Several common foods contain small amounts of nicotine, most of them from the same botanical family as tobacco. Tomatoes, peppers, potatoes, and eggplant all belong to the nightshade family (Solanaceae) and naturally produce the compound, though at concentrations thousands of times lower than what you’d find in a cigarette. Tea leaves also contain detectable nicotine, and the story of how scientists figured out whether that nicotine was natural or a residue from pesticides is more interesting than you might expect.
The Nightshade Vegetables
Tobacco is a nightshade, and it turns out its botanical relatives share its signature chemical, just in far smaller doses. The four everyday nightshade vegetables that have been analyzed most thoroughly are tomatoes, peppers (both sweet and hot), potatoes, and eggplant (also called aubergine). One widely cited analysis found fresh nightshade vegetables contained nicotine in the range of roughly 2 to 7 micrograms per kilogram of fresh weight.1PubMed. Determination of the nicotine content of various edible nightshades (Solanaceae) and their products and estimation of the associated dietary nicotine intake That is an extraordinarily tiny amount. To put it in perspective, a single cigarette delivers roughly 1,000 to 2,000 micrograms of nicotine into a smoker’s bloodstream. You would need to eat many kilograms of raw tomatoes in a single sitting to approach the nicotine dose of one puff.
A later study that compiled multiple published measurements reported somewhat higher median values, particularly for peppers and tomatoes. In that compilation, peppers came in highest among nightshade vegetables at a median of about 102 micrograms per kilogram, fresh ripe tomatoes at roughly 44 micrograms per kilogram, processed tomato products (like juice or paste) at about 30 micrograms per kilogram, and cooked potatoes at around 19 micrograms per kilogram.2PubMed Central. Nicotine from edible Solanaceae and risk of Parkinson disease Eggplant, often cited in popular articles as a nicotine-containing food, actually had nicotine levels below the limit the instruments could reliably measure in that same dataset. So while eggplant does contain some nicotine, it appears to have less than the other nightshades people commonly eat.
The discrepancy between the two sets of numbers, 2 to 7 micrograms per kilogram versus the higher medians in the later compilation, reflects real variability. Nicotine concentrations in any given vegetable depend on variety, ripeness, growing conditions, and how the food is prepared. A green tomato has more nicotine than a ripe red one. A raw potato has a different profile than one that has been boiled. Measurements also depend on the sensitivity of the analytical method used, and techniques have improved over the decades. The point remains the same either way: the amounts are extremely small compared to tobacco.
Tea Leaves
Nicotine in tea has a more complicated backstory than nicotine in tomatoes. When researchers in the late 1980s detected nicotine in green and instant tea at levels of 2 to 23 parts per million, they suspected it was contamination from nicotine-based insecticides, which were widely used in agriculture at the time.3Journal of Food Science. Detection of Nicotine in Foods and Plant Materials That explanation seemed reasonable, since tea plants are not nightshades and had no obvious evolutionary reason to produce nicotine.
Decades later, a more thorough investigation settled the question. Researchers collected tea samples from tea-growing regions across six Asian countries and analyzed them using modern mass spectrometry. Every single sample contained nicotine, at levels ranging from 0.011 to 0.694 micrograms per gram of dry leaf. The nicotine content held steady through the manufacturing processes for green, oolong, and black teas, meaning it survived heating, drying, enzymatic oxidation, and mechanical damage. Different cultivars had different levels, with a black tea cultivar called Benifuki showing higher nicotine than the others tested.4PubMed Central. Quantitative validation of nicotine production in tea (Camellia sinensis L.) The consistency across regions and the stability through processing both pointed to the same conclusion: tea plants genuinely make their own nicotine. It is not just a residue from spraying.
How much nicotine ends up in your cup is harder to pin down, because steeping extracts only a fraction of what is in the dry leaf. But the total amount is vanishingly small compared to tobacco. The finding is more interesting for what it says about plant biology and pesticide analysis than for any health concern about your morning tea.
Why These Plants Make Nicotine at All
Nicotine is not a waste product or an accident. It is a weapon. Plants cannot run from the insects that eat them, so many species produce chemical defenses instead. Nicotine is one of the most studied examples. It is toxic to insects because it overstimulates their nervous systems, and plants that produce more of it tend to lose less leaf tissue to hungry bugs.
