The bottom line
Nightshades (tomatoes, potatoes, peppers) are useful to learn about if you have chronic pain. Why? It costs exactly zero dollars to eliminate them, and I’m absolutely sure that at least a few people will be surprised at this seemingly innocent class of plants being the cause of their pain.
That being said, nightshades aren’t often the main source of pain. And nightshade elimination diets are hard, due to how common potatoes / tomatoes / peppers are in typical diets. If you try this diet, you need at least 2-3 weeks of strict adherence in order to test your response.
What are nightshades?
The word “nightshade” sure sounds ominous, huh? Did you read about the 9-year old girl who died from eating nightshades?
I have a feeling the answer is no, but please don’t worry too much. She ate a few berries of something called Belladonna, or Deadly Nightshade. Plants that fall under the family of Nightshade (otherwise known by the fancy botanical name Solanacea ) though are some of the most widely eaten foods on earth. Tomatoes and potatoes are the most commonly eaten of the edible nightshades, but there are a few others. Note what is not on the list: sweet potatoes, black pepper, and white pepper are not nightshades. Finally, note the most famous of all nightshades, and destroyer of lungs worldwide: the tobacco plant!
How did this whole nightshade <–> pain connection get started?
Waaaaay back in the 1940s, a horticulturist named Norman Childers got the nightshade-pain ball rolling. He noticed that livestock who munched on nightshades had a tendency to develop arthritis. When these nightshade plants were taken away, the animals tended to have reduced arthritic symptoms. This phenomenon was noticed by others, namely veterinarians and botanists, but word didn’t really get out (Internet use was pretty low in the 1940s). More importantly, when Norman eliminated nightshades from his diet, his own arthritis was cured. The specific reasons why nightshades might be implicated in some cases of arthritis will be explained later.
But aren’t vegetables good for you?
Don’t fall into this trap: “Tomatoes are vegetables. Vegetables are good for you.” First of all, you may be aware that the tomato is botanically a fruit, but legally a vegetable. Second of all, believing that edible plants are all good for you is a very modern way of thinking. Back in the day, before agriculture started, you had to know which plants helped you and which plants harmed you. Nowadays, we all know which plants might hurt you, if you happen to be sensitive to them. The prototypical example is the ever increasing number of people with peanut allergies. But there are more bad plants than just the occasionally evil peanut and the occasionally trip-inducing mushroom. If you have a severe peanut allergy, you would know it because eating a peanut would lead to an anaphylactic shock and a trip to the ER. But there are many, many people who have reactions to plants that don’t happen right away, and hence are hard to tie directly to the plant.
What does the evidence say about nightshades and pain?
There are three possible ways nightshades could impact pain: vitamin D, the nervous system, and the gut.
1) Nightshades and Vitamin D
Dr. Childers blamed the arthritis-inducing tendencies of nightshades on its vitamin D content. I bet you’re a little confused…isn’t vitamin D supposed to be good for you? In fact, the first paper I co-authored was on “Vitamin D and Cardiometabolic Outcomes”. Being entrenched in academia, I was skeptical of Dr. Childers’ claims. I’m still a little skeptical, but the science is pretty legit. Here’s why.
Way back in 1976, a professor of biomedical sciences at Cornell University got a paper published in the prestigious journal “Science”. His lab found that a South American nightshade plant contained the active form of vitamin D! Other papers have backed up this finding.
This is surprising. Too much vitamin D can potentially screw with your calcium balance. And because of the potent form of vitamin D in this plant, it can cause calcium to deposit into the joints of animals that eat the leaves, causing pain and crippling arthritis. Is this the case with humans? Nobody knows. The mechanism is there, but we don’t share the same physiology as these animals, nor do we graze on leaves in South America. On the other hand, calcification is a big freaking deal. One of the best predictors of getting a heart attack is a high coronary calcium score. You don’t want calcium to be going where it doesn’t belong! If you are concerned about calcification, consider getting more vitamin K2 to help counter it, which is found in cheese, grass-fed butter, natto, and some supplements.
