Tuesday April 1 2014
Bergamot is a citrus fruit used to flavour teas, including Earl Grey
“A cup of Earl Grey 'as good as statins' at fighting heart disease,” reports The Daily Telegraph, entirely without proof.
The science behind this headline did not show Earl Grey was as good as statins (a class of drugs used to lower high cholesterol) in people.
The study was early stage research on a small group of rats in a laboratory. None of the research involved humans, tea, or any assessment of heart disease.
The research involved an extract called HGMF, taken from the bergamot fruit; a citrus fruit used to flavour teas such as Earl Grey.
Rats with high cholesterol levels were fed a high cholesterol diet for three weeks and given either the bergamot extract (HMGF) or the commonly used statin, simvastatin.
The researchers found that HMGF had cholesterol-lowering effects similar to that of simvastatin. Though importantly, as the research was in rats, it is not possible to say that HGMF would work the same way in humans, unless directly tested.
Furthermore, this study tested a pure extract rather than tea containing the extract, the effects of which may be different. For instance it is unclear how much Earl Grey you would need to be exposed to a comparable level of HGMF; it may take gallons of the stuff.
This study is absolutely not a reason to stop taking prescribed statins to replace them by drinking Earl Grey tea as this could be dangerous.
Where did the story come from?
The study was carried out by researchers from the University of Calabria (Italy) and was funded by the Italian National Project.
The study was published in the peer-reviewed Journal of Functional Foods.
The Daily Telegraph and the Mail Online reporting was potentially misleading and arguably irresponsible.
While the main body of the article was factually accurate, the headlines (one of which was on the front page of the Telegraph) implied that drinking Earl Grey tea had been proven to be as effective as statins.
Statins are known to be effective and have a large weight of evidence from human research proving this. By contrast, the effects of Earl Grey tea, as far as we are aware, have barely been researched, so they are not on an equal playing field. So suggestions that Earl Grey is “just as effective” are unfounded.
This could have encouraged people who had been prescribed statins, some of which are at high risk of experiencing a cardiovascular disease such as a heart attack or stroke, to stop taking their medication.
What kind of research was this?
This was an animal study looking at the effect of bergamot extract on the cholesterol profile of rats with high cholesterol and comparing it with a commonly used statin called simvastatin.
Statins are a class of related drugs currently used to lower cholesterol levels in people at risk of cardiovascular disease, the main cause of death in many westernised countries. The drugs lower cholesterol levels by acting on an enzyme called 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) in the body.
The researchers were looking to see if other compounds might work in a similar way to statins and affect the same enzyme. They decided to investigate bergamot (Citrus bergamia Risso), a citrus fruit widespread in the Mediterranean area.
The fruit has anecdotal cholesterol-lowering properties and the study authors said it was only toxic at very high levels, implying it might be relatively safe. The researchers state bergamot essence is used in teas, jams and sherbet, but there was no special mention of Earl Grey in the underlying research. It appears the media has made a link with this specific tea as it apparently contains high levels of the extract and is well known to a UK readership.
What did the research involve?
The study used 48 rats with high cholesterol to compare the cholesterol-lowering effects of bergamot extract 3-hydroxy-3-methyl-glutaryl flavanones (HMGF) with the commonly-used statin, simvastatin. The rats’ diets were carefully controlled so all that differed was their cholesterol treatment – bergamot or statin.
Body weight, blood cholesterol levels, cellular protein levels, liver enzyme activity and genetic regulatory mechanisms were all monitored and recoded for evidence of cholesterol-lowering properties in the different treatment groups.
Contrary to the headlines, the experiments involved a dry extract from bergamot fruit peel. Unfortunately for the rats they did not get to sample any tea, Earl Grey or otherwise.
The important measures were total cholesterol, another type of blood fat (triglycerides), and specific subtypes of cholesterol called very low density lipoproteins (VLDL), low-density lipoproteins (LDL) and high-density lipoproteins (HDL). HDLs are the so called “good” cholesterol, whereas LDLs are the “bad” cholesterol. This is a simplistic account of their roles within the body, but is sometimes useful.
Before the experiment all rats were stabilised on regular rodent food before being randomly divided into four groups of 12 animals each:
- control group: received a regular diet for three weeks
- high cholesterol control group: received a high cholesterol diet for three weeks (regular diet +2% cholesterol +0.2% cholic acid; a bile acid that has a role in fat absorption and moderating cholesterol levels)
- high cholesterol group treated with statin: received the high cholesterol diet for three weeks (regular diet +2% cholesterol +0.2% cholic acid); from the 2nd to the 3rd week each rat was given simvastatin (20 mg/kg bodyweight/day)
- high cholesterol group treated with bergamot extract HMGF: received the high cholesterol diet (regular diet +2% cholesterol +0.2% cholic acid) for three weeks; from the 2nd to the 3rd week each rat was given HMGF (60 mg/kg bodyweight/day)
The main analysis compared the cholesterol lowering effects of simvastatin with the bergamot extract HMGF.
What were the basic results?
Both the bergamot extract and simvastatin reduced total cholesterol (in blood and in the liver), triglyceride levels, and VLDL and LDL levels – the bad cholesterol. However, an increase in HDL content – the good cholesterol – was observed exclusively in the HMGF-treated rats.
Both bergamot extract and simvastatin regulated enzymes were involved in cholesterol metabolism in a similar way at a protein and gene regulation level. This implied the changes observed were not coming from some other secondary effects of the extract and were direct result of changes to how cholesterol was metabolised in the rats’ livers.
The study investigated the safety of the extract to some degree. It found the extract had a low toxicity to cells in the body, and did not cause DNA damage at doses lower than 90 micrograms per millilitre.
How did the researchers interpret the results?
The researchers stated that their study “demonstrated that the three statin-like flavanones, extracted from bergamot peel and contained in HMGF, exert a similar behaviour [in] respect to commercial simvastatin on a model of hypercholesterolaemic rats [rats with high cholesterol levels]” and that “the daily supplementation of HMGF in the diet could be very effective for the treatment of hypercholesterolaemia”.
This animal experiment indicated that the bergamot extract HMGF may have cholesterol-lowering effects similar to that of the commonly used statin, simvastatin, when given to mice with high cholesterol levels that were fed high cholesterol diets for three weeks.
The main limitation of the study was that none of the research involved humans. Therefore, it is not possible to say the bergamot extract would work the same way in humans, unless directly tested. Furthermore, this rat study tested a pure extract rather than tea containing the extract, the effects of which may be different. For instance, taking milk in tea could potentially affect how the extract is metabolised in the body compared to a pure extract.
The headlines indicated Earl Grey tea could help fight heart disease, but based on the underlying research study only, there is little evidence for that. Also the study made no assessment of the long-term health benefits of the reductions in cholesterol in the rats. For example, the effects may have been temporary.
There needs to be more robust research in humans to find out if bergamot extract holds any real promise in lowering cholesterol levels and so fighting cardiovascular diseases such as heart disease and strokes in the future.
We would not want anyone to think this research is a reason to stop taking statins and replace them with drinking tea containing bergamot extract; this could potentially be dangerous. If you have any concerns about your cholesterol levels, or any cholesterol-lowering treatments that you are currently prescribed, consult your doctor.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.