Poziom trudności: B1
Oryginał: Jessica Brown, BBC Future,
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Are there health benefits to eating turmeric and other spices?
Chilli, turmeric and other spices are often claimed to have health benefits or even the ability to "boost our immune system". But can spices really add any health benefits to our food, or help us ward off illness?
Spices have been a part of our diets for thousands of years – it's second nature to sprinkle our chips with pepper, sip on ginger tea and add chillies to our meals. But recently, some spices have been unofficially promoted from everyday culinary staples to all-healing superfoods.
But do spices really add any health benefits to our food, or help us ward off illness? And can any of them actually do us harm?
One of the most well known and widely used spices are chilli peppers. Many studies have examined their potential effects on our health – but have found both beneficial and adverse results.
Capsaicin is the main active ingredient in chillies. When we eat chillies, capsaicin molecules interact with the temperature receptors in our bodies, sending signals to the brain to create the feeling of heat.
Some studies point to the idea that capsaicin may help you live longer.
"The major findings were that higher intake of spicy foods is related to a lower risk of mortality, particularly deaths due to cancer, heart disease, and respiratory diseases," says researcher Lu Qi, professor of nutrition at Harvard's school of public health.
This does not, however, mean that starting to eat large quantities of chilli peppers will protect your health – or protect you from respiratory illness – in the short-term.
It's important to remember that the China study followed people for a median time of seven years each. So even if chillies had a protective effect on participants’ health, rather than the people who ate chillies happening to be healthier to begin with, the effect likely built up over time – not within weeks or months.
Qi tried to separate the effects of chilli consumption from everything else by controlling for age, sex, education level, marital status, diet and lifestyle factors including alcohol intake, smoking and physical activity. He says the lower risk of disease relating to eating chillies may be partly due to capsaicin.
"Certain ingredients in spicy foods, such as capsaicin, have been found to improve metabolic status, such as lipid profiles" – cholesterol in the blood – "and inflammation, and these may partly account for the observations in our study", says Qi.
The burning sensation that comes with eating chillies has long fascinated scientists. It also gives us some insight into why chillies may be associated with cognitive decline: the sensation is the result of plants evolving to protect themselves against diseases and pests.
"While some plants have evolved to become bitter or spicy to predators, it’s better if the plant can make themselves toxic, too," says Kirsten Brandt, senior lecturer at the Human Nutrition Research Centre Population Health Sciences Institute at the UK's Newcastle University.
But these compounds generally have a smaller effect on us than on insects. "A little bit of toxin can be good, such as caffeine, which speeds up our metabolism so we feel more awake," she says. "However, a lot of it is bad for you."
The compounds that give spices their flavour aren’t harmful to humans, argues Duane Mellor, dietician and senior teaching fellow at Aston Medical School in Birmingham, UK.
"While a lot of the pigments and bitter flavours we tend to enjoy in foods are there to protect plants being eaten by insects, we've grown accustomed to these flavours’ toxicity levels – we can deal with a lot of these plant compounds, including tannins in black tea, whereas some species can't."
On the other hand, even if a compound within a certain spice may have beneficial effects, we normally don’t consume enough of it to make any difference.
Robust evidence for turmeric being beneficial, however, is lacking.
In the Western world, this increasing interest in spices including turmeric as an alternative medicine was last seen in the Middle Ages, when spices were thought to have healing properties, says Paul Freedman, professor of history at Yale University.
"Spices were used to balance the properties of food. People thought of food as having hot, cold, moist and dry qualities, and they needed balance," says Freedman. Fish was considered cold and wet, for example, while spices were hot and dry.
In many Western countries, where such ideas are much newer, "this idea of balance is shared with modern new-age medicine", Freedman says. "Our modern fascination with spices brings us closer to a medieval outlook than 50 years ago – when there was a wall between modern medicine like antibiotics and superstitious medicine of the past that didn’t work."
As part of her job, Kathryn Nelson, former research assistant professor at the University of Minnesota's Institute for Therapeutics Discovery and Development, looked at molecules to see if they could be a compound for new drugs. She decided to study curcumin after she kept coming across the health claims associated with it.
"Researchers are able to exert effects in cells grown in test tubes by adding compounds to it and seeing what happens to the cells," she says.
There could be something about turmeric that's beneficial, but it’s not curcumin, she says. Plus, if turmeric is cooked as part of a meal, she says, it's added alongside other foods, and heated up, so its chemical components change.
"There might be something else in turmeric worth looking at, but not curcumin, and it might not be one thing. It might need to be chemically modified or added to something to be beneficial."
She says consuming lots of turmeric isn't harmful, but she wouldn't advise using it as self-medication.
Chilli and turmeric have been widely studied, but most trials have only compared data on consumption and different health outcomes, which doesn't separate cause from effect. And research done in laboratories doesn’t necessarily translate to the human body.
And as is true for so many nutritional studies, it's difficult to tease out correlation versus causation.
Take the 2019 Italian study finding that there was a lower risk of death associated with chilli consumption. It was observational, so it's impossible to know whether eating chilli made people live longer, whether already healthy people tend to consume more chilli, or if something else is at work.
One clue could, however, lie in how chillies are consumed by Italians and other Mediterranean cultures, says the study's author Marialaura Bonaccio, epidemiologist at Italy's Mediterranean Neurological Institute.
"Chilli is common in Mediterranean countries," says Bonaccio. "It's mostly eaten with pasta and legumes or vegetables."
This is just one example of how spices could be indirectly beneficial – they're eaten with legumes and vegetables.
"Putting spices into meat is a well-known technique to preserve meat," he says. "The benefits of spices, therefore, may be more food preservation, rather than them having direct benefits to us. But either way, we could benefit as it still makes the food less harmful to us."
We also tend to eat chillies with vegetables – which of course benefits our health, too.
So while golden lattes won't do us any harm, we might be better off having some vegetables seasoned with a sprinkling of spices. And we certainly shouldn't rely on them as a way to ward off – or to fight – any kind of illness.