Did you know that there are natural toxins found in foods? They are naturally produced by the plant or animal as self-defense against predators, insects and microorganisms or are produced as response to extreme weather conditions. These toxins are not harmful to the plant or animal but can be toxic to vulnerable individuals who ingest them in high amounts or simply by contamination of common food. The following are examples of natural toxins in foods and how to avoid them:

1. Algal Toxins and Ciguatoxins in Fish or Shellfish may cause food poisoning, paralysis and even death.

There are two main types of toxins found in either fish or shellfish: algal toxins and ciguatoxins. Algal toxins are produced by algae which are small organisms that are usually consumed by shellfishes. They are harmless when they are eaten by shellfish such as oysters, scallops and mussels but these toxins may accumulate in their body and cause disease to humans when they eat shellfish with high amounts of this toxin. It can lead to paralytic shellfish poisoning (PSP), which can lead to death in two hours. Other symptoms of shellfish poisoning include diarrhea, vomiting, tingling sensation, confusion and paralysis.

Ciguatoxins on the other hand, are primarily produced by planktons which are eaten by big fishes such as barracuda, black grouper, eel, sea bass, dog snapper and king mackerel. These toxins may accumulate in their flesh and may cause disease to humans such as ciguatera fish poisoning when they eat a fish contaminated with ciguatoxins. Symptoms include nausea, vomiting, tingling, numbness, muscle pain and dizziness.

These toxins in fish and shellfish have no distinct taste, color or smell and are not eliminated by cooking or freezing. Thus, it is important to stay updated on public health warnings to not consume shellfish during red tide season or when there have been reported cases of fish or shellfish poisoning in the area.

2. Cyanogenic glycosides in cassava, root crops and some fruits may cause difficulty in breathing and convulsions.

Cyanogenic glycosides are toxic chemicals produced by plants such as Cassava, bamboo roots, bitter almonds, and some stone fruits like cherries, peaches, pears and plums. In fruits, most of the toxin is concentrated in the pit and it breaks down into hydrogen cyanide inside the body when eaten. However, the flesh of the fruit itself is safe but it is not recommended to eat the large seed or pit. Symptoms of acute cyanide intoxication include rapid breathing, dizziness, headache, abdominal pain, vomiting, diarrhea, confusion, cyanosis (bluish or gray skin, nails or lips) and convulsions followed by terminal coma.

To prevent intake of these toxins:
● Cassava - Use gloves when peeling, grate and soak the root crop in water and cook completely to reduce the levels of toxin. Remove blemished or discolored spots.
● Bamboo roots - Boiling is recommended.
● Stone fruits like cherries, peaches, pear and plum - Eat only the flesh of the fruit, do not eat the large seed or pit

3. Mycotoxins in cereals, dried fruits and nuts may contribute to cancer and immune deficiency.

Mycotoxins are naturally occurring toxic compounds produced by certain species of mold. Different types of mycotoxins include aflatoxins, ochratoxin and trichothecene. Molds can grow on certain foods such as cereals, dried fruits, nuts and spices and may still be present even after food processing. Mycotoxins such as aflatoxins have been found to be potent and are associated with the development of several types of cancer.

To avoid intake of these toxins:
● Buy cereals, dried fruits, nuts and spices from reputable sources only.
● Choose properly sealed products which are free from moisture which may promote the growth of molds.
● Store properly and take note of the expiration date
● Do not consume once beyond their expiration date or once visible molds or signs of spoilage are observed

4. Solanine and chaconine in potatoes may cause food poisoning.

Solanine and chaconine are natural toxins produced by Solanaceae plants such as tomatoes, potatoes and eggplants. They are more concentrated in potato sprouts, peels and its green parts. In high amounts, it may cause vomiting, abdominal pain, diarrhea, headache, flushing, confusion and fever. These toxins are not destroyed by cooking thus high levels may cause a bitter taste or a burning sensation in the mouth.

To reduce this toxin from potatoes:
● Store potatoes in a dark, cool and dry place
● Wash potatoes before cooking
● Peel or cut away green areas prior to cooking
● Discard potatoes with pronounced greening or damage

5. Poisonous mushrooms may cause hallucinations and even death.

Wild mushrooms may contain toxins such as muscimol and muscarine, which can cause vomiting, diarrhea, confusion, visual disturbances, salivation and hallucinations. Symptoms of mushroom poisoning include severe abdominal pain, vomiting, diarrhea and intense thirst. If toxins damage the kidneys, liver or central nervous system, poisoning can lead to death. Cooking or peeling does not deactivate these toxins; thus it is important to be aware and avoid poisonous mushrooms.

To avoid intake of poisonous mushrooms:
● Do not pick mushrooms randomly for consumption especially if you are not familiar with edible mushrooms
● Buy only mushrooms from the supermarket or from reputable sources with proper food label
● Don’t pick mushrooms with white gills, a skirt or ring on the stalk or a sack-like base
● Avoid mushrooms that have red stalks or caps
● Never eat a mushroom you're not 100 percent certain that is safe to eat.

/AET

References:
Canadian Institute of Food Safety. (2019). Understanding Natural Toxins in Food. Canadian Institute of Food Safety. Retrieved from https://www.foodsafety.ca/blog/understanding-natural-toxins-food#:~:text=Mycotoxins,dried%20fruits%2C%20nuts%20and%20spices.

Dolan, L. C., Matulka, R. A., & Burdock, G. A. (2010). Naturally occurring food toxins. Toxins, 2(9), 2289-2332.

World Health Organization (2018). Natural toxins in food. World Health Organization. Retrieved from https://www.who.int/news-room/fact-sheets/detail/natural-toxins-in-food