What are Nightshades and Do They Cause Inflammation?
How to know if you’re sensitive to nightshades
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Ray recently asked me to weigh in on conflicting information he’s read about tomatoes, peppers, and other foods in the “nightshade” family:
“Many folks say that nightshades cause inflammation and should be avoided,” he writes, “but you recommend them as anti-inflammatory in your book, [The Inflammation-Free Diet Plan]. Can you clarify?”
The same week, I got an email from Jim, who wrote,
“I have been avoiding all nightshades for about 5 months now in an effort to clear up [an inflammatory condition] but I haven't really seen an improvement. I would love to return to eating green chiles and tomatoes.”
Let me see if I can clear up some of the confusion about nightshades and inflammation.
Spoiler Alert: Good news for you, Jim!
What Are Nightshades?
Tomatoes, peppers, potatoes, and eggplant (as well as tobacco) all belong to the same botanical family, commonly known as the nightshades. The Latin name for this family of plants is Solanaceae, because all of them produce an alkaloid compound called solanine. Solanine is part of these plants’ natural defense system, acting as a nerve poison on insects that try to eat the plants.
Is Solanine Toxic to Humans?
Obviously, it’s going to take a lot more solanine to cause problems for a human being than for a bug. And for most people, the amount of solanine you’d ingest by eating even large quantities of tomatoes and peppers isn't enough to cause any problems.
By the way – Solanine is concentrated in the leaves and stems, and that’s one of the reasons we don’t eat those parts of the plants. A big salad of tomato or potato leaves might actually contain enough solanine to give you an upset stomach. (And just in case you’re wondering, sweet potatoes are not in the nightshade family and that’s why we can enjoy sweet potato greens.)
Perhaps you’ve also heard that potatoes with sprouting eyes are poisonous. That’s because potatoes that have started to sprout or have developed a greenish tint to their skins are often higher in solanine. It’s best not to eat them.