Nightshades promote inflammation

Here's a thing some people say.

Therefore, you should avoid them. All members of the Solanaceae family, which includes potatoes, tomatoes, peppers, and eggplant. They all promote inflammation. So, don't eat them. This claim is not entirely unfounded. I mean, I can't find any actual scientists who are concerned that nightshades might cause inflammatory problems, but there are scientists investigating whether nightshades might aggravate existing inflammatory problems like arthritis or colitis.

But every reputable medical scientific authority you could imagine says that you probably shouldn't worry about nightshades. The benefits of eating a diet rich in these kinds of plant foods almost certainly outweigh any detriments for the vast majority of people. Some small number of people may be particularly sensitive to nightshades, and they might benefit from eating something else. But the evidence for that is almost purely anecdotal at this point. In contrast, there is a mountain of research indicating that a diet rich in fresh fruits and vegetables, including nightshades, is fantastic for your health, including for inflammatory conditions. You will, nonetheless, find fringe sources that raise big alarms about nightshades. Let's see. "Nightshades of all types were considered inedible prior to the 1800s.".

Hah, tell that to the indigenous people of the Americas who have been living off of nightshades for thousands and thousands of years. The common food in nightshades are all indigenous to the Americas and did not appear in Afro-Eurasia until the Columbian exchange. Prior to that, yeah, Afro-Eurasian experience with this family of plants was limited to species like Atropa Belladonna, deadly nightshade. In ancient Rome, Empress Livia Drusilla was rumored to have used the juice of deadly nightshade berries to murder Emperor Augustus, her husband. But they had poisonous nightshades here in the Americas, too. And I found one in my yard the other day. Not that. That's a ground cherry, AKA Cape gooseberry, another nightshade native to the Americas.

It grows these beautiful little lanterns, which are just an overgrown version of the calyx you see at the top of an eggplant. Inside there is the tasty tomato-like fruit with a little umami, kind of like a tomato, but it's got more sugar. So, it's sort of more like a dessert. Delicious. And growing right next to that is another mini tomato looking thing that could kill you, Carolina horsenettle. Technically, that's a misnomer. It's not in the same family as nettles. It just has nasty thorns, so it reminded people of nettles.

It's a nightshade, just like tomatoes and ground cherries. And it produces a very similar fruit. Only difference is, this one can kill you, or more likely your horse, hence the name.

All nightshades do contain a category of

Nitrogenous organic compounds known collectively as alkaloids.

And some of these alkaloids are toxic, the big one being Solanine. Solanine has been shown to be a very effective insecticide. And so, that's probably one reason plants evolved to make it. It kills insects that eats the plant.

Mammals like us do not absorb Solanine very efficiently in our guts. Therefore, it is not as effective at killing us, but if we eat a ton of Solanine, we absolutely can get sick and potentially die. This is probably why we evolved to perceive Solanine and similar glycoalkaloids as being very bitter and unpleasant to the taste. If I plopped this horsenettle berry into my mouth and chewed, it'd probably taste so bitter and astringent that I'd spit it out, because evolution works. That said, just because something is bitter doesn't mean it's toxic.

Anyway, horsenettle and the other actually deadly nightshades. Yes. If I swallowed a bunch of these, I'd probably get some flu-like symptoms — vomiting, diarrhea, fever, confusion, nightmares, and yes, all kinds of inflammation, including joint inflammation. But just because a family includes a few toxic members doesn't mean that they're all bad, right? Like, some members of the Amaryllis family create dangerous amounts of toxic alkaloids. That doesn't mean onions are bad. They're in that family.

The poppy family produces an alkaloid called opiates. And you know what those do. That doesn't mean poppy seeds are bad for you. All potatoes contain some solanine, yes. But it's really only the green ones you need to worry about.

The green is not solanine.

It's just chlorophyll, but chlorophyll develops in

Response to the same conditions that prompt the potato to make solanine, namely sun exposure.

If the potato sees sun, that means it's also exposed to insects and herbivores, so it makes solanine to deter them.

