Chilli may lower blood pressure, scientists say

Spicy food flavoured with hot chilli peppers contains a natural chemical ingredient that may lower blood pressure, according to a study on a strain of laboratory rats with hypertension.

Scientists have discovered that the long-term ingestion of capsaicin, the ingredient in chillies that makes them taste hot, can reduce blood pressure – at least in rats.

Previous studies have produced mixed results when it comes to finding a link between hot chillis and blood pressure, but this may be because they were carried out over relatively short time periods, the scientists said.

The latest findings are the first to establish a link between the ingestion of capsaicin over a longer period of time and a subsequent lowering of blood pressure in animals genetically predisposed to having hypertension.

"We found that long-term dietary consumption of capsaicin, one of the most abundant components in chilli peppers, could reduce blood pressure in genetically hypertensive rats," said Zhiming Zhu of Third Military Medical University in Chongqing, China.

The study, published in the journal Cell Metabolism, suggests that capsaicin works by activating a special "channel" in the lining of the blood vessels called the transient receptor potential vanilloid 1 (TRPV1). When the channel is activated, it increases the production of nitric oxide in the blood vessels that is believed to protect against inflammation and other vascular problems.

The scientists said the study on the rats now needs to be confirmed by analysing any epidemiological association between eating chilli peppers and blood pressure. Dr Zhu said one clue came from China, where the prevalence of hypertension is greater than 20 per cent in the north-eastern regions of the country, but between 10 and 14 per cent in souther-western regions such as Sichuan where spicy food is more commonly eaten.

"People in these regions like to eat hot and spicy foods with a lot of chilli peppers. For example, a very famous local food in my hometown, Chongqing, is the spicy hot pot," Dr Zhu said.

He added that eating hot, spicy food may not be necessary to gain the benefits of chillis because similar compounds are present in sweet peppers. There is, for instance, a mild Japanese pepper, which contains a compound called capsinoid that is closely related to capsaicin. "Limited studies show that these capsinoids produce effects similar to capsaicin. I believe that some people can adopt this sweet pepper," Dr Zhu said.