Before discussing whether sour cherries effectively lower uric acid, let's first understand the relationship between sour cherries and cherries.
These two are indeed within the same category, but if we were to differentiate them based on cultivation varieties, there is indeed a world of difference.
The first category is Chinese cherries.
Characterized by thin skin, soft and juicy flesh, and relatively
large seeds, Chinese cherries have the drawback of an extremely short storage period. However, they are deliciously sweet and sour. With the extensive promotion of cherries in recent years, Chinese cherries are mostly limited to consumption within the local planting areas.
The second category is cherries, commonly known as "Cherries".
There's no need for much explanation here; it's undoubtedly the most popular variety sold currently. Cherries typically have thicker skin and firmer flesh compared to Chinese cherries. Some varieties even have higher sweetness levels than Chinese cherries, such as the Topaz cherry.
The third category is sour cherries
Primarily originating from Europe, hence commonly referred to as "Prunus cerasus". Compared to the previous two members, sour cherries are smaller in size, lower in sweetness, and have a distinctly sour taste, hence the name "sour cherries". They are not suitable for direct consumption as fruit.
Today, the star we are discussing is the sourest and least palatable variety—sour cherries. Despite their unappealing taste, they are considered valuable due to their numerous health benefits, making them one of the most sought-after plant-based ingredients globally.
The key active components in sour cherries are incredibly
numerous and present in remarkably high concentrations, with some components reaching extraordinary levels.
Nutrient Content and Minerals
Sour cherries contain a significant amount of vitamins, such as vitamin A and vitamin C, which can account for over 20% of the fresh weight. The levels of vitamin B1 and B2 are also very high. Among the mineral elements, the ones most familiar to everyone are iron and calcium. Taking iron as an example, the iron content in sour cherries per unit weight can even reach 30 times that of apples.
Anti-inflammatory and Antioxidant Proanthocyanidins and Anthocyanins
Proanthocyanidins can be converted into anthocyanins in acidic environments, and sour cherries are extremely rich in proanthocyanidins, with levels reaching as high as 200mg/kg, making them the king of proanthocyanidins.
Although the active ingredient content in the cherries we commonly consume daily is already quite high, when compared, the levels of anthocyanins and other polyphenolic active ingredients in sour cherries are several levels higher.
Another active ingredient that is often overlooked is melatonin.
Melatonin is a hormone originally secreted by the pineal gland in humans or mammals, formed through the conversion of serotonin. Scientists later discovered that melatonin may also be abundant in many plants, vegetables, and fruits, such as cabbage, bananas, tomatoes, and sour cherries.
Especially in sour cherries, the content of melatonin is very high, even exceeding the levels of melatonin found in mammalian blood.
Various organic acids are active substances.
The reason sour cherries can make one "sour to the teeth" is because they contain a very high content of various organic acids, such as chlorogenic acid. This is the key reason for their poor taste.
Clinical Efficacy of Sour Cherries
Lowering Uric Acid Levels
The current known mechanisms by which sour cherries intervene in uric acid and gout can be summarized as follows:
■ First, inhibition of uric acid production. The abundant anthocyanins and flavonoids in sour cherries can inhibit the activity of xanthine oxidase in the liver. Xanthine oxidase is a key enzyme in the process of uric acid production, and inhibiting its activity can reduce the production of uric acid. This mechanism is similar to that of the uric acid-lowering drug allopurinol.
■ Second, promoting uric acid excretion. Sour cherry extract can enhance the function of uric acid transport proteins in the kidneys, increasing the excretion of uric acid from the kidneys. This can be helpful in reducing uric acid levels in the blood.
As for whether it's really effective, more research and clinical studies are needed to confirm.
Sour cherry juice can inhibit the activity of hepatic xanthine oxidase, thereby reducing serum uric acid levels in hyperuricemic rats.
As early as 20 years ago, researchers at the University of California conducted a small-scale human trial demonstrating that consuming cherry products could lower serum uric acid levels within a few hours.
In 2019, the results of another clinical trial involving 26 obese and overweight patients showed that consuming sour cherry juice for one month not only significantly reduced serum uric acid levels but also simultaneously decreased the levels of CRP and monocyte chemoattractant protein in the experimental group. This alleviated hyperuricemia associated with gouty arthritis.
Another clinical study, published in 2023 and focusing on gout symptoms, is also highly significant. In this study, 282 patients with gout were randomly divided into three groups and treated with sodium bicarbonate, citrate preparations, and sour cherry preparations, respectively, in a randomized controlled trial that lasted for three months.
After the trial concluded, there was a significant decrease in serum uric acid levels and an increase in urine pH values in all three groups of participants. However, the group treated with sour cherry preparations exhibited a greater decrease in the urine albumin-to-creatinine ratio (UACR), experienced fewer gout attacks, and showed lower levels of C-reactive protein after three months compared to the other groups.
Sour cherry extract, when used in the intervention of gout, not only reduces the frequency of attacks but also provides additional protection for the kidneys.
The intake of cherries can reduce the risk of recurrent gout attacks by 35%. What's more interesting is that when allopurinol (the most commonly used uric acid-lowering medication) and cherries are taken together, the risk of gout attacks decreases by a significant 75% compared to periods without either treatment.
