Nightshade vegetables have long gotten a bad rap for aggravating chronic health problems, including arthritis. It’s claimed that eating these foods can cause joint swelling, pain and stiffness.
Nightshade vegetables (and fruits) belong to the Solanaceae plant family which contains roughly 2,700 species, most of them inedible. The edible ones include bell peppers, chili peppers, eggplant, tomatoes, tomatillos and potatoes.
But before you discard these nutritious foods from your diet, here’s what you need to know.
Do nightshades inflame?
The concern with nightshades revolves around alkaloids, naturally-occurring compounds in the leaves and stems that act as natural insect repellents. Alkaloids include solanine (found in potatoes, especially ones that have turned green), capsaicin (the chemical that gives chili peppers their heat) and nicotine.
The theory goes that alkaloids in nightshade vegetables promote inflammation and worsen symptoms in people with autoimmune inflammatory disorders such as rheumatoid arthritis, psoriasis and inflammatory bowel disease (e.g., ulcerative colitis, Crohn’s disease).
Yet, there is no scientific evidence to prove, even strongly suggest, that eating nightshade vegetables has a direct impact on arthritis symptoms. The research is lacking.
The idea that nightshades inflame joints comes from surveys of people who have arthritis and patient testimonials.
What’s more, the amount of alkaloids in edible nightshades is very low to begin with. (The exception is green potatoes; when exposed to light potatoes produce solanine as well as the green pigment chlorophyll.)
As well, cooking further reduces the alkaloid content of nightshade vegetables.
Still, it is possible that some people are affected by nightshades. Studies in mice, while limited, have suggested a link between alkaloids and inflammation.
In mice with inflammatory bowel disease, alkaloids were found to increase intestinal permeability, or leaky gut, as well as inflammation. Increased intestinal permeability means that bacteria could seep through the intestinal lining and enter the bloodstream, triggering inflammation.
How to know if you’re sensitive
If you think that eating nightshade vegetables exacerbates your arthritis symptoms, eliminate them from your diet for four weeks. Keep a diary to track your food intake along with changes in the frequency and severity of symptoms.
After one month, add these foods back to your diet. If doing so increases your symptoms, you may be sensitive to nightshades. Consider other factors, too, which can make rheumatoid arthritis worse such as stress and fatigue.
Nightshade vegetables are excellent sources of nutrients that help dampen inflammation in the body, including fibre, vitamin C and beta-carotene. If you decide to avoid nightshades, replace them with other foods that supply these nutrients.
Sweet bell peppers, for example, are outstanding sources of vitamin C. Others include strawberries, kiwifruit, cantaloupe, citrus fruit, brussels sprouts, broccoli, cabbage and cauliflower.
Switch white potatoes for vegetables that are high in fibre and beta-carotene such as sweet potatoes, butternut squash and carrots. Leafy greens like spinach, kale, Swiss chard and dandelion greens are also excellent sources of beta-carotene.
Like white potatoes, these vegetables also deliver plenty of potassium, a mineral that helps regulate blood pressure, nerve impulses and muscle contractions.
Eggplant is loaded with anthocyanins, potent anti-inflammatory phytochemicals. You’ll also find anthocyanins in blueberries, blackberries, strawberries, red grapes and beets.
Tomatoes, rich in vitamin C, are one of the top food sources of lycopene, a phytochemical with strong antioxidant and anti-inflammatory properties. Pink grapefruit and watermelon supply decent amounts, too.
If you're not a fan of tomato sauce, toss pasta with pesto sauce made with basil or parsley, herbs packed with anti-inflammatory compounds.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.