Chilli pepper, a rich source of antioxidants, has previously been linked to inhibiting the growth of pancreatic cancer cells, and has been suggested to cut fat and energy intake when added to the diet.
And now researchers from the University of Tasmania have reported the findings of small human trial, which showed that regular consumption of a chilli-containing meal could improve insulin control by about 60 per cent.
Thirty-six people were recruited (22 women, average BMI 26.3 kg per sq. m) to participate in the randomised, crossover, intervention study. The subjects ate their normal (bland) diet for four weeks, and then crossed over to the chilli-diet for a further four weeks. The chilli blend was provided by MasterFoods, Australia who also reported that the capsaicin content was about 33 mg per 30 grams of chilli blend.
The researchers did not attempt to extract the capsaicin, the active ingredient that gives the chilli its heat, and it should be noted that chilli also contains antioxidants such as lutein, vitamin C, and beta-carotene.
Blood samples were taken to measure levels of serum glucose, insulin and C-peptide, used as another measure of insulin levels - insulin is produced by splitting so-called pro-insulin, which forms one insulin molecule and one C-peptide.
It was found that after the chilli diet regime the blood glucose levels increased less that for the bland diet.
Blood insulin levels for the chilli group increased by only 69 micro-International Units per millilitre (mcIU/mL) of serum, compared to the increase of 109 mcIU/mL measured after the bland meal consumption.
The ratio of C-peptide to insulin, a measure of insulin clearance, was also significantly improved during the chilli diet regime, said the researchers (12.4 for the bland diet and 14.1 for chilli diet).
"Chilli meals possibly result in lower C-peptide and insulin secretion and higher hepatic clearance of insulin, and the effect is larger is chilli is eaten regularly," wrote lead author Kiran Ahuja in the American Journal of Clinical Nutrition (Vol. 84, pp. 63-69).
The mechanism could not be identified, although the researchers suggest that compounds in chilli act on receptors in the liver, which subsequently affects insulin production and/or clearance.
"Additional research is needed to confirm this finding in persons at higher risk of hyperinsulinemia and to determine whether an improved insulin response might , however, induce negative effects on thermogenesis in overweight and obese persons," concluded Ahuja.
Some caution should also be exercised as high intake of hot chillies has been linked with increased risk of stomach cancers in the populations of India and Mexico.
An estimated 19m people are affected by diabetes in the EU 25, equal to four per cent of the total population. This figure is projected to increase to 26m by 2030.
In the US, there are over 20m people with diabetes, equal to seven per cent of the population. The total costs are thought to be as much as $132bn, with $92bn being direct costs from medication, according to 2002 American Diabetes Association figures.