2) Nighshades and your nervous system
Your nerves use certain chemicals to communicate with each other and with your brain. If something bad happens to this communication system, things can go wrong with many different things in your body. One of these chemicals is called acetylcholine, and certain chemicals in nightshades can screw up how acetylcholine gets used in the space between nerve endings.
How does this happen? Nightshades contain a variety of chemicals called glycoalkaloids, which are substances used by these plants to scare away animals that want to eat them. Pretty much like human-made pesticides, but naturally made. But natural is not always good! These natural pesticides, such as solanine and tomatine, can irritate your intestines and cause a variety of other problems by affecting acetylcholine. Thankfully, the majority of these substances are found in parts of the plant we don’t eat, such as the leaves. You don’t eat tomato leaves regularly, do you? Good.
Study #1: Arthritis, fibromyalgia, and the immune system
One study from 1998 looked at the relationship of food sensitivities to joint and muscle pain. It looked at how pain patients reacted to antigens from certain foods. What are antigens? Antigens are simply molecules that make your body mount an immune reaction.
The theory that this paper was based on is that antigens from some foods can leak through your intestine and cause joints and/or muscles to be attacked by your own immune system. Intestines can become leaky because of wide variety of things, including overuse of some medications and a diet high in gut-attacking foods. The authors found that between 56-67% of patients at their clinic who had pain issues were reactive to antigens from various nightshade plants. When patients were tested against antigens from several different foods, fibromyalgia patients had the highest rate of reactivity, followed by arthritic patients and then back pain patients. The study authors concluded that they found “a high correlation between food sensitivities and musculoskeletal disease”.
My take from this study: it doesn’t really mean anything, and is not a very high quality study because of poor study design, few patients, and lack of detail. So while we may note with interest that there may be something to nightshade antigens and reactions in pain patients, we can’t really draw any conclusions from this paper.
Study #2: Dr. Childers’ report
Dr. Childers made it his mission to help those whose arthritis is caused by nightshades. As part of this effort, he surveyed volunteers to see if they had stopped eating nightshades and seen a decrease in pain. Most of the respondants (94 percent!!) were substantially helped by a nightshade-free diet, when they were rigid with following it. About two thirds had relief when mostly complying with the diet.
Unfortunately, this is another poor quality study. Dr. Childers did not make any claims as to the certainty of this data, which is good. Because this was simply a survey of volunteers who bought a book about nightshades and arthritis. One reason you might buy such a book is if you suspect that nightshades might be causing your pain. While you’re eliminating nighshades from your diet, you might do other things such as lose weight, or even just improve your symptoms from the time you started the book until the time you ended the book. So in summary, this is not a trial; and without a trial, it is hard to make any conclusions about the link between nighshades and pain in humans.
Should you think about eliminating nightshades?
So…are nightshades the cause of your pain? Probably not. But ten billion things can cause pain, so nothing is ALWAYS the culprit. The question is whether it is worth it for you to try an elimination diet. The answer is…definitely! Depending on who you are. No reliable lab test can predict if you are sensitive to nightshades. Those who are under high stress, have previously-injured joints, or have a genetic susceptibility to nerve issues should watch out. Here are some categories of people with pain, and my suggestions for them:
1. Longtime arthritis sufferer
Try a nightshade elimination diet. Just do it. It might do absolutely nothing, but you also don’t want to be taking pharmaceutical drugs with harmful side effects your whole life. Also, arthritis wears down joints over time, and you don’t want to be amongst the millions of Americans getting multiple replacement joints.
2. Sports injury
It might not be worth it. If you haven’t experienced pain before, and have an injury of moderate duration (a week to a couple months), the pain is probably not from nightshades.
Try the diet! Not necessarily because nightshades are causing your pain, but because fibro is caused by so many strange things. But try to attack this from multiple angles–do some reading on fibro and massage, fibro and vitamin D, etc etc.
4. Autoimmune disease
Do you have an autoimmune disease? Then think about trying a nightshade elimination, getting your vitamin D level checked by your doctor, and eliminating wheat from your diet. There’s a lot of things to consider in autoimmune disease, and these are just some of them. But there’s no time like the present to become your own Sherlock Holmes, and potentially solve your own illness.