This has been demonstrated directly in field experiments. When researchers genetically engineered native tobacco plants to produce much less nicotine than normal and then planted them alongside unmodified plants in the wild, the low-nicotine plants lost more than double the leaf area to herbivores over a 16-day period.5PLOS Biology. Nicotine’s Defensive Function in Nature Insects preferred eating the low-nicotine plants and performed better on them, confirming that nicotine acts as a genuine defensive chemical in nature.
This defense function helps explain why nicotine shows up in nightshade vegetables and tea. The compound evolved as part of a broad chemical defense strategy. Tobacco produces enormous quantities of it because tobacco faces heavy insect pressure and has invested heavily in that particular defense. Its vegetable relatives produce far less, likely because they rely on other defensive strategies as well, or because human breeding over centuries has selected for taste and yield rather than insect resistance. In tobacco, the amount of nicotine a plant produces is strongly influenced by nitrogen availability in the soil, since nitrogen is a building block of the nicotine molecule. More nitrogen means more nicotine.6Agronomy Journal. Agronomic Practices Affecting Nicotine Concentration in Flue‐Cured Tobacco: A Review The same basic chemistry applies to other nicotine-producing plants, which is why growing conditions affect the nicotine levels researchers measure in vegetables.
How Dietary Nicotine Compares to Tobacco
The gap between dietary nicotine and tobacco nicotine is so large that comparisons almost feel silly, but the numbers are useful for clearing up misconceptions. One estimate based on food consumption data calculated that the average person’s daily nicotine intake from food is about 1.4 micrograms, with people at the high end of vegetable consumption taking in roughly 2.25 micrograms per day.7Food Chemistry. The contribution of dietary nicotine and dietary cotinine to salivary cotinine levels as a nicotine biomarker A single cigarette delivers somewhere around 1,000 to 2,000 micrograms. So even a heavy vegetable eater gets roughly a thousandth of the nicotine from food that a smoker gets from one cigarette.
This means dietary nicotine is not pharmacologically active in any meaningful sense. The amount is too small to bind to receptors in the brain in the way that inhaled nicotine does, and far too small to produce dependence, pleasure, or any of the other effects people associate with nicotine use. You cannot get a buzz from eating peppers, and you cannot develop a nicotine habit from tomato sauce, no matter how much you eat.
Can Eating Nightshades Affect a Cotinine Test?
When your body processes nicotine, it converts most of it into a metabolite called cotinine, which lingers in blood, saliva, and urine for longer than nicotine itself. Cotinine tests are widely used to check whether someone has been using tobacco or has been exposed to secondhand smoke. This raises a fair question: could eating a lot of tomatoes or peppers produce enough cotinine to trigger a positive test?
The concern is not completely unfounded. An early analysis calculated that dietary nicotine could theoretically produce urinary cotinine concentrations in the range of 0.6 to 6.2 nanograms per milliliter, depending on assumptions about how much nightshade food a person eats.8PubMed. Dietary nicotine: a source of urinary cotinine Those values are low but not zero, and the study’s authors raised the possibility that dietary nicotine could complicate cotinine-based estimates of secondhand smoke exposure.
However, follow-up work using more precise measurements and actual dietary data reached a less alarming conclusion. When researchers modeled typical food intake, the predicted salivary cotinine from dietary nicotine came out to about 0.022 nanograms per milliliter, a level too low to meaningfully interfere with tobacco exposure assessments.7Food Chemistry. The contribution of dietary nicotine and dietary cotinine to salivary cotinine levels as a nicotine biomarker For context, active smokers typically have cotinine levels hundreds or thousands of times higher, and even most secondhand smoke exposure produces cotinine well above what food could generate. So while the theoretical concern exists, in practice your salad is not going to make you test positive for smoking.
The edge case worth mentioning involves extremely sensitive research settings. In studies trying to distinguish very low levels of secondhand smoke exposure from no exposure at all, the tiny cotinine contribution from diet could in theory matter. But for the kinds of cotinine tests used by employers, insurance companies, or doctors, dietary nicotine is a non-issue.
Foods People Ask About That Do Not Actually Contain Nicotine
Once word gets out that “vegetables contain nicotine,” the claim tends to grow in the retelling. Cauliflower and broccoli are sometimes listed on popular health sites as nicotine-containing foods. These are cruciferous vegetables, members of the Brassicaceae family, not nightshades. While trace amounts of nicotine have occasionally been detected in various non-nightshade produce, those detections are not consistent, and the levels are even more vanishingly small than in tomatoes. Some of those detections may reflect contamination from soil, from nearby tobacco fields, or from nicotine-based pesticides rather than endogenous production by the plant. The nightshade vegetables and tea are the foods where endogenous nicotine production has been convincingly demonstrated.
