Is gout caused by excessive intake of purine? The truth is different from what you think!

Gout is a "nightmare" for many people. When it attacks, the pain is as sharp as a knife and unbearable. It can be said that "the pain is excruciating and comes and goes like the wind."

Gout was once one of the oldest diseases prevalent in the West, but it is now also prevalent in my country. According to the 2018 data on chronic diseases and risk factors in my country, the prevalence of hyperuricemia among adult residents reached 14.0% (24.5% for males and 3.6% for females), of which the prevalence among young males (18-29 years old) reached 32.3%, showing a significant trend of getting younger. [1] A study published in 2019 showed that the prevalence of gout in my country ranged from 0.03% to 10.47%, and was increasing year by year. [2]

When it comes to gout, we can't leave out "purine". Even many people will stare at the purine content table when eating, and dare not eat foods with high purine content, for fear that they will suffer from gout. In fact, there is no need to do so. In this article, we will talk about the relationship between purine and gout, so that you can eat and drink with confidence.

1. High uric acid ≠ gout

Many people think they have gout simply because their physical examination shows high uric acid levels. In fact, this is not the case. There is a long way to gout. Gout is only diagnosed when hyperuricemia causes acute arthritis, tophi, and changes in joints and kidneys. [3]

Having hyperuricemia does not necessarily mean that you will develop gout. Generally speaking, about 10% of people with hyperuricemia will develop gout.

2. Where does purine come from?

Purine mainly comes from our own synthesis, and a small amount of purine is also ingested through diet.

Proteins and nucleic acids are the basis of all life. Nucleic acids include DNA and RNA. Purines are the products of further metabolism of DNA and RNA, including adenine, guanine, hypoxanthine and xanthine. Xanthine is the main source of uric acid. [3]

Almost all foods contain purine, such as meat, eggs, milk, beans, vegetables, fruits, etc. The purine in food will be absorbed through the gastrointestinal tract and enter the liver, and will be further metabolized into uric acid.

3. Is gout caused by consuming too much purine?

The metabolic product of purine is uric acid, so most people believe that hyperuricemia is caused by eating foods high in purine.

Not really. The truth is different from what you think.

Let’s first talk about the source of uric acid. There are two main sources of uric acid in the human body, including endogenous and exogenous. About 80% of the uric acid in our body comes from the metabolism of endogenous purines, and only 20% of uric acid comes from foods rich in purines in the diet, which is exogenous. As for the excretion of uric acid, it is mainly carried out through the kidneys. In a normal person, about 70% is excreted by the kidneys and 30% is excreted by the intestines every day. [3]

Therefore, increased purine anabolism and reduced uric acid excretion will increase serum uric acid levels and induce hyperuricemia or gout. The most common cause is problems with kidney metabolism of uric acid. Some people also have enzyme deficiencies caused by gene mutations, which may also lead to increased blood uric acid levels.

In other words, endogenous metabolic disorders are the primary factor leading to hyperuricemia, and the high-purine diet that everyone is concerned about is not the main factor inducing gout. Some studies have also further confirmed that diet is not the main factor.

A study published in the British Medical Journal in 2018 [4] included a total of 16,760 individuals of European descent from the United States (8,414 men and 8,346 women) for analysis. All individuals were over 18 years old, had no kidney disease or gout, and were not taking urate-lowering or diuretic medications.

A total of 63 kinds of food were involved in the study. After adjusting for various factors, it was found that beer and liquor had the greatest impact on blood uric acid concentration. On average, every additional 350 ml of food consumed per week would increase blood uric acid concentration by 1.38 μmol/L, but it could only cause a 0.99% change in blood uric acid levels. Even if all 63 kinds of food were added together, it could only cause a 4.29% change in blood uric acid levels. According to estimates based on whole genome data, genes affect 23.9% of blood uric acid changes in men and 40.3% in women.

In addition to this study on white Americans, there was also a small cross-sectional study involving 266 adults in Taiwan, China, which found that there was no significant relationship between dietary patterns and uric acid in healthy people. [5]

Therefore, compared with genes, diet has little impact on blood uric acid levels, and healthy people do not need to deliberately avoid foods with high purine content.

4. Who is prone to hyperuricemia?

-Genetic factors: Among patients with primary gout, 10% to 52% have a family history of the disease, and 15% to 25% of close relatives of gout patients suffer from hyperuricemia. [6]

- Influence of chronic diseases: People who are obese, have diabetes, or have hyperlipidemia are more likely to suffer from gout. Some studies have mentioned that this may be because obese people have endocrine disorders, and the levels of androgens and adrenocorticotropic hormones decrease, which inhibits the excretion of uric acid. The risk of gout in people with type 2 diabetes is 4.4 times that of non-diabetic people. [6]

-Menopause: Estrogen promotes uric acid excretion. Compared with premenopausal women, postmenopausal women are more likely to suffer from gout due to decreased estrogen secretion.

