Alkaloid compounds are found throughout the nightshade family; they’re part of the plants’ defense systems against insects, molds, and pests. Most of the roughly 2,500 nightshade species contain alkaloids and other compounds that are toxic to humans and other mammals if consumed in certain amounts.
Yet some nightshade alkaloids are used medicinally. The capsaicin in hot peppers, for instance, produces analgesic effects and is used in topical creams to soothe arthritic pain.
Research hasn’t definitively pinned down the mechanisms by which nightshades sometimes cause problems in some people. “But what you do find in the literature is that when some people remove them, they feel better,” says Susan Blum, MD, MPH, assistant clinical professor of preventive medicine at the Icahn School of Medicine at Mount Sinai and founder and director of Blum Center for Health in Rye Brook, N.Y.
If your immune system is healthy and you eat a wide variety of foods, toxic compounds including alkaloids don’t accumulate and don’t cause problems.
For example, in an observational study of people with psoriasis, researchers found that 52 percent of those who had reduced or stopped their nightshade consumption reported improvements in their skin. That said, the participants also eliminated other allergenic substances, such as gluten and dairy, so it’s difficult to isolate which of these changes produced the positive outcomes.
Importantly, nearly all the interventions used in the study aimed to heal the gut. “It looks like the mechanism by which alkaloids cause inflammation is via the gut,” Blum says. Some research suggests that these compounds disrupt cholesterol-containing membranes in the intestinal epithelium, the single-cell layer lining the intestines.
“All the foods we eat are a mixture of compounds that are helpful to us and things that are toxic to us,” notes Wahls. If your immune system is healthy and you eat a wide variety of foods, she adds, toxic compounds, including alkaloids, don’t accumulate and don’t cause problems.
But people whose immune systems are already dysregulated may be susceptible to the gut-irritating effects of alkaloids, says Blum. In predisposed individuals, nightshades may trigger joint pain or swelling; migraines, fatigue, or brain fog; skin issues, such as acne or hives; or GI issues, including diarrhea, gas, bloating, and nausea.
“When it comes to a patient with rheumatoid arthritis, I’m looking at what damaged the gut — was it antibiotics? Was it diet? Was it trauma, stress?” explains Blum. “It could be a tick bite when they were 13. I don’t think nightshades caused the problem, but they may be a secondary problem now.”
This was excerpted from “How to Navigate Nightshade Foods” which was published in the July/August 2022 issue of Experience Life.