How much nicotine is in tea and vegetables

Question

Compared to a cigarettes, how much nicotine is in tea, coco powder and vegetables like tomatoes and potatoes?

For example, for a normal sized tomato, how many grams of nicotine is present?

Answer 1

Not much. Unless your vegetables or teas do contain tobacco or some exotic weeds.

In the letter mentioned in the comments was an interesting table listing different plant sources of nicotine. The highest amount was reported for eggplant containing 100ng/g of nicotine. In that letter this was translated into 10g of plant material needed for a consumer to ingest 1 µg of nicotine. These values were used because this level of exposure was deemed equivalent with the amount of nicotine obtained by a passive indoor smoker. An average cigarette contains around 10mg nicotine. (Take note of the different units of measurement.)

That would mean an unhealthy amount of vegetable is needed to be eaten to approach the nicotine levels of just one cigarette for a smoker.

Although this should have been clear from the start given the different magnitudes this letter provoked quite some reactions:

The main problem with the inferences in these authors' letter is a 500-fold error in the calculations used to determine the vegetable equivalent of toxicologically meaningful exposure to tobacco smoke.
Determining the amount of vegetable consumption suggestive of exposure to cigarette smoke is also more complicated and physiologically difficult than implied by Domino et al.
First, it would take an approximately 500-fold increase in the amount of vegetables estimated by Domino et al. to produce exposure equivalent to half a cigarette a day -- e.g., more than 100 kg of tomatoes would have to be consumed in one day.
Second, as acknowledged by Domino et al., nicotine exposure would be greatly reduced if vegetable skins, which contain most of the nicotine, were not eaten or if they were cooked in water, thereby extracting the nicotine.
Third, ingesting nicotine is not equivalent to inhaling it, since absorption from the stomach is poor and 70 percent of the nicotine entering the circulation is metabolized during its first pass through the liver.
Finally, it has been well confirmed that the exposure to tobacco smoke indicated by a plasma concentration of 5 to 10 ng of cotinine per milliliter is of clear toxicologic importance,3 whereas there is no evidence that daily exposure to the equivalent of 1 percent of the smoke from one puff of a cigarette would be of toxicologic importance or could possibly confound assessment of environmental exposure.[formatting and emphasis added]

To which the original author responded:

The amount of nicotine in certain vegetables is obviously too small to produce any pharmacologic or toxicologic effects. The difference between the small amount of nicotine in certain vegetables and the large amount in one average tobacco cigarette offers a marvelous lesson, both pharmacologic and toxicologic, on the importance of dose-effect relations. We never intended to suggest that vegetarians could become nicotine addicts, or that children who hate vegetables have a legitimate reason for refusing to eat them.

Many plants, only especially those of the nightshade family, contain chemicals that are classified as active drugs; like nicotine. But tobacco is specifically breed for nicotine content and cigarettes are standardised for its content.

Determination of the Nicotine Content of Various Edible Nightshades (Solanaceae) and Their Products and Estimation of the Associated Dietary Nicotine Intake:

Aubergines. Aubergines were investigated by Castro and Monji (1986), Sheen (1988), and Davis et al. (1991) with inconsistent results. The concentrations published previously include not detectable (Davis et al., 1991), >100 μg kg-1 wet weight (Castro and Monji, 1986), and 2.65 mg kg-1 dry weight (Sheen, 1988). We investigated four different types of aubergines, and nicotine could only be quantified in one sample. In two of the remaining samples, nicotine was detected but could not be quantified. […]
Tea. Conflicting results are found in the literature concerning nicotine concentrations in black tea (Sheen, 1998; Davis et al., 1991; Domino et al., 1993). Therefore, tea samples were analyzed for nicotine to address these contradictory results. The concentrations that were found in the dry tea leaves (Table 6) were surprisingly high in concentration, ranging from 163 to 1600 μg kg-1. Large variations were found within the types of black tea, whereas the concentrations were more or less consistent within the green teas. For an estimation of the dietary nicotine intake from tea, the nicotine concentration of the tea leaves is less relevant than that in brewed tea. Tea was brewed using common amounts of tea leaves and water. The results show that nicotine is not efficiently extracted by conventional brewing techniques (Table 7). Even tea with very high nicotine concentrations in the leaves (e.g., teas 3 and 4) do not show high amounts in the brewed tea. If detectable, the extraction yield is in a range of 20-25%.

Averaged Nicotine Concentrations 
  Based on the Observed Nicotine Concentrations
source                       nicotine (ng/g)  SD (ng/g)
nicotine from potatoes       4.5              1.9
nicotine from tomatoes       2.7              0.7
nicotine from tomato paste   5.3              0.6
nicotine from tomato sauce   4.5              1.5
nicotine from ketchup        7.3              1.5
nicotine from aubergine      2.1              0.5
nicotine from brewed tea     4.0              0.3

The edible Solanaceae analyzed in this investigation were found to contain relatively consistent amounts of nicotine in the range of 2-7 μg/kg for fresh fruits. These results are in agreement with most but not all of the previous results reported in the literature. Nicotine appears to survive a variety of processing operations such as the preparation of tomato ketchup, sauces, and pastes as well as frying and boiling of potatoes. These products showed slightly higher concentrations in comparison to the related fresh fruits. Relatively large concentrations of nicotine found in tea leaves were not reflected in brewed tea. Using food consumption data from government sources, a mean estimated daily dietary intake of nicotine is approximately 1.4 and 2.25 μg/day at the 95th percentile based on the nicotine content and consumption data discussed in this report. It is possible that these estimates are low because of incomplete food consumption data. Further work is required to relate the estimated dietary nicotine intake to nicotine metabolite concentrations in biological fluids to be able to make reliable statements about the importance of dietary nicotine intake in comparison to environmental tobacco smoke exposure.

