Yes, the potato is a nightshade. It belongs to the family Solanaceae, the same botanical family as tomatoes, eggplants, peppers, and tobacco. The USDA classifies the common potato under the genus Solanum, which literally translates to “nightshade.” Its full scientific name is Solanum tuberosum.
That classification raises questions for a lot of people, especially anyone who has heard that nightshades cause inflammation or should be avoided. Here’s what actually matters about potatoes being nightshades, from the compounds they contain to whether you need to worry.
What Makes a Plant a Nightshade
The Solanaceae family includes over 2,000 species, and the ones you’ll find in a grocery store are potatoes, tomatoes, bell peppers, chili peppers, eggplant, and tomatillos. What they share is a tendency to produce alkaloid compounds, specifically glycoalkaloids, as a natural defense against insects and disease. In potatoes, the two main glycoalkaloids are alpha-solanine and alpha-chaconine.
One common point of confusion: sweet potatoes are not nightshades. Despite the shared name, sweet potatoes belong to the morning glory family (Convolvulaceae) and are only distantly related to white potatoes. If you’re avoiding nightshades for dietary reasons, sweet potatoes don’t need to come off your plate.
Glycoalkaloids in Potatoes
A normal, healthy potato contains relatively low levels of glycoalkaloids, typically between 2 and 15 mg per 100 grams of fresh tuber. The USDA guideline considers concentrations above 20 mg per 100 grams unsafe, and the German Federal Institute for Risk Assessment recommends that table potatoes stay below 10 mg per 100 grams (100 mg per kg). There are no binding regulations in the United States mandating specific solanine limits, but commercial potato varieties are bred to stay well below the safety threshold.
The glycoalkaloids concentrate heavily in the skin. One study of potatoes sold in Jordan found that while whole tubers averaged about 19.5 mg per 100 grams, the skins alone ranged from 25.8 to 128 mg per 100 grams, with an average of 67.7. That’s why the peel matters more than the flesh when it comes to these compounds.
Why Green and Sprouted Potatoes Are Different
When potatoes turn green from light exposure or start sprouting, their glycoalkaloid levels spike. The green color itself comes from chlorophyll, which is harmless, but it signals that the potato has been exposed to conditions that also trigger solanine and chaconine production. At high enough concentrations, these compounds are genuinely toxic. Based on available human data reviewed by the WHO, an intake of 1 to 3 mg of total glycoalkaloids per kilogram of body weight is considered a toxic dose, and 3 to 6 mg per kilogram is potentially lethal.
For a 70 kg (154 lb) person, that toxic range starts around 70 mg of total glycoalkaloids. You’d have to eat a large quantity of normal potatoes to reach that level, but a few servings of heavily greened potatoes could get you there. The practical rule: if a potato has significant green coloring beneath the skin or extensive sprouting, discard it rather than trying to cut away the affected parts.
Does Cooking Reduce Glycoalkaloids
Not as much as you might hope. Boiling and microwaving whole, unpeeled potatoes have a negligible effect on glycoalkaloid content. Boiling peeled potatoes does better, reducing levels by about 39% as the compounds leach into the cooking water. Frying at typical temperatures (150°C to 180°C) causes little change, but frying at 210°C (410°F) results in roughly a 40% reduction.
Peeling is the single most effective step. Since glycoalkaloids concentrate in and just beneath the skin, removing it before cooking eliminates a large portion of the total content. For most people eating standard grocery store potatoes, this is more than sufficient to keep exposure well within safe ranges.
Nightshades, Gut Health, and Inflammation
The reason nightshades get flagged in certain dietary circles is their alkaloid and lectin content. Alkaloids can, in theory, damage the cells lining the intestinal tract, potentially contributing to increased intestinal permeability (sometimes called “leaky gut”). Lectins, another class of plant proteins found in nightshades, can interact with cell membranes and may increase their permeability in some cases.
This is the rationale behind elimination protocols like the Autoimmune Protocol (AIP) diet, which removes all nightshades, including potatoes, on the premise that lectins and alkaloids drive inflammation in people with autoimmune conditions. The idea is to strip the diet down, then reintroduce foods one at a time to identify personal triggers.
For the general population, the evidence that nightshades cause meaningful inflammation is thin. Potatoes are a significant source of potassium, vitamin C, and fiber, and most people tolerate them without any issue. The concern is more relevant for individuals with existing autoimmune or inflammatory bowel conditions who notice a pattern of symptoms after eating nightshade-heavy meals. If that describes you, a structured elimination trial is the most reliable way to figure out whether potatoes are personally problematic, since there’s no blood test or biomarker that diagnoses nightshade sensitivity.
Signs of Nightshade Sensitivity
There’s no universally agreed-upon diagnostic criteria for nightshade sensitivity, but the symptoms people most commonly report are digestive: bloating, gas, cramping, or diarrhea after eating potatoes, tomatoes, or peppers. Some people also report joint stiffness or increased joint pain, though the mechanism linking nightshade consumption to joint symptoms is not well established in controlled studies. The proposed pathway involves alkaloids increasing intestinal permeability, which could allow partially digested proteins into the bloodstream and trigger an immune response. Whether this happens at the glycoalkaloid levels found in a normal serving of potatoes is unclear.
If you suspect a sensitivity, removing all nightshades for 3 to 4 weeks and then reintroducing them one at a time gives you the clearest signal. Potatoes, tomatoes, and peppers should each be tested separately, since reacting to one doesn’t necessarily mean you’ll react to all of them.