Similarly, you may encounter claims that certain spices or herbs contain nicotine. Many plants produce other alkaloids that are chemically related to nicotine but are not nicotine itself. The distinction matters because different alkaloids have different biological effects. Just because a compound is structurally similar to nicotine does not mean it activates the same receptors or poses the same concerns.
The Parkinson’s Disease Connection
One reason scientists have bothered to measure nicotine in vegetables at all is the long-standing epidemiological observation that tobacco users get Parkinson’s disease at lower rates than non-users. Whether nicotine itself is responsible for this association, or whether other compounds in tobacco or even personality traits linked to smoking are the real explanation, has been debated for decades. The finding that nightshade vegetables also contain nicotine offered a way to test the hypothesis without the massive confound of smoking.
The study that compiled those median nicotine values for peppers, tomatoes, and potatoes was actually a case-control study of Parkinson’s disease risk.2PubMed Central. Nicotine from edible Solanaceae and risk of Parkinson disease The researchers were not primarily interested in food chemistry; they wanted to know whether eating more nightshade vegetables was associated with lower Parkinson’s risk, which would strengthen the argument that nicotine specifically has a protective effect on dopamine-producing neurons. That study found some evidence of such an association, particularly for peppers, though the research in this area is still evolving and the effect sizes are modest.
This line of research is worth knowing about because it reframes the conversation around dietary nicotine. Rather than being a contaminant or a curiosity, the trace nicotine in your food might have a small biological significance that researchers are still working to understand. It is far too early to recommend eating extra peppers as a Parkinson’s prevention strategy, but the hypothesis is scientifically legitimate and continues to attract research attention.
Cooking, Processing, and What Happens to the Nicotine
If you are curious whether cooking destroys the nicotine in your vegetables, the answer is: partly, but it depends on the method. Boiling potatoes, for instance, leaches water-soluble compounds including nicotine into the cooking water, which most people discard. Frying or roasting at high temperatures can degrade some alkaloids. But nicotine is relatively heat-stable, which is why it survives the curing and processing of tobacco leaves, and why it persists through the manufacture of tea. The nicotine values reported for “cooked potatoes” in the research are lower than those for raw potatoes, but some nicotine remains.2PubMed Central. Nicotine from edible Solanaceae and risk of Parkinson disease
Processed tomato products like ketchup, canned sauce, and tomato paste are concentrated forms of tomato, so you might expect them to have more nicotine per serving than a fresh tomato. The data bear this out to a degree, with processed tomato products showing a median of about 30 micrograms per kilogram. But the amounts still remain trivially small in the context of overall dietary intake. Nobody needs to rethink their pasta sauce.
For tea, the stability finding is clear: nicotine levels stay essentially constant whether the tea is green, oolong, or black, despite the very different processing each type undergoes.4PubMed Central. Quantitative validation of nicotine production in tea (Camellia sinensis L.) The heating, rolling, and oxidation steps of tea production do not break nicotine down. What varies between teas is the cultivar, not the processing method.
How Growing Conditions Change the Numbers
One reason published nicotine values for vegetables span a wide range is that the same species of plant can produce very different amounts of nicotine depending on how and where it is grown. In tobacco farming, this is well understood and actively managed. Nitrogen fertilization is the single biggest lever: since nitrogen is a core component of the nicotine molecule, plants with access to more soil nitrogen produce more nicotine.6Agronomy Journal. Agronomic Practices Affecting Nicotine Concentration in Flue‐Cured Tobacco: A Review Planting density also matters. In denser fields, individual tobacco plants produce less nicotine, likely because competition for light and nutrients shifts the plant’s resource allocation.
The same principles apply in a general sense to nightshade vegetables, though the research on fine-tuning nicotine in food crops is far less extensive than for tobacco. Soil composition, water stress, insect pressure, and even the specific cultivar all influence how much nicotine a tomato or pepper ends up containing. This is why a study analyzing peppers from one region might report numbers that look quite different from a study conducted elsewhere. It does not mean the measurements are wrong; it means plant chemistry is more variable than a single number can capture.
For the curious home gardener, there is no practical way to control or measure the nicotine in your tomatoes, and no reason to try. The variation matters for researchers designing studies and for regulators setting pesticide residue limits (since endogenous nicotine can be mistaken for pesticide residue), but it is irrelevant to anyone simply eating vegetables as part of a normal diet.