Ground Flaxseed – How Safe is it for Companion Animals and for Us?

Abstract

EFSA released the 89-page Scientific Opinion “Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels”. This opinion, and the ensuring media coverage, has left uncertainty in the minds of consumers, feed and supplement manufacturers and flaxseed producers of how much ground flaxseed can safely be consumed without crossing the threshold of cyanide toxicity. This editorial updates the science and tries to bring clarity to the question “how much flaxseed can I safely feed my dog, cat, horse on a daily basis?” and “how much can I safely eat?” The great majority of ground flaxseed products have a cyanogenic glycoside content of less than 200 mg / kg seed. For people, consuming 30 grams of such flaxseed the average peak blood cyanide concentration will be about 5 µmole / L, much less than the toxic threshold value of 20 to 40 µmole / L favoured by EFSA.  Thus, as much as 120 grams of crushed / ground flaxseed can be consumed by a 70 kg adult person before a toxic threshold of 40 µmole / L is reached (up to 1.7 grams ground flaxseed / kg body weight). The toxic threshold of cyanide for dogs is 2 to 4-fold greater than for humans, and unknown for cats and horses. The daily serving amounts for dogs and cats are about 0.23 grams / kg body mass per day, which will result in blood cyanide well below the toxic threshold. The highest recommended daily serving amount for horses is 454 grams per day, or 0.8 to 2 grams per kg / body mass depending on mass of the horse. This amount for horses should not be exceeded.