What is the relationship between gout and uric acid? How to prevent gout attacks?

Author: Wu Donghai, Chief Physician of China-Japan Friendship Hospital

Reviewer: Zhang Zhuoli, Chief Physician, Peking University First Hospital

When excessive uric acid is produced in the blood or its excretion is reduced, the balance of uric acid in the body will be broken, leading to an increase in uric acid.

Whether male or female, if the blood uric acid level is greater than 420 μmol/L measured twice on different days, it is diagnosed as hyperuricemia.

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There is a close relationship between gout and hyperuricemia, but high levels of uric acid do not necessarily lead to gout immediately. Usually, hyperuricemia needs to accumulate for a certain period of time before it causes gout, which takes an average of three to five years. In addition, if the patient has high uric acid, overeating, strenuous exercise, trauma, or infection can also induce gout.

1. Formation of uric acid

Uric acid has two main sources: one is exogenous intake, and the other is the body's own metabolic synthesis.

Exogenous intake mainly comes from food, which contains nucleotides, and nucleotides contain purine bases. After food enters the digestive tract, it is broken down, and purine bases are released, which are then converted into uric acid through a series of metabolic processes. Under normal diet conditions, uric acid from general food sources only accounts for a small portion of the total uric acid in the body, about 10%-20%.

Most uric acid comes from the body's own metabolism. The cells in the human body are constantly metabolizing and replacing the old with the new. When dead cells decompose in the body, they release purine bases, which are then metabolized to produce uric acid.

It is worth noting that the uric acid produced by the human body is no longer broken down and utilized, and is almost entirely excreted from the body. The excretion of uric acid is mainly through two channels:

There are about 1200mg of uric acid in the human body, and about 600-750mg is newly generated every day. About the same amount of uric acid is excreted every day to maintain dynamic balance. The kidney is the main organ for uric acid excretion, and 80% of the excreted uric acid is excreted from the body with urine; the remaining 20% ​​of uric acid is excreted with feces through the intestines and biliary system, part of which is excreted directly with feces, and the other part is further decomposed by microorganisms such as lactobacilli and bifidobacteria in the intestines, and its metabolites are eventually excreted with feces.

The production and excretion of uric acid are constantly changing in the human body, and the changing trends are influenced by genetic factors and environmental factors such as gender, age, diet, exercise, and medication.

2. The mechanism of gout

When the concentration of uric acid in the human blood is too high, the plasma cannot dissolve more uric acid, so some of the uric acid begins to precipitate and form crystals. The crystals continue to accumulate and finally form a thick crystal layer in the joints.

These precipitated urate crystals will be recognized as foreign bodies by immune cells (such as white blood cells), which will then engulf the urate crystals and release inflammatory factors (such as IL-1) and hydrolases, leading to cell necrosis and the release of more inflammatory factors, causing an inflammatory response. Eventually, the joints will become red, swollen, hot, and painful, which is an acute attack of gout.

In general, gout is caused by excessive uric acid, which forms urate crystals. The crystals are deposited in the joints, causing a series of inflammatory reactions.

The foot, particularly the big toe, is most commonly affected by acute gout attacks, primarily because of the relatively low temperature and susceptibility to trauma in this area, where even minor injuries may result in changes in the local acid-base balance.

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Gout tends to attack at night. Some theories believe that drinking very little water during sleep at night may lead to mild dehydration, which increases the uric acid concentration. At the same time, normal people experience alkaline tides in the morning and after lunch, which raises the pH to above 6.0. The alkaline tide in gout patients weakens or disappears, especially at night, which lowers the pH value, that is, increases the acidity of the blood. For patients with high uric acid levels, their blood itself is acidic, and the solubility of uric acid decreases in an acidic environment, thereby increasing the risk of urate precipitation. Therefore, most gout attacks occur at night.

3. Causes of gout attacks

The prerequisite for a gout attack is the presence of hyperuricemia, and in addition to this, there are many other inducing factors.

First, overeating is one of the important causes. Since most of the exogenous purines ingested from food are not used by the body for nucleic acid synthesis, but are broken down and converted into uric acid, consuming a large amount of high-purine food in a short period of time will significantly increase the blood uric acid level. For patients who already have hyperuricemia, this can easily induce gout attacks or aggravate symptoms.

Secondly, dehydration or lack of water intake is also a key cause. Dehydration or reduced water intake will lead to a decrease in blood volume, which in turn increases the uric acid concentration and increases the risk of urate precipitation and deposition. In addition, changes in ambient temperature and body fluid pH will also affect the solubility of uric acid. Specifically, a decrease in temperature will reduce the solubility of uric acid, and in an acidic environment, the solubility of uric acid will become even lower, making it easier to deposit.

Finally, the use of certain drugs can also affect uric acid excretion, leading to increased uric acid, thereby inducing gout attacks. For example, the use of aspirin, diuretics, anti-tuberculosis drugs and cyclosporine can all become triggers for gout attacks.

4. Prevent gout attacks

To prevent gout, you must first lower your blood uric acid and avoid the triggers of gout. If your uric acid level is too high, you can use uric acid-lowering drugs under the guidance of a doctor. In addition, you must make adjustments to your life and change your lifestyle.

First of all, don't overeat and control your diet appropriately in any occasion.

Second, eat less or no high-purine foods, such as animal offal, seafood, beef and mutton, etc. These foods may increase the level of uric acid in the blood. Although some plant foods also contain high purines, such as lentils and tofu, plant purines are less harmful than animal purines and can be eaten appropriately. On the contrary, the intake of vegetables, fruits and grains should be increased to supplement the nutrients needed by the body. If you are worried about insufficient protein intake, you can choose milk and eggs as high-quality protein sources.

Third, drinking should be avoided, especially beer should be completely avoided, followed by white wine. If there is a real need, red wine can be tasted in moderation.

Fourth, avoid drinking sugary drinks, especially those with high fructose content, as fructose can affect the metabolism of uric acid and induce gout. It is recommended to drink tea and boiled water. Drinking more water can help dilute uric acid and avoid crystallization due to excessive uric acid concentration.

Fifth, reduce the intake of drugs that affect uric acid excretion, such as aspirin, diuretics, anti-tuberculosis drugs and cyclosporine.

Sixth, obese people generally have higher uric acid levels, and they are also prone to problems such as high blood sugar, high blood lipids, and high blood pressure. Therefore, actively and healthily losing weight is very beneficial for improving these problems.