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Spicy food is delicious, but how does it affect our health?

Hosted by: Olivia Gordon

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Sources:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0070583
https://academic.oup.com/bioscience/article/49/6/453/229475
http://www.ckbiobank.org/site/
https://www.cdc.gov/nchs/nhanes/index.htm
Mortality studies:
http://www.bmj.com/content/351/bmj.h3942
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169876
Anti-cancer:
http://ar.iiarjournals.org/content/36/3/837.long
http://cancerres.aacrjournals.org/content/71/8/2809
https://pubs.acs.org/doi/ipdf/10.1021/jf506098s
https://www.ncbi.nlm.nih.gov/pubmed/24337453
Diabetes/obesity:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890380/
https://www.ncbi.nlm.nih.gov/pubmed/24941669
https://www.ncbi.nlm.nih.gov/pubmed/27174467
Salt/hypertension:
https://www.reuters.com/article/us-health-diet-sodium-spice/can-spicy-foods-curb-salt-cravings-or-lower-blood-pressure-idUSKBN1D02Z8
http://hyper.ahajournals.org/content/early/2017/10/30/HYPERTENSIONAHA.117.09950
Bacteria:
https://www.ncbi.nlm.nih.gov/pubmed/22427935
https://www.ncbi.nlm.nih.gov/pubmed/26617603

Images:
https://commons.wikimedia.org/wiki/File:Capsaicin-3D-vdW.png
Just because we need to eat doesn’t mean food has to be boring a few red pepper flakes on your pizza can really make it pop.

And according to recent research, adding spice doesn’t just improve flavor it may also have health benefits. The science is far from settled, but a couple big diet studies in China and the US have suggested that eating hot peppers helps you live longer.

And a deeper dive into the physiological effects of spice could explain why. The idea that spices can have beneficial effects isn’t new. Research has demonstrated that many popular spices have antimicrobial properties, which could slow food spoilage.

But some say eating spicy food might actually extend your life. And there is some science behind such bold claims. There was 2015 study in the British Medical Journal, for example, that found a spicy diet increased life expectancy.

The researchers used existing data from the China Kadoorie Biobank, a four year data set of detailed questionnaires and physical measurements collected from over 500,000 Chinese citizens. They found that patients who said they ate a lot of spicy food, like hot chili peppers or chili oil, had a 14% lower risk of death than those who didn’t eat spicy foods. This was mostly from reductions to cancers, heart disease, and respiratory ailments, like asthma, not food poisoning, suggesting that spice isn’t just killing microbes.

A similar study of over 16,000 American adults in 2017 came to the same conclusion. Using six years of info collected by the. National Health and Nutrition Examination Survey, researchers found that total mortality was 12% lower in people who ate hot red chili peppers compared to those who didn’t.

Both of these studies use massive data sets and included participants from a variety of education levels, lifestyles, and ethnic backgrounds, which adds to their credibility. But...just because there’s a lot of data doesn’t mean that a study is perfect. After all, these data sets weren’t designed to study the effects of hot pepper consumption — they’re just huge databases.

This means that the researchers couldn’t account for a lot of variables, like what kinds of food the peppers are being cooked in, or what other spices people might be using. Even things known to influence life expectancy weren’t discernible, like whether there were differences in how many calories the different groups ate. Plus, all of the data on eating spicy food was self reported so it’s unclear what kind of chilies were used, or how spicy the food actually was.

So, even though scientists have found a trend in the data, it’s not exactly case closed. Even the researchers involved weren’t convinced. Benjamin Littenberg, one of the co-authors of the 2017 study, told the New York Times that the evidence wasn’t strong enough to make him change his diet.

But the idea that spice improves your health does make some sense, given the physiological effects of capsaicin the main chemical behind peppery heat. Capsaicin binds directly to vanilloid-receptors on sensory neurons in the tongue, triggering the neurons to spit off signals to your brain. These receptors are actually thermoreceptors they detect literal heat, hence why spicy food feels hot.

But the signals they send aren’t limited to temperature. Some research in mice has found that when capsaicin binds to TRPV1 receptors, a type of vanilloid receptor, it can trigger an increase in levels of adiponectin. That’s a hormone involved in regulating the sugars in your blood, and it’s linked to both obesity and diabetes.

Adiponectin is thought to be important for preventing insulin resistance, a condition where your body doesn’t respond as well to insulin, which can lead to type 2 diabetes. And levels of adiponectin are lower than normal in patients with obesity. Other research suggests capsaicin might also encourage the generation of brown fat sometimes called the “good” kind of fat which helps burn energy to keep you leaner overall.

When researchers fed mice a high-fat, obesity-inducing diet, those that were also fed capsaicin didn’t become obese. They also had increased expression of genes linked to the conversion of white fat into brown fat. All of this might help explain the mortality patterns, because obesity and diabetes also increase your risk of chronic diseases like heart disease and cancer.

But on top of that, there’s some evidence that capsaicin could have more direct cancer-fighting effects. Treating cancer cells with capsaicin seems to inhibit their growth and promote programmed cell death. And studies in mice suggest it might even help prevent angiogenesis, that’s the growth of new blood vessels.

Since cancer cells need blood to provide nutrients so they can grow, blocking angiogenesis can help shrink or even kill tumors. That said, we don’t know if this happens in people that eat hot peppers. And it might not even be the capsaicin on its own it could be that eating spicy foods encourages other dietary changes that have beneficial effects.

A study from 2017 surveyed over 600 people in China and found that those who loved spicy food likely ate about 3 fewer grams of salt per day than those with little tolerance for spice. In taste tests, capsaicin made controlled solutions taste saltier, so that could explain the difference. The spice lovers also had lower blood pressure, which makes sense, since eating too much salt has been linked to high blood pressure and other health problems although the connection isn't simple, and not all researchers agree.

So people who love spicy things might unconsciously be eating less salt because they think their food is saltier than it is and living longer because of that. Or, the big data studies might be cluing in on something else entirely it’s really tough to tell. Diet studies are complicated, and “spicy food” is really vague.

While consuming capsaicin might have health benefits, there’s a lot more to be done to confirm them, especially since studies in a dish or a mouse don’t necessarily translate to the human body. So even though there’s evidence that people who say they eat a lot of spicy food live longer, it’s not totally clear if that’s because of the spicy food. That said...eating that sizzling Szechuan probably won’t hurt… except maybe the day after!

Thanks for watching this episode of SciShow! If you want to better understand how chilies feel warm, you can check out our episode on why spiciness feels hot and mint feels cool.