Amygdalin is a compound in the seeds of many fruits, like peaches and bitter almonds. During metabolism, it produces hydrogen cyanide (HCN). Amygdalin is a subject of ongoing debate in science and health.
About Amygdalin
Amygdalin is a cyanogenic glycoside, or compound containing sugar which releases cyanide when broken down. It's famously found in the seeds of apricots, almonds, cherry laurel, apples, peaches, plums and bitter almonds.
Almonds are often called nuts but they are in fact fruit, or more specifically drupes, as are peaches. Like the pistachio and cashew (drupes without amygdalin), an almond is a large seed in the fruit's hard outer casing.
Amygdalin is a combination of a sugar molecule and a cyanide group. The structure of amygdalin comprises one unit of benzaldehyde, one unit of hydrocyanic acid, and two units of glucose.
Bitter almonds contain about 5% amygdalin, a risk in large amounts. Sweet almonds, common snacks, have negligible levels of amygdalin. For baking, amygdalin is usually removed from almonds before they hit the shelves.
How Amygdalin is Created
Amygdalin is synthesized naturally within the cells of over 2000 plant species. It's formed through a complex series of biochemical reactions by a multitude of enzymes.
The precise biosynthesis pathway varies slightly depending on plant species. Aromatic amino acids are enzymatically modified, ultimately leading to the formation of the amygdalin molecule.
Plants create amygdalin as protection. When a plant is chewed by herbivores, the enzymes are activated to start the conversion of amygdalin into hydrogen cyanide. The compound has a bitter burning taste.
Apple seeds for instance contain amygdalin to discourage animals from chewing them when dining on the sweet fruit. This ensures seeds pass through the animal's digestive tract safely, to germinate on the other side.
Cyanogenic Compounds
The toxicity of cyanogenic compounds depends on several factors. These include the specific compound, the amount ingested, the presence of enzymes to break it down, and the individual's ability to detoxify cyanide.
Common examples of plants containing cyanogenic compounds include cassava, sorghum, flaxseed and fruits with amygdalin-containing seeds. Flaxseeds release hydrogen cyanide when they're crushed and come in contact with fluids.
Cassava, a prevalent starch source of the tropics, is commonly soaked or boiled before consumption to defuse the toxins. Livestock like cows have a higher risk of cyanide toxicity when grazing on plants like sorghum.
Amygdalin itself isn't directly toxic. The enzyme β-glucosidase, found in the digestive microbiota as well as the seeds, breaks it down to release cyanide.
The human body has some capacity to detoxify small amounts of cyanide with the enzyme rhodanese. This converts cyanide to a less toxic form, thiocyanate, excreted in the urine.
Too much cyanide overwhelms the detox pathway. Symptoms of toxicity can manifest as headaches, confusion, nausea, dizziness, and in severe cases, can escalate to convulsions, coma and death.
Between 0.5 to 3.0 mg of cyanide per kg of body weight can be toxic in varying degrees. One would need to eat about 10 to 20 apple seeds for severe toxicity.
Animals present similar symptoms, which may not be recognized right away, depending on the animal's size and behavior. The key indicator is sudden illness or death after ingesting fruit seeds or kernels.
Facts About Amygdalin
"Laetrile" Controversy: Amygdalin gains notoriety as "Laetrile," a purported cancer treatment promoted in the 1970s. However, numerous scientific studies have shown that Laetrile is ineffective in treating cancer and can be dangerous due to cyanide poisoning.
Bitter Almonds: Bitter almonds contain significantly higher levels of amygdalin than sweet almonds. For this reason, bitter almonds are often processed to remove the amygdalin before being used in food products.
Genetic Diversity: The amygdalin content in different varieties of fruits can vary significantly due to genetic differences. Breeding programs can select for varieties with lower amygdalin levels.
Ongoing Research: While its use as cancer treatment is debunked, research continues on amygdalin, focusing on its potential anti-inflammatory and antioxidant effects. These studies are still in early stages.
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