- Long-term heavy drinking: Alcohol itself contains purine, which increases the production of uric acid, and the metabolite of ethanol, lactic acid, inhibits the excretion of uric acid. Therefore, people who drink a lot of alcohol for a long time will have problems with uric acid excretion, which is manifested as excessive uric acid production and reduced uric acid excretion.

The purine content of different types of wine varies, generally in the order of aged wine > beer > ordinary rice wine > white wine. [6]

5. What should I do if I already have hyperuricemia?

Although diet has little effect on blood uric acid levels in healthy people, a high-purine diet can be a contributing factor to the development of gout in people with a predisposition to it. [3] Therefore, potential gout patients and those who already have hyperuricemia need to pay attention to their diet.

-Choose the right food: There is no need to strictly control your diet. Just eat according to the recommendations of the Dietary Guidelines for Chinese Residents.

If you are in the acute stage of gout, choose low-purine foods, such as milk, eggs, refined grains, fresh vegetables, etc., do not drink alcohol, and avoid all meat. People with chronic gout should try to avoid high-purine foods on the basis of a normal diet.

Most fruits and vegetables, cereals, milk, eggs, and nuts are low-purine foods; dried beans and dried fungi and algae have higher purine content.

- Be wary of high-fructose foods: Foods high in fructose increase the production of uric acid [3]. Try to avoid sweetened drinks and foods that include fructose, high-fructose corn syrup, and honey in their ingredients. Also eat less high-fructose fruits, such as lychees, bananas, apples, watermelons, grapes, and kiwis.

- Regular meals: Overeating and eating too much meat in one meal can easily induce gout. It is important to have regular meals and avoid excessive hunger. You can also eat small meals frequently.

-Cooking suggestions: When making meat dishes, it is best to cook the meat in advance and discard the soup before cooking. This can reduce the purine content in the food.

As for condiments, such as chili, pepper, Sichuan pepper, ginger, mustard, etc., it is best to use less or no condiments, as they can excite the nerves and may induce gout.

- Adopting the DASH diet: A study involving 44,444 Americans followed for 26 years found that the DASH diet can reduce blood uric acid levels in patients with hyperuricemia and reduce the risk of gout attacks. [6]

- Drink enough water: Drinking enough water is conducive to the excretion of uric acid and the prevention of uric acid kidney stones. People with high uric acid should drink 2000ml of water every day. If accompanied by kidney stones, it is best to drink 3000ml.

In addition, if you sweat a lot during exercise, you should also pay attention to replenishing water. Because exercise will increase lactic acid in the body and affect the excretion of uric acid, you should pay attention to replenishing boiled water or weak alkaline water, and avoid strenuous exercise.

Summarize:

Gout cannot be entirely attributed to excessive intake of purine. Normal and healthy people do not need to deliberately avoid foods high in purine. They just need to follow the dietary guidelines to eat a balanced diet. However, for people with a family history of genetic diseases or those who already have hyperuricemia, they should be appropriately wary of high-purine foods.

References:

[1] Xu Dong, Zhu Xiaoxia, Zou Hejian, et al. Gout diagnosis and treatment guidelines[J]. Chinese Journal of Internal Medicine, 2023, 62(9): 1068-1076. DOI: 10.3760/cma.j.cn112138-20221027-00796

[2] None, Liu Wei. Guidelines for the diagnosis and treatment of gout and hyperuricemia using integrated traditional Chinese and western medicine[J]. Journal of Traditional Chinese Medicine, 2023, 64(1): 98-106

[3] Gu Jingfan, Du Shouyin, Guo Changjiang. Modern Clinical Nutrition. Science Press. 2009. 2nd edition

[4]Major, Tanya J et al. "Evaluation of the diet wide contribution to serum urate levels: meta-analysis of population based cohorts." BMJ (Clinical research ed.) vol. 363 k3951. 10 Oct. 2018, doi:10.1136/bmj.k3951

[5]Tsai, Yi-Tsen et al. “Relationship between dietary patterns and serum uric acid concentrations among ethnic Chinese adults in Taiwan.” Asia Pacific journal of clinical nutrition vol. 21,2 (2012): 263-70.

[6] Yang Yuexin, Ge Keyou. Chinese Nutrition Science Encyclopedia 2nd Edition (Volume 2)[M]. People's Medical Publishing House, 2019

[7] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 2[M]. Peking University Medical Press, 2019

The article is produced by Science Popularization China-Creation Cultivation Program. Please indicate the source when reprinting.

Author: Xue Qingxin, member of Chinese Nutrition Society, registered dietitian, health manager, public nutritionist

Reviewer: Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center