There are is a growing body of research into the effects of chillies on our health- both good and bad.
The potential for both health and harm has always been a defining characteristic of chilli peppers, and among scientists, doctors and nutritionists it remains a matter of some dispute.
A new study, published in the British Medical Journal, seemed to indicate that a diet filled with spices – including chillies – was beneficial for health.
A team at the Chinese Academy of Medical Sciences tracked the health of nearly half a million participants in China for several years. They found that participants who said they ate spicy food once or twice a week had a mortality rate 10% lower than those who ate spicy food less than once a week. Risk of death reduced still further for hot-heads who ate spicy food six or seven days a week.
Chilli peppers were the most commonly used spice among the sample, and those who ate fresh chilli had a lower risk of death from cancer, coronary heart disease and diabetes.
While the health-promoting properties of chillies may not be fully understood, at least we have a good idea where to look to find the source of them. Cut a chilli open and you will see yellow placenta-like fronds that attach the seeds to the inside of the fruit. In most types of chilli, this is the location of the spice’s secret weapon – capsaicin.
It is capsaicin that makes chillies hot. The heat is measured in Scoville heat units, which is the number of times a sample of dissolved dried chilli must be diluted by its own weight in sugar water before it loses its heat. For a green bell pepper this is zero. But habanero peppers have a Scoville value of between 100,000 and 350,000. For pure capsaicin the figure is 16 million.
While the Satanic-red horns of chillies seem to hint at their throat-scorching potential, extracted capsaicin is an odourless and colourless substance.
More importantly for humans, chillies also evolved to repel microbes. Chillies kill or inhibit 75% of such pathogens.
It is sometimes said that people in hot countries use more chilli because it makes them sweat, which cools them down. But in 1998, researchers at Cornell University pointed out that the greater use of spices in countries such as India, Thailand and China was likely to be linked to their anti-microbial function.
This correlation with climate, and the attendant risk of infectious disease, was greater than the link with the right growing conditions for the spices. In other words, humans in dangerous climates developed a taste for chilli which probably saved them a lot of death.
We now know that chillies are also a good source of antioxidants. Forty two grams of the spice would account for your recommended daily allowance of vitamin C. They are also rich in vitamin A, as well as minerals such as iron and potassium.
Capsaicin has even been touted as a potential weight-loss tool. Research conducted this year by the University of Wyoming on mice that had been fed a high-fat diet found that the molecule increased metabolic activity in the animals, causing them to burn more energy and preventing weight gain. In another study, published last month in Plos One, researchers at the University of Adelaide found that the receptors in the stomach that interact with capsaicin play a role in sensing when we are full. Previous studies on humans seem to back the idea that eating spicy food seems to curb our appetite.
The recent study in China found a correlation between the consumption of spicy food and lower rates of death from those diseases – and laboratory research from the last 10 years suggests some possible reasons for that too.
In 2012, a team of nutritionists at the Chinese University of Hong Kong, working with hamsters, found that capsaicin helped break down so-called “bad” cholesterol which might have clogged up the animals’ arteries, but it left alone the “good” cholesterol which helps remove it. There was a second benefit for cardiac health too – the capsaicin appeared to block the action of a gene that makes arteries contract, restricting blood flow.
Several studies have also indicated that capsaicin has powerful anti-cancer properties. It has been found to be helpful in fighting human prostate and lung cancer cells in mice, and there are also indications that it could be used as a treatment for colon cancer. It may also improve drug resistance for bile-duct cancer sufferers.
“There are a lot of reports that say that capsaicin may be good for human health, especially with cancer,” says Zigang Dong at the Hormel Institute of the University of Minnesota. “However, there are other reports that show totally the opposite result.”
Dong is the co-author of a 2011 review, published in the journal Cancer Research, titled The Two Faces of Capsaicin, in which claims about the spice’s benefits for health are laid alongside a long list of counter-claims, pointing to negative effects.
The report details six studies on rats and mice in which the animals developed signs of cancer in the stomach or liver after their diet was changed to include more capsaicin. Meanwhile, studies examining the effects of capsaicin on the human stomach have delivered wildly divergent results. While one showed visible gastric bleeding after consumption of red pepper, another showed no abnormalities, even when ground jalapeno peppers were placed directly in the stomach.
“Probably it is harmful in the stomach or oesophagus because capsaicin itself can cause inflammation,” says Dong. “And if anything can cause inflammation or so-called burning effect, it must cause some cell deaths and therefore the long-term chronic inflammation is maybe harmful.”
Capsaicin – and the chilli pepper – remains enigmatic. But whether it is a friend or foe, we’re exposing ourselves to it more and more. Between 1991 and 2011, global consumption of dry chillies increased by 2.5% per year, while our per capita intake increased by 130% in that time.
But after being over-stimulated the neurons stop responding, killing the pain. This process involves the release of endorphins, which can give us a “rush” not dissimilar from the feeling of having exercised well. This may explain why some people believe that hot food is addictive.