Behind the Headlines

Wednesday November 25 2009

The study did not look at conventional mint tea

“An ancient herbal mint tea from Brazil is as effective at delivering pain relief as commercial medicine,” according to The Guardian.

The news comes from a study into Hyptis crenata, a Brazilian herb that is distilled in water to make a tea-type drink. Scientists gave mice an extract of the plant and looked at their pain response, which seemed to be reduced by the extract. The study has not yet been fully published or presented, so its results should be seen as very preliminary. Also, the current implications of this animal research are very limited, and as yet there is no definite evidence of pain-relieving effects in humans.

Should future research find pain-relieving properties for humans, the chemicals responsible might be extracted and developed into a medicine. However, developing medicines is a long and complex process, and issues of safety, effectiveness, cost and how they compare to existing medicines must all be considered.

 

Where did the story come from?

These news reports are based on a forthcoming conference presentation by Graciela Silva Rocha of Newcastle University, who was the lead researcher in this study. The presentation will be given as part of the 2nd International Symposium on Medicinal and Nutraceutical Plants in New Delhi, India, and is scheduled to appear in the society’s journal, Acta Horticulturae.

As this research has not yet been published, full details of its methods and findings are not available. Some details are available from a press release from Newcastle University, and a powerpoint presentation describing some of the research. This appraisal is based on these sources. The final presentation given at the Symposium in India may differ.

 

What kind of research was this?

This research looked at the potential pain-killing properties of the plant Hyptis crenata, a type of mint that grows in western Brazil.

The researchers say that it is widely used as a traditional medicine in the area, but that it has not yet been pharmacologically researched. They say that this species of plant (Hyptis) has been reported to have therapeutic properties, such as relieving pain and fighting inflammation and cancer. Several drugs that are used today, including aspirin, originate from plants that were used for medicinal purposes in the past.

Before the research began, a survey had been conducted in 20 Brazilian people to assess their beliefs about the plant’s effects. Some of the respondents used the plant to deal with pain, most commonly by brewed into tea. A small sample of subjective opinions can be used to initially point towards a possible area for research, but it does need to be followed up by rigorous scientific testing.

The current research was an animal study which examined the pain-relieving effects of H. crenata in mice and attempted to identify the chemical components of the plant behind this action. Although studies in animals can be valuable early research, the results may not be directly applicable to humans. In addition, this study has not yet been fully published and, therefore, has not been through the peer-review process. Until it is fully published, it should be treated with caution.

 

What did the research involve?

Mice in a laboratory were given different concentrations of H. crenata, which was presumably administered as a “tea”, though this is not specifically reported. Infrared heat was then applied to the hind paw and the researchers timed how long it took for the mice to withdraw from the heat.

The researchers then compared these results to those when the mice were given an anti-inflammatory drug (indomethacin) or plain water. The study did not report what period of time elapsed between administration of the tea and the application of the heat, or how many times the test was repeated. In a second set of tests, the researchers injected the irritant acetic acid into the abdomens of the mice and counted the number of contortions they performed.

Studies in mice that involve proxy measures of pain may not be directly applicable to humans.

As a final part of the experiment, the researchers analysed H. crenata in the laboratory to see whether it contained compounds similar to salicylic acid, the active compound in aspirin.

 

What were the basic results?

The presentation reports that the pain-relieving effects of H. crenata increased over a 24-hour period following administration of either low dose (15mg/kg) or high dose (150mg/kg). This effect was found to be similar to that of the anti-inflammatory drug indomethacin, while plain water had no effect. Comparable results were seen in the experiments in which the mice were injected with acetic acid.

The researchers found that H. crenata did not contain salicylic acid.

 

How did the researchers interpret the results?

The researchers conclude that Hyptis crenata has pain-relieving properties which are effective at low and high dose. They say that future aims are to discover the active pain-relieving compounds in the plant and to understand the pain-relieving mechanisms involved.

 

Conclusion

This study appears to have very limited applications at present. Testing a sample of mice for degrees of pain relief using proxy measures does not show direct evidence of the effects on pain in humans. Although the report says that the pain-relieving effects were similar to those of the anti-inflammatory drug tested, there is no direct evidence to show that this would be the case in humans.

However, it is likely that Brazilian mint (Hyptis crenata) will be subject to further research, as chemicals derived from plants have been used as the basis of some breakthrough medications such as aspirin and digoxin. Even if these tests show promise, creating a medicine using its active ingredients could be a long and complex process, involving years of development, testing and safety checks. The research would also have to address whether such a drug would be any safer or more effective or cheaper than established painkillers such as aspirin and paracetamol.

It should also be noted that the study was on a Brazilian plant Hyptis crenata and not a cup of normal mint tea, as some headlines have implied.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Cup of mint tea is an effective painkiller. BBC News, November 24 2009

Brazilian Mint reduces pain 'as effectively as leading drugs'. The Daily Telegraph, November 24 2009

Brazilian mint tea 'as effective as pain-relief drugs'. The Guardian, November 25 2009

Links to the science

Got a pain? – Have a cup of Brazilian mint. Newcastle University, November 25 2009

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