In Disney’s Snow White, a poisoned apple was given to the princess in efforts to send her into an everlasting slumber. The only way to wake her was from true loves first kiss. I guess this story is not far from the truth, with one small itsy bitsy caveat. For Snow White to go into her eternal slumber, she would have to consume 40 whole apples!

Well…What’s wrong with apples you may ask? Ahh, read on, you may just save your own life!

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Before you stop eating apples entirely please allow me to elaborate. It is not the apple flesh which concerns your body but the seeds themselves. You see, apple seeds, although rich in antioxidants and polyphenols contain poisonous compounds called cyanogenic glycosides.

Cyanogenic glycosides are naturally occurring plant toxins that are prevalent throughout the plant kingdom in more than 2500 species. They are stored inside plant cells and are completely harmless on its own. It is only when the compound is disrupted through chewing or crushing that the cyanogenic glycoside comes into contact with β‐glucosidase. β‐glucosidase is an enzyme that facilitates the release of hydrogen cyanide.

Yes… you read that right cyanide!

In plants and seeds, cyanogenic glycosides serve as an important defence against herbivores. In humans, cyanogenic plants can cause sub-acute cyanide poisoning with symptoms including anxiety, dizziness, confusion and headache. Acute poisoning, on the other hand can result in decreased consciousness, hypotension, paralysis, coma and in some cases death.

Cyanogenic plant foods

Cyanogenic glycosides are found in many plant foods, with the most common being amygdalin. Apple seeds contain a moderate amount of amygdalin, ranging from 1 to 4 milligram (mg) per gram (g) of apple seeds. Apple juice on the other hand contains between 0.001 and 0.08 mg per millilitre (ml) of amygdalin.

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According to the Centers for Disease Control and Prevention (CDC), 1–2 mg per kilogram (kg) is the lethal dose of cyanide for a 70 kg man. Therefore, if an apple core contained roughly 5 apple seeds, you would need to consume 40 apple cores or 200 apple seeds in order to receive a fatal dose. Let's be honest; it is improbable that you or I, would consume 40 whole apples in one sitting, and if you do then you certainly won't be keeping the doctor away!

Interestingly, there are some plants with even higher amounts of cyanogenic glycosides. Knowledge of preparing to remove any poisonous compounds from these foods have been passed down through generations and have been modified using modern-day technology.

Cassava is one of the most important tropical root crops. It’s carbohydrate-dense roots provide a significant source of dietary energy for more than 500 million people around the world. The United Nation Food and Agricultural (FAO) rank cassava as the fourth food crop in developing countries after maize, wheat potato. Yet, this crop is abundant cyanogenic glycoside compounds, mainly, linamarin, lotaustralin and amygdalin. Amygdalin content of cassava has been reported to be around 8.84–48.33 mg/g depending on the variety of cassava. To eliminate any potential poisoning, the cassava root is usually treated before consumption. The root can be boiled before eating, processed under heat and turned into flour or extruded into snacks.

Two of the most widely consumed species of cocoyams are Taro and Tannia. These species are commonly grown in tropical regions around the world and are valued for their corms and cormels (storage organs for the plant) which can be converted into flour, congee or extruded snacks. Besides industrial processing, they can also be consumed by baking or simply boiling. Due to their high carbohydrate content, edible cocoyams are a rich source of calories for many individuals around tropical regions. Cocoyams also contain other sources of nutrients such a protein, vitamins and minerals. Yet, similar to cassava these tuber crops contain around about 10.84 mg/g of amygdalin in its raw form.

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The Final Verdict

Now, although Disney did not get it completely right when they sent Snow White into an eternal slumber, at least we now know that it would take far more than one magical apple to completely knock us out. Although some health gurus recommend people to consume some fruits and vegetables entirely raw, we must realise that nature has created these delightful treats to survive and persevere in harsh conditions. We are only finding out now how these poisonous compounds are affecting our bodies through science. However, our ancestors have always known the correct methods and procedures on how to handle these foods.

In saying that, I encourage everyone to always do their own research, be curious about food. Yet, not so curious that you end up hurting yourself. Skip the seeds so an apple a day can still keep the doctor away!

Part-time food scientist and full-time foodie — Piecing together the disconnect of food, health and well-being.

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