More than two-thirds of the body’s blood uric acid is endogenous, with food sources being only a small portion. However, given the reduced ability to excrete uric acid, the purine content of food is still a concern. Moreover, in the case of animal foods, high purine content in food means not only pressure on the body to excrete uric acid, but more often than not, it also means a poor dietary structure, which is an important factor leading to metabolic disorders. 1. What is “purine content”? First of all, it is important to know that purine is a component of the genetic material in the cell nucleus. Therefore, the more dense the cells are in biological tissues, the higher the purine content is. Foods that do not have a cellular structure, such as milk, have a very, very low purine content. There are also foods that are one big cell, such as various kinds of poultry eggs. No matter how big the egg is, it is only one cell, and one cell has only one set of genetic material, so the total amount of purines is very small. Fruits and vegetables are more “watery” in that they have a larger cell size and a large vesicle in them, and the amount of genetic material per unit weight is also very low. In contrast, foods that are dried, where the water has been removed and the ‘dry goods’ inside have been concentrated, generally have more purines. For example, dried beans appear to have a high purine content because it is so low in water. If you soak it in water, the water content increases several times, and then the purine content is reduced to a fraction of a percent. The same goes for mushrooms. Dried mushrooms seem to be particularly high, but if they are soaked, the content becomes a fraction or even a tenth all of a sudden. So, if you see a plant food with high purine content, don’t be afraid to check whether it is dried or fresh, or if it is aquafaba. In addition, tissues that are particularly ‘dense’ and have a very high metabolism will also contain higher levels of purines compared to tissues that have a low metabolic rate. For example, in the same animal, offal usually has a higher purine content than regular muscle, which in turn has a higher purine content than fatty meat. This is because fatty meat is fatty tissue with low metabolic activity, while offal usually has a higher metabolic rate, small, dense cells, and high levels of nuclear material. Fish roe is an egg cell that will keep dividing to form an embryo in the future, so it contains very high levels of purines. 2. How to classify the purine content of food? Medical books usually classify foods into four classes according to their purine content. When these foods are listed in a scattered way, people find it hard to remember and find the pattern. If we summarize them by food characteristics, it will be much easier to understand and remember. The first class is ultra-high purine foods, with purine content above 150 mg/100 g. Patients with gout and hyperuricemia should avoid these foods completely. They include various animal offal (liver, kidney, brain, spleen, etc.); some aquatic products (sardines, anchovies, fish roe, small shrimps, etc.); thick meat soups, thick fish soups, seafood hot pot soups and lamb hot pot soups, etc. The second class are medium to high purine foods, with purine content between 75 mg and 150 mg/100 g. Patients should have strict limits and should not consume them during acute attacks. They include various kinds of livestock meat (pig, cow, sheep, deer, etc.); poultry meat (chicken, duck, goose, pigeon, quail, turkey, etc.); some fish (bass, carp, crucian carp, eel, eel, etc.); crustaceans (oyster meat, shellfish, mussels, crabs, etc.), and dried beans (soybeans, black beans, mung beans, red beans, etc.). Here need special note is that other animal foods are 70 to 80% of water, while dry beans contain only 10% more water. It is unfair to compare foods with different water content. Considering that few people eat dry beans, they are boiled or even pureed with water before eating. But if the beans are soaked in water and then sorted, they will be relegated to the next rank among others. The third category is foods with low to medium purine content, with purine content between 30 mg and 75 mg/100 g. They include dark green tender leafy vegetables. They include dark green tender leafy vegetables (spinach and other leafy greens, asparagus and other tender stems); flowering vegetables (white cauliflower, broccoli, etc.); tender bean vegetables (mao beans, tender peas, tender fava beans); undried mushrooms (various fresh mushrooms); and some aquatic products (salmon, tuna, white fish, lobster, etc.). The fourth category is low purine content foods, which contain less than 30 mg/100 g of purine and require little concern about their purine content. They include milk (milk, cheese); various eggs (eggs, duck eggs, goose eggs, quail eggs, pigeon eggs, etc.); light-colored leafy vegetables (cabbage, cabbage, baby vegetables, etc.); root vegetables (potato, taro, sweet potato, radish, carrot, etc.); eggplant vegetables (tomato, eggplant, green pepper); melon vegetables (winter melon, loofah, cucumber, pumpkin, etc.); various fruits; various grains (rice, flour, millet, corn, etc.). white flour, millet, corn, etc.). Many people ask: I have hyperuricemia, can I eat green leafy vegetables with slightly higher purine content in the third category? Can I eat soy products? Can I eat mixed grains? Some doctors strictly forbid patients to eat grains on the grounds that they are higher in purines than refined white rice and pasta. However, if the overall health benefits are not considered and the only trade-off is the purine content, then it is absurd to conclude that “eating white sugar is better than eating millet” or “eating butter is better than eating tofu”. It is true that the purine content of white sugar is zero, but its nutritional value is also almost zero, and eating more of it will promote metabolic disorders. It is true that butter also has almost zero purine content, but eating more of it will promote obesity and hyperlipidemia. One epidemiological study specifically analyzed vegetables that are legendarily high in purines and did not find a correlation between them and gout risk or gout attacks. Also, no correlation was found between the intake of any whole grains, and gout and hyperuricemia. So, the answer given here is that for plant foods with an overall low purine content, even if the purine content is higher than that of white rice and white flour, it is worth eating them as long as they are good for weight, blood glucose and lipid control.