Nightshade vegetables are thought to be harmful because they are often confused with the ‘deadly nightshade’, an inedible weed that’s also part of the Solanaceae family1. Historically, ‘deadly nightshade’ has been associated with witchcraft. When ingested in large amounts, it may cause convulsions or even death.
Contrary to popular belief, ‘deadly nightshade’ has nothing to do with edible nightshade vegetables like eggplants, peppers, potatoes, and tomatoes. These vegetables have been given a bad rap because celebrities like Gwyneth Paltrow and Kate Moss claim nightshades are related to poison ivy (potentially poisonous). But poison ivy isn’t even in the same plant family!
Nightshade vegetables have amazing nutrients like antioxidants, fiber, vitamins, and minerals. These nutrients are recommended as part of a healthy diet to reduce the risk of cancer, heart disease, and other degenerative diseases. For instance, tomatoes are full of lycopene, an antioxidant which is known to lower the risk of stroke2. Plus, it is a great source of vitamin A and C. Similarly, chili peppers are rich in the phytonutrient capsaicin, which promotes weight loss3.
Nightshade vegetable myths – what you need to know
Myth 1: Nightshade vegetables increase the risk of osteoporosis
Certain diet plans recommend avoiding nightshade vegetables because they believe they can cause osteoporosis. This thought came about because nightshade vegetables contain oxalic acid. Oxalic acid inhibits calcium absorption which can lead to osteoporosis. This is only possible when calcium intakes are deficient and oxalate intakes are very high. The truth is that nightshades are not high in oxalic acid and there is no scientific evidence for bone loss. To reduce the risk of osteoporosis, cut back on consuming too much sodium, refined sugar, animal protein, and caffeine. There is evidence that these foods increase the risk of osteoporosis.
Myth 2: Nightshade vegetables cause arthritis
One of the popular myths about nightshade vegetables is that they can cause arthritis. This is because they contain a compound called solanine. But there is no evidence that nightshade vegetables cause arthritis. A Rheumatologist from the Cleveland Clinic explains that it is very unlikely that avoiding nightshade vegetables (for trace amounts of solanine) will ease arthritis pain4. There is no reliable research to support this claim. Instead, he recommends limiting processed meat, fried foods, and refined carbohydrates to alleviate arthritis.
Myth 3: Nightshade vegetables cause migraines
There are no studies that link nightshade vegetables to migraine triggers. Director of Neurology Dr. Gladstone from Cleveland Clinic Canada states that there is no evidence that nightshades vegetables cause migraines.
Myth 4: Nightshade vegetables contain a toxic alkaloid
An alkaloid is a naturally occurring compound that is primarily found in potatoes. Green spots or new sprouts outside potato are signs of high alkaloid content. It is best to avoid such potatoes. For the record, eggplants, peppers, and tomatoes do not produce alkaloids and are safe to eat.
1. Scientific Opinion on Tropane alkaloids in food and feed, 15 October 2013
2. Lycopene-rich tomatoes linked to lower stroke risk, OCTOBER 10, 2012
3. Could capsaicinoids help to support weight management? A systematic review and meta-analysis of energy intake data, 2014 Feb;73:183-8. doi: 10.1016/j.appet.2013.11.005. Epub 2013 Nov 15
4. Arthritis: Should You Avoid Nightshade Vegetables?, June 14, 2018