , offal , meat extracts , minced meat, mussels and sardines.
• Other foods that can contribute to gout contain small amounts of purines (50 to 150 milligrams per 100 grams). In severe cases it is necessary to limit these foods to no more than one serving per day; this food class includes asparagus , dried beans , cauliflower , lentils , mushrooms, flour , oats , dried peas, oysters , spinach , cereals , fish , meat and poultry. Limit them to 90 grams five times a week.