Despite the abundance of evidence, there are still differing opinions within the academic community. A clinical study published in the Journal of Rheumatology in 2020, involving 50 patients with gout, indicated that sour cherry juice did not demonstrate a more significant reduction in serum uric acid levels, either after a 28-day intake period or within 24 hours of intake.
Debate is a healthy part of academic discourse, but regardless, sour cherry (or cherry) extract has begun to be included in the dietary consensus for gout prevention and treatment in some countries. In the final section of the gout dietary guidelines in Austria in 2022, there is a suggestion to support the association between consuming cherries and lowering uric acid levels, recommending their incorporation into daily dietary interventions for gout.
Improvement in Heart Health
A 3-month intervention trial was conducted on 19 adults aged 20 to 60 with metabolic syndrome. The intervention group was required to consume 240ml of sour cherry juice daily, while the control group received a placebo of equal caloric content.
After 3 months, the intervention group members who consumed sour cherry juice showed significantly lower levels of low-density lipoprotein (LDL) in their blood compared to the control group. Total cholesterol also exhibited a more pronounced decreasing trend. Therefore, the study suggests that sour cherry juice may be helpful in attenuating the process of atherosclerosis.
Another randomized, controlled, crossover clinical study on metabolic syndrome has demonstrated that short-term supplementation of sour cherry not only reduces low-density lipoprotein (LDL) and total cholesterol but also helps lower blood pressure.
There is also significant improvement in low-density lipoprotein cholesterol in elderly individuals. In a randomized controlled trial involving 37 seniors aged 65 to 80, the intervention and control groups consumed 480 milliliters of sour cherry juice or an equal-calorie control beverage daily, respectively, for 12 weeks.
Improvement in Gut Health
Clinical studies have shown that sour cherry extract can improve the structure of the gut microbiota. Interestingly, its mechanism and results differ from those of other prebiotics or probiotics, possibly due to its particularly diverse array of active ingredients.
For example, scientists found in experiments that polysaccharides in sour cherries can significantly increase the abundance of Bacteroides species, while their high content of chlorogenic acid can greatly promote the growth of Lactobacillus species.
The recovery of muscles and endurance.
As soon as the body starts exercising, free radicals are produced internally, and not all of these free radicals are villains, as they can enhance our body's function in the short term.
The problem lies in the fact that prolonged endurance exercise can result in persistently high levels of free radicals in the body, which may damage mitochondria, leading to accelerated protein breakdown and cell apoptosis, ultimately causing muscle damage and soreness.
However, one very significant clinical benefit of sour cherries is their ability to reduce muscle pain and strength loss.
A meta-analysis in 2020, which included 10 studies, indicated that consuming sour cherries at various levels in the 7 days leading up to endurance exercise or within 1.5 hours prior to exercise significantly benefited endurance performance.
By reducing oxidative stress and inflammation levels, sour cherry powder can diminish muscle damage and soreness, thereby enhancing aerobic performance.
Several other studies have also indicated that compared to the control group, sour cherries can help muscles recover more quickly and significantly reduce inflammatory markers in the blood.
Relief of anxiety and assistance with sleep.
Due to their high content of anthocyanins and melatonin, sour cherries can inhibit the degradation of tryptophan, thus offering good improvement for individuals prone to anxiety or experiencing poor sleep due to insufficient secretion of melatonin.
Clinical results from a study in 2012 involving volunteers aged 20 to 85 demonstrated that after consuming sour cherry juice for 5 days, participants in the intervention group showed a significant decrease in cortisol levels in urine and a notable reduction in anxiety levels, while those in the control group did not.
Several other studies have separately shown that continuous consumption of cherries for approximately 7-14 days leads to a significant increase in melatonin levels in urine. Moreover, the degradation of tryptophan is notably reduced, and volunteers experience a significant improvement in both sleep duration and sleep efficiency.
Sour cherries can increase melatonin levels
Melatonin can inhibit the degradation of tryptophan
How to Choose Sour Cherry Products?
There are many sour cherry products available on the market, such as dried sour cherries, canned cherries, concentrated juices, and more. However, subsequent processing can significantly affect the retention of active compounds and nutritional components, thereby impacting their efficacy. Therefore, selecting the right type of product is crucial.
In 2012, researchers specifically tested various sour cherry products available on the market, including concentrated juices, freeze-dried sour cherries, canned cherries, and dried fruits. They compared and evaluated multiple antioxidant and anti-inflammatory indicators, including total anthocyanins, polyphenol content, oxygen radical absorbance capacity, and so on.
The results showed that among all the samples, the concentrated juice extract had the highest total anthocyanins and polyphenol content. Additionally, it exhibited the highest oxygen radical absorbance capacity (ORAC) and peroxynitrite radical avoidance capacity (NORAC).
Furthermore, the test results also revealed that all processed sour cherry products exhibited anti-inflammatory activity. However, the concentrated juice extract showed stronger inhibition of cyclooxygenase-1 (COX-1) activity compared to other processed products. Hence, its potential anti-inflammatory effect may be the most promising.
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