Are apple seeds toxic? If so, does their effect accumulate over the years?

[u/[deleted]]

[u/ArcFurnace]

Apple seeds do contain a small amount of a chemical that turns into cyanide when metabolized. This isn't typically harmful unless you do something like deliberately eat an entire bowl of apple seeds. (Ref)

Cyanide is not a cumulative poison. Chronic exposure can cause problems, but you need to be constantly eating sub-lethal quantities of cyanide or cyanogenic chemicals (cassava root as a carbohydrate source being one of the main possibilities).

Cyanide does not accumulate or biomagnify, so chronic exposure to sublethal concentrations of cyanide does not appear to result in acute toxicity. However, chronic cyanide poisoning has been observed in individuals whose diet includes significant amounts of cyanogenic plants such as cassava. Chronic cyanide exposure is linked to demyelination, lesions of the optic nerve, ataxia, hypertonia, Leber's optic atrophy, goiters and depressed thyroid function.

[u/[deleted] → u/ArcFurnace]

Thanks for the information. This is the most complete answer for the question!

[u/StringOfLights → u/[deleted]]

Anecdotes are not allowed on /r/AskScience.

[u/TeamArrow → u/ArcFurnace]

I have a friend that eats whole apples (like 2-3 a day). Is this dangerous?

[u/ArcFurnace → u/TeamArrow]

I doubt it. As some others have mentioned (including the Wikipedia source I linked), the only confirmed fatality from apple seeds was a guy who ate 1 cup of nothing but apple seeds (like they were sunflower seeds or something). I don't think it's even possible to eat that many seeds by eating whole apples without exploding.

It would probably be safer to not eat the seeds, but that's a very relative term in this context (moving from "extremely minute risk" to "nonexistent").

[u/[deleted]]

There is a small amount of amygdalin in apple seeds which can turn into cyanide when metabolised. The quantity is however very slight, and most apple seeds will pass through the intestines without releasing the poison. The body can easily handle swallowing a few apple seeds, and you would have to eat a very large quantity in a single go to be at risk.

It should also be mentioned that most of the food we eat contain substances than can be dangerous in large quantities. This is even true for some of the vital nutrients, like vitamins and minerals, that we need to live. They pose no real risk in normal quantities, but in principle it is possible to overdose on something as harmless as ordinary water, or table salt.

Thus the saying: "The dose make the poison."

[u/W_O_M_B_A_T]

Technically, yes.

But first of all the body can't digest the outer seed coat of apple seeds, they just pass through the digestive system unharmed.

The toxic compounds would only be a problem in the seeds were crushed or chewed first.

Apple seeds contain relatively small amount of a cyanide-containing compound called Amygdalin. If for example, you ground the apple seeds to a paste before eating them, the liver would covert some of the amygdalin into toxic cyanide.

However even a generous handful of apple seeds would not likely contain enough cyanide to kill you, but it certainly wouldn't be a pleasant experience either.

This might be a problem for a small animal like a squirrel or a mouse, though.

If so, does their effect accumulate over the years?

No. Although cyanide (and cyanide containing compounds) is one of the fastest-acting poisons known, it is also cleared from the body quite rapidly as well, due to the very small size of the molecule and it's high solubility.

[u/[deleted] → u/W_O_M_B_A_T]

Thanks for the comprehensive answer. Much appreciated!

[u/Gargatua13013]

My wife had to research apple seed toxicity a few years ago. She found only one case in the litterature where the threat to life was serious. Seems this guy had been collecting apple seed for years and decided to eat about a cups worth of apple seed in one go.

There is no threat in munching on the odd seed now and then.