“Camomile tea 'can help keep diabetes under control'”, reports the Daily Mail . A new study has suggested that “the drink lowers blood sugar levels and can help prevent complications arising from the condition, including blindness, kidney disease, and nerve and circulatory damage”, the newspaper says.
These findings come from a study in rats, and Dr Victoria King, of Diabetes UK, is quoted as saying that, “More research would be needed before we can come to any firm conclusions about the role camomile tea plays in fighting diabetes-related complications.”
It is far too early to suggest that camomile tea might help prevent the serious complications that can result from diabetes. People with diabetes should continue to follow their doctor’s instructions about diet, exercise and treatment and should only drink camomile tea if they like it, not in the hope that it will alleviate their diabetes.
Where did the story come from?
Dr Atsushi Kato and colleagues from the University of Toyama in Japan and the Institute of Grassland and Environmental Research carried out this research. No sources of funding for the study were reported. It was published in the peer-reviewed_ Journal of Agricultural and Food Chemistry._
What kind of scientific study was this?
This was an experimental laboratory study looking at the effects of camomile tea and its chemical components on cells in the laboratory and in a rat model of diabetes. The researchers wanted to see whether camomile tea might be able to prevent the high levels of sugar in the blood (hyperglycaemia) that occur in diabetes or prevent some of the complications associated with diabetes.
The researchers carried out a number of experiments looking at the properties of camomile tea and some of its chemical components (including esculetin and quercetin). In one of these experiments, they fasted male rats overnight and then fed them a sugar solution. At the same time, they gave the rats one of the following: a camomile extract prepared in hot water (500 mg/kg bodyweight), esculetin (50 mg/kg), quercetin (50 mg/kg) or a control (salt) solution. They then monitored the rats’ blood glucose levels over a period of 120 minutes.
In a second experiment, the researchers took rats and treated them with a drug called streptozocin that causes them to develop diabetes. They then divided the rats into four groups. The groups were given either camomile extract prepared in hot water (500 mg/kg/day), esculetin (50 mg/kg/day), quercetin (50 mg/kg/day) or no treatment for 21 days. They also included a group of normal rats that had not been treated with streptozocin. They monitored the rats’ blood glucose levels at the start of the experiment and again after 21 days. They also measured how much glycogen, a compound made up of a chain of many glucose molecules, was being broken down in the liver (breakdown of glycogen can contribute to the development of hyperglycaemia).
The researchers also carried out a number of experiments in cells in the laboratory or on chemicals in test tubes, to look at the effects of camomile tea and some of its chemical components (such as esculetin, quercetin, umbelliferone and luteolin) on enzymes that play a role in diabetes and on processes that are linked to complications in diabetes. For example, they looked at their effects on an enzyme called aldose reductase (ALR2) when mixed together in a test tube (in vitro ). They also looked at the effects of camomile and its components on the accumulation of sorbitol in human red blood cells in the laboratory. The activity of the ALR2 enzyme and the accumulation of sorbitol are both thought to play a role in the development of diabetic complications, such as those involving the kidneys (nephropathy), the eyes (cataracts and retinopathy) and nerve cells (neuropathy).
What were the results of the study?
The researchers found that feeding mice a sugar solution increased their blood glucose rapidly over 30 minutes, and that levels gradually returned to normal over 120 minutes. Giving the rats esculetin, quercetin or a camomile hot water extract at the same time reduced their blood glucose levels at 30 and 60 minutes, with esculetin having the greatest effect.
When the researchers gave these treatments to diabetic rats for 21 days, they found that the camomile hot water extract, quercetin and esculetin all reduced the rats’ blood glucose levels compared with no treatment, although levels were still higher than in non-diabetic rats. The camomile hot water extract and quercetin both reduced the breakdown of glycogen stored in the liver, but esculetin did not.
In their other experiments, the researchers found that the camomile hot water extract inhibited the action of the enzyme ALR2 in vitro . Some of the components of camomile (umbelliferone, esculetin, luteolin and quercetin) prevented sorbitol from accumulating in red blood cells when they were incubated with a high glucose solution in the laboratory.
What interpretations did the researchers draw from these results?
The researchers concluded that, “daily consumption of camomile tea with meals could be potentially useful in the prevention and self-medication of hyperglycemia and diabetic complications”.
What does the NHS Knowledge Service make of this study?
Although this study provides an insight into the effects of camomile and its components on rats and cells in the laboratory, the extrapolation of these findings to humans is very premature. In particular, the experiments relating to their effects on diabetic complications only are at a very early stage and should certainly not be taken as proof that camomile tea could prevent or improve these very serious conditions. People with diabetes should continue to follow their doctor’s instructions about diet, exercise and treatment, and should only drink camomile tea if they like it, not in the hope that it will alleviate their diabetes.
Sir Muir Gray adds...
Unless you like the taste, stick to the good old breakfast tea and if you want to control your diabetes better don’t take camomile but a walk-a-mile; walk an extra 30 minutes a day.