Rumor:

The raw tomatoes contain the highly toxic substance lobelia alkaloids, raw food will cause death.

Rumor:

Tomato, belonging to the family of plants (genus solanum), we usually see potatoes and eggplants belong to the family of plants. Solanaceae plants commonly produce lycorine, or solanine (solanine, chemical formula C45H73NO15, named because it was first found in lobelia). Lobelia, which is toxic to insects and animals, is a sugar alkaloid substance (glycoalkaloids) produced by the plant for its own defense.

The mechanism of toxicity of lobelia alkaloids is mainly through the inhibition of cholinesterase activity and cause toxic reactions in humans, poisoning is mainly manifested in the gastrointestinal tract and nervous system disorders. A study has shown that an intake of 2-5mg/kg of lobelia in the human body can cause symptoms of poisoning, while an intake of 3-6mg/kg may be fatal. Symptoms usually appear 8 to 12 hours after ingestion and may occur as soon as 10 minutes after eating foods high in lobelia.

Tomatoes also contain some amount of glycoside alkaloids, but the alkaloids are not lobelia alkaloids, but tomatine (chemical formula C50H83NO21). It can be seen that this rumor first made the mistake of Zhang Guanzhi. Tomatine is more abundant in green tomatoes than in ripe tomatoes, and tomato leaves are the part of the tomato plant with the highest tomatine content. But we don't normally eat green tomatoes, much less tomato leaves, and there's no such thing as food poisoning that comes with them.

Secondly, lycorine is less toxic than lobelia. Experiments have shown that the safe dose of lycorine for consumption is about 2 milligrams per kilogram of body weight. In other words, an adult weighing 50 kilograms would have to eat more than 100 milligrams (0.1 grams) of lycorine to have a chance of being poisoned.

0.1 grams may seem like a lot, but if we consider the amount of lycorine in tomatoes, we can see that it is very unlikely that toxicity would occur after eating raw tomatoes. In order to study the activity of tomato alkali, our researchers weigh 30kg green tomato pulp, with anhydrous ethanol as the material liquid, through ultrasonic extraction, chloroform extraction, resin adsorption, distilled water elution, 95% ethanol elution and other methods, and finally accurate weighing to get the tomato alkali crude about 1.093g. This means that once you have to eat at least 3kg of raw tomatoes to have the possibility of poisoning. In addition, it has been claimed in the literature that it takes about one pound of tomato leaves (about 0.45 kg) to produce lycorine, which induces toxicity in adults. So under normal circumstances, eating one or two unripe green tomatoes is not toxic.

However, when the human body eats raw green tomatoes in large doses and ingests fairly high doses of lycorine, it does have the potential to produce gastrointestinal problems and even damage to the liver and heart. As tomatoes ripen, the amount of lycopene in them becomes lower and lower, so there is basically no possibility of lycopene poisoning from eating ripe red tomatoes raw.

In a nutshell, the content of the alkaloids in tomatoes is negligible, and the relatively high content is the same as that of the glycosidic alkaloids of the lycopene alkaloids. However, both the relatively abundant lycorine content of green tomatoes, or very low content of ripe red tomatoes, normal consumption is not enough to produce damage to the human body. Consumption of large quantities of unripe green tomatoes may cause gastrointestinal problems such as diarrhea and should be avoided.

References:

[1]Solanine.(2011, Feb). In Wikipedia, the encyclopedia. Retrieved December 12, 2019

[2]Hariet Hall.(2012, Feb). Killer Tomatoes and Poisonous Potatoes? Retrieved December 12, 2019

[3]Donald.G.B, (2009). Potatoes, tomatoes, and solanine toxicity (Solanum tuberosum L., Solanum lycopersicum L.). Disease-a-month, 55(6):391-402.

[4]Amy Grant.(2019, Jul). Tomato plant toxicity-can tomatoes poison you. retrieved December 12, 2019

[5]Harold Mcgee.(2009, Jul). Accused, Yes, but Probably Not a Killer. Retrieved December 12, 2019

[6]Xu Qiaoxia, Du Ping, Su Yeping, Huang Feng, Jin Jianxiu, Liu Honghai. Study on the isolation and purification of lycorine from green tomatoes[J]. Processing of Agricultural Products, 2010(03):71-72+75.

[7]A new study in Spain found that tomatoes are healthier when eaten cooked[J]. Chinese Journal of Food, 2018, 18(06):52.

[8]Executive Summary of Chaconine & Solanine.

Discrediting expert: Lu Jiangkun Zhong, PhD student, Osaka University School of Medicine, Japan

Reviewing expert: Lu Shuoyuan Zhong, Researcher, Osaka University Immunity Frontier Research Fellow, Osaka University Immunization Frontier Research Institute, Japan