Monday September 29 2014
Montmorency cherries come from North America
“Daily drinks of cherry juice concentrate could help thousands of patients beat gout,” the Mail on Sunday reports.
This headline is based on a small study that found drinking tart cherry juice twice a day temporarily lowered the blood uric acid levels of 12 young healthy volunteers for up to eight hours after they consumed the drink. This is of potential interest, as high levels of uric acid can lead to crystals forming inside joints, which triggers the onset of the painful condition gout.
Somewhat puzzlingly, the study recruited healthy young volunteers who didn’t have gout. A more relevant study design would have included people with a history of gout, to see what effect, if any, cherry juice had on them.
So, based on this study alone, we cannot say that drinking cherry juice helps prevent the onset of gout, or the recurrence of gout in those who have had it before. It is not clear whether reductions in uric acid of the magnitude found in this study would be sufficient to prevent gout or relieve gout symptoms.
The Mail on Sunday’s assertion that “now doctors say drinking cherry juice daily could help beat the condition” is not backed up by this research alone, nor is health advice on gout from health professionals likely to change based on this small study.
Where did the story come from?
The study was carried out by researchers from the UK and South Africa, and was part funded by Northumbria University and the Cherry Marketing Institute. The latter is a non-profit organisation, funded by cherry growers, with a brief to promote the alleged health benefits of tart cherries.
This obviously represents a potential conflict of interest, although the research paper says, “The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.”
The study was published in the peer-reviewed Journal of Functional Foods.
The Mail on Sunday’s coverage over-extrapolates the findings of this small study involving healthy people, not gout sufferers. While it is plausible that cherry juice may be of some benefit to people affected by gout, this is currently unproven.
What kind of research was this?
This was a single blind randomised crossover study testing the effects of two doses of cherry juice on levels of uric acid (urate) in the body.
The researchers say that nutritional research has focused more on the use of foods for improving human health, and particular attention has been placed upon foods containing high concentrations of anthocyanins – such as tart cherries.
Gout is a type of arthritis, where crystals of sodium urate form inside and around joints. The most common symptom is sudden and severe pain in a joint, along with swelling and redness. The joint of the big toe is commonly affected, but it can develop in any joint. Symptoms develop rapidly and are at their worst in just six to 24 hours. Symptoms usually last for three to 10 days (this is sometimes known as a gout attack). After this time, the joint will start to feel and look normal again, and the pain of the attack should disappear completely. Almost everyone with gout will have further attacks in the future.
People with gout usually have higher than normal urate levels in their blood, but the reasons for this may vary; for example, some people may produce too much urate, while in others the kidneys may not be so effective at filtering out urate from the bloodstream. The condition may run in families.
This study did not study people with gout, but only looked at the concentration of sodium urate (uric acid) in the blood of healthy young people who did not have gout or high levels of sodium urate, suggesting that they would develop gout in the near future. Hence, it does not provide good evidence that the cherry juice was beneficial to relieve gout symptoms or prevent the recurrence of symptoms.
A randomised control trial including people with gout, or people more likely to develop gout (such as older men with a family history), would be required to give us better evidence on the issue.
What did the research involve?
The research took 12 healthy volunteers (average age of 26 years, 11 of which were male) and gave them two different volumes (30ml and 60ml) of concentrated cherry juice mixed with water, to see what effect this had on measures of uric acid activity and inflammation up to 48 hours later – both of which are biological measures indirectly related to gout.
None of the volunteers actually had a history of gout.
In an effort to reduce other dietary sources of anthocyanins (outside of that gained from the cherry juice), participants were requested to follow a low-polyphenolic diet by avoiding fruits, vegetables, tea, coffee, alcohol, chocolate, cereals, wholemeal bread, grains and spices for 48 hours prior to, and throughout each arm of the trial. Food diaries were completed for 48 hours before, and throughout, the testing phase to assess the diet for compliance.
Participants were required to attend the start of each phase of the study at 9am, following a 10-hour overnight fast to account for diurnal variation. Each phase was comprised of two days supplementation with cherry concentrate. One supplement was taken immediately following a morning blood and urine sample, and a second consumed prior to each evening meal.
Multiple supplements were administered to identify any cumulative effects. The length of the supplementation phase (48 hours) was chosen due to the short period of time in which anthocyanins are metabolised.
What were the basic results?
The main results were as follows
- Blood urate (uric acid) concentrations in the volunteers went down for both the low and high doses of cherry juice in about the same amount, from around 500 micoMol per litre at the start to around 300 micoMol per litre after eight hours. The concentrations at the 24-hour and 48-hour time points appeared to have increased back up to the 400 micoMol per litre.
- The amounts of urate (uric acid) removed from the body via urine increased, peaking at two to three hours. The amount excreted then dipped but remained broadly above the starting level up to 48 hours.
- Levels of a general blood inflammatory marker (high sensitivity C-reactive protein; hsCRP) decreased.
- There was no clear dose effect between the cherry concentrate and the biological findings.
How did the researchers interpret the results?
The researchers said, “These data show that MC [Montmornecy tart cherry concentrate] impacts upon the activity of uric acid and lowers hsCRP, previously proposed to be useful in managing conditions such as gouty arthritis; the findings suggest that changes in the observed variables are independent of the dose provided.”
They also said, “these results provide rationale for the use of Montmorency cherry concentrate as an adjuvant therapy to NSAIDs [non-steroidal anti-inflammatory drugs] in the treatment of gouty arthritis [gout].”
This small study found that drinking tart cherry juice twice a day temporarily lowered the blood uric acid levels of 12 young healthy volunteers without gout, up to eight hours after they consumed the drink. The levels began to increase back to the starting levels after 24-48 hours. The researchers and media extrapolated this finding to mean that the drink may be useful for gout, which is caused by an excess accumulation of uric acid crystals.
Based on this study alone, we cannot say that drinking cherry juice helps prevent the onset of gout, or the recurrence of gout in those who have had it before. The study did not test the effect of the juice on people with gout, or those likely to get gout in the future, so is only indirectly relevant to these groups. For example, it is not clear whether reductions in uric acid of the magnitude found in this study would be sufficient to prevent or treat gout in people with a propensity for high uric acid levels in the body (for whatever reason).
Furthermore, there may have been other dietary factors contributing or interacting with the cherry juice compounds that could account for the changes observed. Hence, cherry juice might not be the sole cause of the effects seen.
The Mail on Sunday carried a useful quote from a UK Gout Society spokesman, who said that while “Montmorency cherries [those used in the study] could help reduce uric acid levels in the body, ‘People with gout should go to their GP because it can be linked to other conditions such as stroke and psoriasis’”.
We find no evidence to support the Mail’s comments that “Now doctors say drinking cherry juice daily could help beat [the] condition”.
For the reasons above, this study alone provides weak evidence that concentrated cherry juice might help those with gout. The media have somewhat overhyped the significance of the findings, which are underdeveloped and tentative. The hype would be justified if a more robust study of people with gout had been undertaken.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.