THE APPLE SEED CYANIDE MYTH
By Mike Owen
One of the enduring myths of bird keeping, especially among companion parrot owners, is that apple seed contains enough cyanide to kill a bird and all the apple seeds need to be removed before feeding. In recent times an additional myth about apple seed has emerged, with arsenic being the killer constituent.
This is in spite of the large numbers of aviculturists and pet owners who have included the core and seed of apple when feeing their birds the fruit over many years without any effect on their birds. Like those fellow aviculturists, I also have never worried about apple seeds when giving apple to my parrots and some of my birds are still going strong after 25 years of having apple seed included in their daily food mix.
The myth appears to have started with a grain of truth in that there is a compound in apple seed - amygdalin - which can break down in the stomach to release cyanide. Amygdalin is present in very small amounts and the amount of cyanide it could possibly produce is present in even smaller amounts. Further, the liver and kidneys are very efficient at removing cyanide and it is not an accumulative poison, so a lethal dose is needed all at once or else the liver easily handles and removes small amounts without any lasting effects.
Interestingly almonds also contain amygdalin and a couple of almonds would give the same amount of amygdalin as eating all the seeds in an apple core. Even sunflower and sorghum contain a small amount of amygdalin.
For those wanting to know the scientific basis for saying apple seed is harmless a very recent paper has appeared in the scientific journal "Food Chemistry" looking at the amygdalin levels in the Rosaceae group of plants - which includes apples, apricots and almonds. For those interested the article is Amygdalin content of seeds, kernels and food products commercially-available in the UK -- Food Chemistry 152 (2014) 133–139
That article shows levels in the Rosaceae group range from 0.1–17.5 mg per gram, with apple seeds being at the low end around 3.0 mg per gram of seed. Since it takes about 20 apple seeds to make 1 gram, each seed will contain 0.15 mg of amydalin. And further, one gram of amygdalin would release 68 mg of hydrogen cyanide if fully broken down in the digestive system. For that to happen a bird would have to thoroughly masticate (chew) the seed before swallowing it—a whole seed that was swallowed would release very little of it’s potential cyanide. So a quick calculation shows that each seed is capable of releasing 0.01 mg of cyanide in a worst case scenario. The lethal dose for parrots has not been determined but for quail, starlings and chickens it ranged from 10 to 20 mg/kg (Journal of Wildlife Diseases 22(4):538-546. 1986). So taking a conservative estimate of 5mg/kg for parrots, a 100 gram parrot would need a dose of 0.5 mg of cyanide, and have to eat at least about 50 apple seeds in one sitting. Since the average apple contains 4 to 6 seeds, that 100 gram cockatiel is going to have to get through the seeds from 10 apples in one meal to cause any problems. A 500 gram bird such as a large African Grey would have to face 50 apples and 250 apple seeds at a sutting! So both the science and practical experience show that apple seeds are of no danger to a bird.
As for arsenic, there is none to speak of—apple trees are relatively inefficient at pulling arsenic out of the ground, and what they do extract from the soil goes mostly into the leaves, with a very small amount ending up in the flesh of the fruit— in fact a very very small amount!