It is a well-known cautionary tale: the green parts of the tomato crop are toxic and should be discarded. But is that really the case? An unripe tomato that is still completely green does contain the toxic alkaloid solanine. This heat-resistant natural poison is found in all solanaceous crops, like potatoes. Just 25 milligrams of solanine is enough to make one feel uncomfortable: you get a headache and stomach ache and discomfort in your gut. You might suffer from visual disturbances after consumption. Over 400 milligrams would indeed be lethal. But green tomatoes are not that dangerous: a solanine content of up to 32 milligrams per 100 grams was measured. To be lethally affected, one would have to eat many kilos of green tomatoes.
Since we normally make salads with red tomatoes, we do not have to worry about solanine. Because when the tomato ripens, it turns red and the toxic green almost completely disappears. Some green spots are sometimes to be found that actually still contain solanine. You can cut these away if it makes you feel better, but they won’t do you much harm.