"Should We Be Concerned About the Cyanide from Flaxseeds?"
Flaxseeds pack a nutritional punch.
And as a bonus the release of cyanide from flaxseed
is below a toxic lethal dose. Well, I should hope so.
Back-of-the-envelope type calculations have led
industry-funded scientists to assert that a person would have to consume
8 cups of ground flaxseed at a time to achieve acute cyanide toxicity.
I'd feel better though if it was actually put to the test.
Researchers tested flaxseeds under worst-case scenario conditions,
with respect to resulting in higher cyanide levels in the blood.
So (1) locate the flaxseed with the highest level
of cyanide-forming compounds you can find.
So they went to stores
and bought 15 different sources of flaxseed, and though the average level
was 140 milligrams per kilo, which is about typical,
they did find one with 220, so they used that one.
(2) maximal mechanical destruction to release the most cyanide.
So they used some crazy 20,000 RPM lab grinder.
(3) eat it all at once on an empty stomach,
and then keep the stomach empty.
And they gave it raw, since cooking can often wipe it all out.
If the recommended daily dose is like one or two tablespoons
of ground flaxseed a day—I recommend one in my Daily Dozen checklist—
they decided to go with four and a half tablespoons.
OK, so what happened?
The range of cyanide blood levels that one might estimate to possibly
be associated with the clinical symptoms of intoxication would be like 20 to 40.
So that would be like here or higher, where we want to stay below.
So four and a half tablespoons on an empty stomach
of the highest cyanide-containing ultra- ground raw flaxseeds they could find,
and the highest individual level rise was just under 14,
and the average was down around 6.
There has to be some amount of flax that takes you over the limit though.
So, they tested 9 tablespoons and 15 tablespoons too.
Remember, we start to worry at around 20 to 40.
Three and a half teaspoons of raw high- cyanide ground flax on an empty stomach?
Hardly a blip.
Seven teaspoons at a time? Same thing.
Fourteen teaspoons, which is four and a half tablespoons, and there's that 6.
OK, but what about a little over 9 tablespoons—
that's over a half cup at a time— and that does start skirting toxicity.
And finally, what about a whole cup?
I don't even know how you'd eat a whole cup at once,
but that is too much, putting you in that potential toxic range
for about three hours.
So much for the industry's 8 cups at a time are safe.
But even in this worst-case scenario situation, one cup raw
on an empty stomach at the highest dose they could find,
that person still didn't actually have any clinical symptoms.
This is consistent with the fact that there's not a single published report
of cyanide poisoning after consumption of flaxseeds anywhere in the literature,
even from Swedish health spas,
where they evidently give up to 12 tablespoons as a fiber shock.
Usually high doses are like two or so tablespoons three times a day,
and this dose would be safe with respect to possible acute toxicity of cyanide.
OK, but what about any possible chronic toxicity?
The World Health Organization has something called
a PMTDI, the provisional maximum tolerable daily intake.
It's defined as the amount you can eat safely, every day,
for the rest of your life, without risking any adverse
health effects, based on the best available data,
though often that's just like rat studies as it was in this case.
If you put varying doses of cyanide in the drinking water of rats
for a few months, at a certain level, the so-called benchmark dose
lower confidence limit, there's a 10% increased incidence
of the shrinkage of the tail of the epididymis, which is where
sperm is stored in the testicles.
That happens at the human equivalent of about 150 tablespoons
of flaxseeds a day worth of cyanide.
But they want to err on the side of caution,
so they introduce a 100-fold uncertainty factor to create the PMTDI.
So instead of 150 tablespoons of flaxseeds a day,
the average American should stick to under 1.5 tablespoons a day,
if you're going to eat them every day.
So my tablespoon-a-day Daily Dozen recommendation should be safe
by any of these standards.