Toxicity in Natural Foods: Everything You Need to Know

Have you ever wondered whether fruits and veggies have the potential to cause harm to your body similar to certain fast foods? The answer is yes, and this may come as a surprise to many people. Just like some animals, plants produce their own chemical substances to protect themselves from being eaten up by predators. Similar to their physical defense systems like hard shell coverings, spikes and thorns, certain fruits and vegetables contain naturally occurring toxins. When consumed improperly or excessively, these toxic compounds can have adverse effects on health. This article aims to provide an overview of how some common plant-based natural foods we consume every day can turn toxic when consumed without the necessary awareness.

Side effects of consuming natural toxins can range from mild symptoms like itching, nausea, vomiting, and stomach upset to more dire consequences including paralysis, liver damage, coma, or even death. These enter the body not only through consumption, but through other ways like inhalation and touching. Not all the toxic compounds are located in the same region of the fruit/vegetable; for some, the toxins may be located within the seed, whereas, for others it may be located on the outer peel. These chemicals have been studied and classified into various categories for fruits, vegetables, nuts and spices. For example, cyanogenic compounds (cyanides) can exist in the seeds of a fruit, and mycotoxins (fungal toxin) can occur in spices like chilli, turmeric, and pepper.

Vegetables & Fruits

·       Cruciferous vegetables: Veggies like broccoli, cauliflower, and cabbage naturally contain a chemical compound called thiocyanates. When these vegetables are consumed in enormous quantities, thiocyanates can reduce the body’s ability to absorb iodine, and this in turn may cause thyroid disorders. Generally, people with underactive thyroid gland are advised to limit their intake of these vegetables as it can aggravate their existing condition. Moreover, it is advised to cook them before consuming as it helps reduce this harmful compound.

·       Potatoes: Unlike cruciferous vegetables, the toxin found in potatoes does not get reduced or eliminated upon cooking. Solanine and chaconine are responsible for symptoms like digestive disturbances, diarrhea, headaches, weakness, cramps, and confusion, and in severe cases even coma and death. Prolonged exposure of potatoes to light makes it appear green in color, indicating the presence of toxins developed in them. It is usually concentrated in the peel and sprouts of potatoes.

·       Parsnips: Similar to potatoes, these vegetables have the highest amount of toxin (furocoumarins) in the outer peel and also in the damaged parts. When the outer peel and damaged areas are not eliminated before eating or cooking, it can cause stomach pain and skin reactions.

·       Sweet potatoes: Sweet potatoes, otherwise known as kumaras, can produce toxic chemicals as a result of damage, stress, injury or insect attack. The chemicals are found in highest concentration in the damaged areas, and this gives rise to a bitter taste. Removal of damaged parts before cooking is highly recommended.

·       Tomatoes: Green unripe tomatoes and the plant leaves contain tomatine which can cause nervous excitement and stomach upset when consumed. It is best to wait until they are ripe before consuming.

·       Cassava: Cassava has cyanogenic compounds in the outer peels which can cause dangerous neurological and digestive problems when consumed without peeling or cooking them well. For sweet cassavas, peeling and cooking is generally sufficient to remove toxins, whereas bitter cassavas need to be peeled, cut, and soaked for a long time to eliminate toxins before cooking. Poisoning from cassava can cause blood pressure to reduce significantly with other symptoms like faster breathing, increased pulse rate, headache, dizziness, confusion and stomach issues.

·       Apples & Stone Fruits: Apples and stone fruits like apricots, peaches, cherries, and plums contain cyanide in their pit kernels. Swallowing the seeds or pits of one fruit accidentally may not have a toxic effect, but consuming in excess quantities can cause serious issues. When the seeds are chewed and swallowed it releases the cyanide present within the kernel and this is what makes it poisonous.

Nuts

·       Raw Cashews: Cashews, in their raw form contain a resin called urushiol, the toxic compound which is responsible for itching and skin reactions similar to poison ivy. Before hitting the market shelves, the cashews are usually cooked to remove these raw compounds as eating higher quantities of unprocessed cashews fresh from the trees can turn fatal. One must always ensure that the cashews are sourced from credible outlets and refrain from eating freshly harvested ones.

·       Brazil Nuts: In contrast to all fruits, nuts, and vegetables mentioned previously, the potential toxicity in Brazil nuts comes from an essential mineral present in them -which is selenium. Selenium toxicity can lead to hair loss, digestion issues, and memory problems and one should limit their intake to 3 to 4 nuts per day (for adults) and must not consume in excess.

Spices

·       Cinnamon: While Cinnamon contains excessive amounts of antioxidants, it can also be dangerous when consumed in excessive amounts. It contains a chemical compound called coumarin which can cause liver toxicity and increase the risk of cancer.

·       Nutmeg: It contains a compound called myristicin which can cause poisoning when consumed in higher doses; symptoms include nausea, dizziness, hallucinations, and sometimes even seizures in severe cases.

Beans & Pulses

·       Mung beans contain anti-thiamin compounds, which act like an antivitamin, inactivating vitamin B1 (thiamine). When consumed without proper washing, soaking and boiling, especially in high quantities, mung beans can present symptoms similar to vitamin B1 deficiency which includes muscle pain, weakness, nervous tingling, and irritability.

·       Kidney beans also contain a toxin called phytohemagglutinin which causes stomach pain, diarrhea, and vomiting when consumed raw or half cooked.

Foods sourced from nature are abundant sources of nutrients and essential elements vital for our body when compared to highly processed foods. But for a few types of natural foods, extra caution is needed while storing, eating, soaking and cooking them to reduce damage caused by their toxins. Sometimes, these compounds cannot be completely eliminated even after cooking; so, it is advisable to cut down the portion size for safety. Generally, common foods like beans must be soaked, washed and cooked thoroughly in fresh water to gain maximum nutrition and avoid any harmful effects on the body. For potatoes, the way we store them can directly impact its fit for consumption; storing them in a cool, dry, and dark place is essential to reduce the chances of toxin formation. Overall, the information provided here is just a quick guide to understand the way of storing, processing and consuming natural foods in order to render them beneficial rather than causing harm.

References

1.       Sultan, A., Afroza, B., Mufti, S., Malik, A. A., Sakib, N., Akhter, A., Indrabi, S. A., & Javeed, I. (2020). Vegetable Food Toxicants and their Harmful Effects on Health. International Journal of Current Microbiology and Applied Sciences, 1923–1936. https://www.ijcmas.com/special/11/Amreena%20Sultan,%20et%20al.pdf

2.       UHBlog. (2024, June 25). 8 Healthy Foods That Can Be Risky in Excess. 8 Healthy Foods That Can Be Risky in Excess. https://www.uhhospitals.org/blog/articles/2024/06/8-healthy-foods-that-are-risky-in-excess

3.       Canadian Food Inspection Agency. (2019, December 9). Natural toxins in fresh fruit and vegetables. inspection.canada.ca. https://inspection.canada.ca/en/food-safety-consumers/fact-sheets/specific-products-and-risks/fruits-and-vegetables/natural-toxins

4.       Pantry, fridge, countertop: Where to store your food. (n.d.). WebMD. http://webmd.com/food-recipes/ss/slideshow-where-to-store-food

5.       Program, H. F. (2024, September 26). Natural toxins in food. U.S. Food And Drug Administration. https://www.fda.gov/food/chemical-contaminants-pesticides/natural-toxins-food

6.       Breyer, M. (2021). 8 Fruits and Vegetables With a Poisonous Side. Treehugger. https://www.treehugger.com/poisonous-fruits-and-vegetables-avoid-4858734

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