To bring that back into perspective, a reminder on SI units of magnitude seems appropriate:

10⁻³g = mg = milligram
10⁻⁶g = µg = microgram
10⁻⁹g = ng = nanogram

And:

Nicotine is the principal alkaloid in commercial tobacco, N. tabacum, usually accounting for >90% of the alkaloid fraction whereas nornicotine, anabasine, and anatabine seldom accumulate to >5%. Further nicotinoids are present only in very small concentrations in tobacco (Bush et al. 1999).[…]
Nicotinoid Content of Cured Tobacco Leaves and Tobacco Smoke. Of course there are differences concerning the qualitative alkaloid profile of green tobacco leaves, cured leaves, and tobacco smoke. This is also true from the quantitative point of view. Thus, due to enzymatic transformation during senescence and air-curing, e.g., the nicotine content may be reduced in favour of an increased amount of nornicotine. This may happen even to an extreme extent. Due to individual genetic conversion so-called “converters” are able to metabolize leaf nicotine to its nor congener up to 95% (Siminszky et al. 2005 and references therein). This happens more frequently in burley cultivars than in flue-cured tobaccos. Moreover, aging and flue-curing turned out to lead to a reduction on the concentrations of minor nicotinoid components.
The accumulation of large amounts of nicotine and/or its congeners is confined to four solanaceous genera belonging to two clades of the subfamily Nicotianoideae (Nicotianeae clade: Nicotiana; Cyphanthera clade: Crenidium, Cyphanthera, Duboisia).
Eckart Eich: "Solanaceae and Convolvulaceae: Secondary Metabolites: Biosynthesis, Chemotaxonomy, Biological and Economic Significance", Springer: New York, 2008, Ch 3.3 Nicotinoids (Tobacco Alkaloids) p83

Perhaps the eggplant/aubergine is one species to really worry about?

Particularly high levels of calystegines have been determined in Solunum melongena, eggplant/aubergine, and Capsicum annuum var. annuum, bell pepper/paprika. (Eich, p165.)
N-trans-Feruloyltyramine (E-feruloyltyramine) and its octopamine [2-hydroxytyramine = 1-(p-hydroxyphe- nyl)-2-aminoethanol] congener as well as N-trans-p-coumaroyloctopamine were discovered in the roots of S. melongena L., eggplant/aubergine. Furthermore, the already known N-trans-p-coumaroyltyramine was detected in this sample (Yoshihara et al. 1978).(Eich, p 299.)

These changes in the nicotin content are in the order of

The nicotine content in the tobacco leaves varies between 0.05% (Virginia tobacco) through 3 - 4% ("Burley") to 7.5% ("Machorka", Russia)

To compare that value for tobacco of the mild Virginia kind again with the eggplant from the letter in the first paragraph with the absurdly high values given there, assuming both kinds of plant material were ingested:

    source                       nicotine (ng/g) 

    nicotine from eggplant       ~100
    nicotine from tobacco     ~500000   

Keep in mind that eggplant values seem to be a sensational result of the unreplicated kind.
First hand smoking means not everything of that material is inhaled, some is burnt, some is lost to the environment. This concentration is much higher in commercial blends of tobacco found in cigarettes. The effect of second hand smoke is further diluted.

Nicotine is a very potent poison for most animals from protozoa to humans. The acutely fatal peroral dose for an adult is probably 60mg (Taylor 1995) which is equivalent to the nicotine content of five cigarettes or one cigar. However, smoking results in a considerable decomposition of this alkaloid due to pyrolysis; furthermore, much of the remaining volatile nicotine is not absorbed due to exhalation. (Eich, p98.)

The strict Swedish and Danish Health Council members conclude that

The average dietary exposure to nicotine from the food plants mentioned above was calculated to be 1.1 μg/day (88% from potatoes) in Sweden and 1.3 μg/day (70% from potatoes) in Denmark.
Nicotine is very toxic at high doses. The lethal dose in man is 50-100 mg, which approximately corresponds to the nicotine content of tobacco in 5 cigarettes. At lower doses it has many pharmacological effects.
In comparison, the total dietary exposure to nicotine is very low, and seems to be insignificant in relation to exposures giving rise to toxic and/or pharmacological effects.
The dietary exposure to nicotine is about two orders of magnitude lower than the exposure in passive smoking and around three orders of magnitude lower than the direct exposure during cigarette smoking (around 900 - 1 700 μg nicotine is assumed to be absorbed from a single cigarette). In addition to the difference in exposure level, absorption is much lower when exposure occurs in the diet than when by the inhalation route. Absorption from the stomach is poor and 60 to 70 percent of the nicotine is metabolised during the first pass through the liver, whereas absorption in the lungs is good and distributes nicotine systemically. Thus, it seems very unlikely that the low nicotine levels from dietary exposure would cause any toxicological harm in human.
_{Christer Andersson & Paula Wennström & Jørn Gry: "Nicotine alkaloids in Solanaceous food plants", TemaNord 2003:531}

Summary

Yes, nicotine can be detected in vegetables. Although this is quoted above, it worth repetition: "it would take an approximately 500-fold increase in the amount of vegetables estimated by Domino et al. to produce exposure equivalent to half a cigarette a day –– e.g more than 100 kg of tomatoes would have to be consumed in one day." Unless one employs very sophisticated concentration and purification methods (or plays the long game in breeding those plants for nicotine content) the concentrations of nicotine in commonly consumed vegetables are much too low as to be of any concern (or value, depending on perspective).