Will eating 200 apple seeds cause a fatal reaction? Not necessarily: Apple seeds contain a chemical compound that decomposes into cyanide but the compound must be released by finely crushing or chewing the seeds. The number of apple seeds needed to cause a fatal reaction is arbitrary, and it would take several apples to gather the number of seeds necessary to lead to any poisonous effect on the body.
The claim appeared in an Instagram post on November 13, 2021, that has a graphic with text that reads:
Apple seeds contain cyanide if you chew and eat 200 seeds you will die in a minute.
This is how the post looked on Instagram on December 9, 2021:
(Source: Instagram screenshot taken on Thu Dec 9 20:15 2021 UTC)
Apple seeds contain amygdalin, a chemical compound that releases a trace amount of hydrogen cyanide when it decomposes. Hydrogen cyanide may be highly poisonous in humans depending on the dosage. Amygdalin is also found in the pits of other fruits and in nuts.
According to a study published in 2015 in the peer-reviewed journal Food Chemistry, the amount of amygdalin in seeds from 15 varieties of apples was around 1 to 4 milligrams. The amount of cyanide from the amygdalin varies with the amount of amygdalin in the apple seeds, meaning that it would be difficult to pinpoint just how many apple seeds would be needed to poison -- let alone kill -- an eater. For example, Britannica estimates that the number could be anywhere from 150 to several thousand apple seeds.
The claim may have stemmed from a resource titled "Are Apple Seeds Poisonous?" published on Healthline. The "200 seeds" number was calculated based on human data figures from the Centers for Disease Control and Prevention (CDC). The data states that 1 to 2 mg/kilogram is a fatal oral dose of cyanide for a man who weighs 70 kg, or approximately 154 pounds. However, the CDC's entire note on those figures states:
Absorption of the alkali cyanides in amounts as low as 50 to 100 mg from a single, instantaneous dose may be followed by immediate collapse and cessation of respiration [Clayton and Clayton 1982]. It has been stated that although the fatal oral dose will vary considerably, depending on whether or not food is present in the stomach, it is probably in the order of 1 to 2 mg/kg [Clayton and Clayton]. [Note: An oral dose of 50 to 100 mg or 1 to 2 mg/kg is equivalent to a 70-kg worker being exposed to about 50 mg/m3 (as CN) for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]
As explained in the human data note, the figures are based on taking "a single, instantaneous dose" of cyanide and the results of such a dose "will vary considerably." In the case of the apple seeds, this most likely means that the seeds would have to be eaten in one sitting and their effect would be dependent on who is eating the seeds and what that person has already consumed.
Lead Stories reached out to food science experts for more information on this claim and will update this story with any relevant responses.