And yeah, there are documented cases of people getting seriously sick from eating green potatoes, but you'd probably have to eat a whole lot of them, despite the fact that they tasted disgustingly bitter to you. The more interesting question is, do the very small amounts of glycoalkaloids we eat from nightshades all the time, might those aggravate inflammatory conditions the way some people claim they do? Here's a study that's widely cited by the anti-nightshade crowd. Canadian scientists fed deep-fried potato skins to mice. And these mice were either genetically or chemically induced to have inflammatory bowel disease. Solanine and other glycoalkaloids are concentrated around the skin, so that's why they fed them skins. And the researchers concluded that those mice showed statistically significant increases of intestinal inflammation compared to the control groups. But that's one study. It's of mice.

And it's of mice who we're only eating the very worst part of the potato, as far as glycoalkaloids go. How often do you only eat the potato skin and literally nothing else in your diet? Nightshade avoidance has many historical precedents. Traditional Ayurvedic medicine in India warns against nightshades. Again, this may have roots in the fact that these foods are relatively new arrivals in. Afro-Eurasia, and that includes India. But in modern Western science, the earliest concerns about nightshades and inflammation that I can find were voiced by this guy, Dr. Norman Childers, a horticulture professor at Rutgers University who just passed away a couple of years ago. According to his own account, Childers developed arthritis and diverticulitis in the early 1970s.

He cut out all nightshades and his symptoms vanished. To his credit, Childers acknowledged that this was purely anecdotal. Inflammatory conditions naturally wax and wane all the time, so you really can't know if a change in your condition was caused by a change in your diet. But the experience prompted Childers to do some survey research. How did he get people to fill out his questionnaires? Well, he published books all about the evils of nightshades and included questionnaires that readers could send back. And if that isn't biasing subjects in your survey group, then I don't know what is. Anyway, Childers got a lot of survey responses back and surprise, surprise, lots of people in that group self-reported improvements in their symptoms when they cut out nightshades, including tomato, eggplant, and tobacco. Wait a minute — tobacco? Tobacco is a nightshade, and it's a nightshade that contains a toxic alkaloid, namely nicotine.

That's why smokeless tobacco products still aren't that great for you. Childers, in addition to all of his other highly-questionable survey methods, did not disaggregate between health improvements that might have been caused by cutting out tobacco versus health improvements that might have been caused by cutting out eggplant. It's all lumped under one category called nightshades. It's not exactly surprising to hear that people quit smoking and their health improved. And Childers himself acknowledged this problem with his data. Remember these surveys were done in the 1970s and '80s when tobacco use was way higher. So yeah, I think maybe smoking was the problem. Lots of the fringe sources that demonize nightshades cite Childers as their big scientific source.

And I'm sorry, but that's just nuts.

Some of the people who throw shade

On nightshades also cite this paper 2017 study out of california.

They had 18 human beings with inflammatory bowel disease do a six-week AIP diet, Autoimmune. Protocol Diet. This involves cutting out nightshades and grains and legumes and dairy and eggs and coffee and alcohol and nuts and seeds and refined/processed sugars, oils, and food additives. It's basically Paleo diet. And yeah, the 15 people who actually finished the diet showed some improvement in their inflammatory symptoms. Was it the nightshades that made the difference or was it the sugar or the booze? Sugar and booze have absolutely been shown in many studies to aggravate inflammatory conditions.

Meanwhile, we have studies like this 2002 experiment out of Sweden. They took people with rheumatoid arthritis and put them on the Mediterranean diet, which includes a lot of tomatoes and other nightshades, and those people saw significant improvement in their symptoms. Sure. Tomatoes have, Tomatine, a toxic alkaloid, but that's mostly in the stems and the leaves rather than the fruit. And they contain other compounds like lycopene that have been shown to have anti-inflammatory properties. Now, some people have been shown to be straight up allergic to compounds that are found in nightshades. And obviously, yeah, they shouldn't eat them. And the people at the Arthritis Foundation and similar sources, they acknowledge the anecdotal accounts of people who cut out nightshades and then showed some improvement in their symptoms.

Research in this area is ongoing, but there's nothing remotely conclusive yet. And remember, the open question is whether nightshades can aggravate existing inflammatory conditions in some people. I can find no credible scientific source claiming that nightshades cause inflammatory conditions. If you break your arm, your doctor will tell you to stop moving your arm until it heals. From that information, would you then extrapolate that it's better to never move your arm at all, even if your arm isn't broken? Eat nightshades. Night shades are plants, and plant foods are generally really good for you. Eat nightshades unless you have a particular reason to try not eating them. Nightshades are good...