Natural toxic substances in foodstuffs

Fruit and vegetables are an important part of a healthy diet. They contain chemical compounds, such as carbohydrates, sugars, proteins and vitamins, which are essential to human growth and health. However, plants inherently also contain various harmful or toxic substances the purpose of which is, for example, to fend off the adverse effects of insects or different diseases, or to protect the plant against perishing.

The natural toxins of plants may also have adverse effects on the health of people who eat the plants. The nature of the toxin, its content in the edible part of the plant and the individual sensitivity of people to different substances determine whether the toxin causes any clinical signs. The content of harmful substances can often be influenced through proper handling. For example, some toxins, such as gyromitrin contained in false morels, are water soluble or volatile and will therefore decompose when boiled. In other words, the natural toxic substances contained in foodstuffs can be avoided by choosing and handling the foodstuffs correctly.  

Food operators are responsible for the safety and conformity with requirements of the foods that they sell and market. Natural toxic substances in foodstuffs are not stipulated for in any specific regulations, but other food laws lay down limit values for the tolerable daily intake of some toxins, such as coumarin, nitrate, glycoalkaloids and cyanoglycosides, or maximum permitted amounts for certain food groups. Evira has provided specific handling instructions for some foods, such as beans and false morels, to reduce the content of harmful substances in them. Regulations require that a warning always be posted at the point of sale of fresh and dried false morels giving information about their toxicity as well as handling instructions. Authorities must control that warnings are posted at points of sale.


Natural toxic substances in foodstuffs include

  • glycoalkaloids, such as solanine in potatoes and tomatine in raw tomatoes 
  • nitrates in vegetables
  • gyromitrin in false morels
  • lectins in beans
  • coumarin in cinnamon
  • biogenic amines in fruits and vegetables
  • cyanoglycosides in fruit seeds and stones and in cassava.