There’s nothing like the comforting goodness of a bowl of mashed potatoes or a not-so-healthy side of salted french fries. The white potatoe is one delicious vegetable that doesn’t disappoint fried and diced or mashed and boiled. However, it’s part of the family of nightshade vegetables which have, unfortunately, gotten a pretty bad rap over the years.
Nightshade vegetables have been reported to cause migraines, inflammation, osteoporosis and a whole host of other health problems. While it’s true that nightshades contain an alkaloid called solanine, which is toxic in high concentrations, most species commonly cultivated for human consumption contain only trace amounts — if any — so they are safe.
The term nightshade encompasses a large group of foods, herbs and trees — so when you’re thinking of nightshades, you’re not just talking about edible food. In fact, nightshades include more than 2,800 species of plants, such as white potatoes (not sweet), tomatoes, hot peppers, bell peppers and eggplants.
Nightshade vegetables are extremely healthy and — for most people — perfectly tolerable. Eat up because they contain many health benefits such as vitamins, minerals, antioxidants and fiber. Now let’s dive into the misinformation surrounding nightshades.
Do nightshade vegetables cause migraines?
There is not sufficient research to support a causal link between nightshade vegetable consumption and migraines. A lot of the claims about the harmful effects of nightshades are anecdotal and highly individualized. Migraines can be caused by a wide range of factors and underlying conditions that should be taken into consideration before engaging in an elimination diet.
Do nightshade vegetables cause inflammation?
There have not been large scale studies that link nightshade vegetables to inflammation. There are anecdotal claims that link nightshades to inflammation, but usually it is a case where there is inflammation due to an underlying condition. Nightshades can potentially add to that. It may be more beneficial to treat the underlying cause of inflammation (such as arthritis or lupus) before turning to an elimination diet for treatment. If you have an inflammatory condition and feel that nightshades are worsening your inflammation, talk to your healthcare provider.
Do nightshade vegetables prevent absorption of calcium leading to degenerative diseases, such as osteoporosis?
No evidence suggests a direct correlation between nightshade consumption and osteoporosis. The supposed link between nightshades and osteoporosis is that nightshades have oxalic acid which binds to calcium when consumed at the same time, blocking the absorption of calcium. However, nightshades are not high in oxalic acid; therefore, there is not sufficient evidence for this claim. Contrary to this claim, nightshades contain alkali compounds that can neutralize blood acid and protect bone health.
Do many people have nightshade vegetable intolerance?
Food intolerances are highly individualized and are often the result of a pre-existing or underlying condition and not the food itself. Many elimination diets are growing in popularity and the media can lead us to think these diets are appropriate or even recommended for a large range of people, when in fact, they are not. Always talk to your dietitian or primary care provider if you suspect an intolerance and would like to follow an elimination diet.
To test tolerance, remove the nightshades from the diet for a couple weeks and track symptoms. Even if it is determined that nightshades should be removed, it is possible to assess the underlying cause of inflammation with your provider and slowly work nightshades into the diet to improve tolerance.
Should people eat nightshade vegetables infrequently or mostly avoid them?
Nightshades contain a lot of beneficial vitamins and minerals and if there is no intolerance present, there is no reason to avoid them. For example, bell peppers are a great source of vitamin C, tomatoes are a great source of lycopene and eggplants contain calcium.
If you need to avoid nightshades due to an intolerance, you should make sure to select other foods that are good sources of the vitamins and minerals you would get through nightshade vegetables. (This is a good rule of thumb for any elimination diet: make sure you still get the vitamins and minerals you cut out through avoiding certain types of foods in other whole food sources!)
Mahan LK, Raymond JL. Elimination Diets. Krause’s Food & The Nutrition Care Process. St. Louis, Missouri: Elsevier;2017:796-797.
Harrison C, Breeding Z. “Nightshade Vegetables” + Inflammation. Pennsylvania Academy of Nutrition and Dietetics. 2017. https://eatrightpa.org/members/blog/nightshade-vegetables-inflammation/. Accessed February 24, 2021.