Key Message: Man-made chemicals such as pesticides, veterinary drugs or environmental pollutants are things that come from outside the food supply, but natural toxins are different and are already in the food. Natural toxins are already present in some edible plants and animals, and people can have adverse effects if they consume sufficient amounts.

Where do Natural Toxins come from?

Toxic compounds come from a variety of plants and animals. Natural toxins may be present in food and animals for specific functions, or they may be chemical defenses against predators, insects or microorganisms. These chemicals have various chemical structures, and their properties and toxicity are also various.

Natural Toxins in Edible Plants

Of the more than 300,000 known plant species worldwide, at least 2,000 are poisonous. It is not uncommon for people to be poisoned by eating wild mushrooms, jam fruits or other plants. There are only a few hundred species of plants in the world that people eat regularly, but many of them can be harmful if eaten in excess or without proper treatment. Depending on the species of plant, the edible parts will vary and can be leaves, leaf buds, stems, roots, fruits or tubers, as can the poisonous parts.

Food Measures for reducing the risk
Green bean, lentils, concanavali, red kidney bean, white kidney bean, soybean

Cook thoroughly at boiling temperature after thorough soaking in water.

Canned beans have undergone high heat treatment and therefore the toxins are destroyed.

Bamboo shoot, cassava Remove the peel, soak in water, cut into small pieces and cook thoroughly in boiling water.
Bitter apricot seed, flaxseed Cook thoroughly in boiling water; limit the intake if cooked by other methods.
Potato Store in a cool place (no need to put in the refrigerator); do not consume sprouted, greened or damaged potatoes.
Ginkgo Do not consume raw; limit the intake to a few seeds per day, especially for children.
Fresh lily flower (fresh Jin Zhen) Cook thoroughly; dried lily flower (dried Jin Zhen) can be safely consumed.
Black fungus Dried black fungus contains no toxins, but should be kept in the refrigerator if soaking for a long period of time is needed to prevent contamination by bacteria.

Natural Toxins in Food Animals

Natural toxins of animal origin may be the metabolites or chemicals in the food chain. Although food poisoning cases caused by consuming terrestrial animals is rare, poisoning caused by marine toxins is common worldwide. Shellfish, crustaceans and fish build up toxins in their bodies after eating marine toxins produced by toxic microalgae. Tetrodotoxin is a highly toxic neurotoxin believed to be produced by certain bacteria. More than 90 species of puffer fish contain tetrodotoxin, which can be fatal even if consumed in small amounts. Since ciguatoxin can be found in more than 300 species of reef fish, marine food poisoning reports frequently involve these fish. Another type of seafood poisoning can be caused by histamine from bacterial spoilage in mackerel.

There are about 1,200 species of venomous and venom glands containing animals in the world. Although most are not edible, it should be cautious to avoid venom glands or toxin-containing tissues when used as food. Food poisoning can also be caused by ingesting certain glandular tissues of animals that are not generally considered poisonous, such as carp gallbladder containing cyprinol.

Food Risk Reducing Measures
Shellfish May contain shellfish toxins. Remove the internal organs and genitals before cooking. Consume a small amount of shellfish only at a time, and avoid drinking cooking juices because some shellfish toxins are soluble in water.
Coral reef fish Consume only a small amount at a time, and avoid eating eggs, liver, intestines, head and skin. Avoid alcoholic beverages or nut products when eating this type of fish as they are known to exacerbate poisoning symptoms.
Mackerel Refrigerate fish that may contain histamine (such as tuna, mackerel, sardine and anchovy) properly at 4°C or below.

In addition, pufferfish can contain tetrodotoxin, which is a highly toxic neurotoxin. Members of the public should not fish, wash and cook puffer fish.