For a long time, purine-rich foods have been blamed to increase uric acid levels and increase the likelihood of gout attacks. However, nutritional studies in the last decade have shown that some purine-rich foods like legumes can be protective; while other previously unknown factors like fructose have been identified as detrimental. Read on and find out.
Gout is characterised by an excessive build up of uric acid (UA) in the blood that leads to the formation of crystal deposits around the joints. This condition not only causes intense pain and inflammation of the joints, but in the long term it can increase the likelihood of suffering from more serious conditions such as cardiovascular disease and diabetes. Making intelligent dietary choices can effectively lower UA levels and decrease the likelihood of suffering from gout. Generally, people at risk of suffering from this condition are advised to lower their consumption of purine-rich foods; since purines are broken down into UA by the body. This is generally a good starting point, but it is worth understanding that there are foods that break this rule and should be included in an anti-gout diet.
Figure 1. Individuals that suffer constant gout attacks normally have higher than normal UA levels in the blood and eating high purine foods e.g. red meat (a) will elevate them further. This is because the dietary purines are eventually broken down into UA; increasing the UA pool (b) in the body. (c) Furthermore, people with impaired kidney function may be unable to filter out the excess UA from the blood; favouring its accumulation in the tissues where crystals can form around the joints (d).
A common misconception that people have is to think of protein-rich foods as bad for gout. it is worth remembering that the main thing that triggers UA levels in the diet are purines: very different molecules to proteins. But, the truth is that many foods that are high in purines are also rich in proteins e.g. legumes, meat; and this is where the misconception usually arises. Now I will start talking about the individual foods and nutrients that appear to increase or lower the risk of gout.
Meat & Fish
Many scientific studies have found a strong link between consumption of red meats and fish and the incidence of gout attacks; meanwhile poultry does not appear to raise the risk of gout significantly. Furthermore, red meat consumption appears to increase the risk of gout to a greater extent than fish. One large study found out that each daily red meat portion raised the risk of gout by 21%, while each fish portion increased the risk by just 7%. The mechanism why red meat triggers gout attacks in people with high UA levels is multi-factorial. It is widely known that both fish and meat have many purines, which are eventually degraded into UA by the body; favouring their build-up which may lead to crystal formation and joint inflammation. Additionally, scientists are pointing out that the large quantities of saturated fat present in red meat affect the capacity of the kidneys to filter UA out of the blood; hence contributing to gout. This may partly explain why fish, which is lower in saturated fats than red meat, does not increase the risk of gout as much as red meat. What this suggests is that people at risk from gout should eliminate red meat completely and limit fish consumption. Although fish like salmon raises UA levels and the risk of gout, it provides essential nutrients such as Omega-3 and Vitamin D which are absent from nearly any other food. Individuals are advised to eat one portion of oily fish and another portion of white fish every week in order to get these essential nutrients. Additionally, they can eat poultry such as chicken; but they should only eat the low fat parts such as the breast.
Although legumes such as beans and lentils were met with great scepticism in the past due to their great purine content, studies in the last decade are showing that they may actually be beneficial. Recent studies have found no link between consumption of legumes and the incidence of gout attacks. Although purines are normally converted to UA, legumes contain compounds known as flavonoid glycosides that block the action of an enzyme which turns purines into UA (figure 2).
Figure 2. (a) Although legumes are a rich source of purines; they do not seem to raise the risk of gout. (b) The abundant flavonoid glycosides found in legumes block the action of an enzyme called Xanthine oxidase, which is responsible for breaking purines into UA.
Many epidemiological (statistical) studies have shown that many gouty patients drink in excess. Some drinks increase the risk of gout more than others: beer is the worst alcoholic drink due to its high purine content, while wine appears to be fine so long as it is consumed in small quantities. In general, when alcohol is consumed our body breaks it down to produce lactic acid. This lactic acid is then eliminated by exactly the same section of the kidney that normally filters UA out of the blood. In other words, the extra lactic acid produced as a result of alcohol metabolism competes with UA and reduces its filtering from the blood.
Researchers have identified that fructose is able to exert a direct effect on UA metabolism, favouring its build up. Studies have shown that drinking sodas and other drinks containing high amounts of fructose significantly increase UA levels and the risk of gout. Men and women that consumed two or more sweetened drinks on a daily basis were twice as likely to suffer from gout than individuals drinking them less than once a month. Additionally, healthy things like fruits which are rich in fructose also appear to raise the incidence of gout among people with high UA levels. Individuals at risk of gout should try and avoid drinking sweetened drinks and eat fruits in moderation. Although fruits can contribute to gout, they are still an essential source of vitamins and minerals and should be eaten. Furthermore, by consuming them whole instead of having them as juice means that you get all the fibre: this in turn slows down the absorption of fructose into the body.
Many studies have shown that consumption of dairy products is beneficial for gouty patients as it reduces UA levels. From the evidence, low-fat dairy products appear to be the most effective at reducing the risk of gout. In one study, people that were given a dairy-free diet showed higher levels of UA than those taking dairy on a daily basis. Another statistical study showed that people drinking two or more glasses of milk per day where half as likely to suffer from gout than those that drank milk less than once a month. Components in dairy foods such as lactose and galactose have been shown to activate transporters that pump UA out of the body, thus favouring its elimination.
One magic bullet that has been shown to reduce the incidence of gout attacks is the tasty cherry fruit. Both consumption of cherries or cherry extracts a few times a week appears to drastically lower the risk of gout. This fruit is likely to exert its beneficial effects due to its anti-inflammatory action and by helping the kidneys to filter UA out of the bloodstream.
Losing weight is essential in order to reduce the risk of suffering from future episodes of gout. This of course only applies to those that are overweight and individuals in a healthy range should not try losing weight. Furthermore, losing weight very quickly has been shown to greatly increase UA levels; however it appears to be fine to lose weight moderately i.e. 1 kg per week. Other things that are important include: an adequate intake of Vitamin C, fibre and to drink at least 2 litres of water a day.
Figure 3. There are certain foods that make it harder or easier for the kidneys to filter out UA. The detrimental foods include: most alcoholic drinks, red meat and sweetened drinks. Meanwhile, fish and fruits do not affect the kidneys in a negative way, but they should be consumed with moderation. On the other hand, things like legumes, vegetables, dairy products, vitamin C and cherries make it easier for the kidney to filter out UA and they should all be included in the diet.
Overall, people with high UA levels that are at risk of suffering from gout should try to eliminate all red meat from their diets; while two portions of fish should be included per week. Meanwhile, legumes and vegetables are safe and can even be beneficial, although more scientific studies are needed to fully confirm this. The best thing to do is to choose legumes that are low in purines. Furthermore, individuals should try to limit the amount of fructose from their diet. Nonetheless, eating a maximum of five pieces of whole fruit on a daily basis is healthy and will only raise the risk of gout slightly. What really appears to be essential and should be consumed in moderate amounts on a daily basis are low-fat dairy products. The evidence strongly shows that they are effective at lowering UA levels and at reducing the risk of suffering gout attacks.
Álvarez-Lario, B. & Alonso-Valdivielso, J.L. (2014). Hiperuricemia y Gota: el Papel de la Dieta. Nutrición Hospitalaria, 29(4), 760-770.