In my Daily Dozen checklist,
I recommend eating one tablespoon of flaxseed a day.
But you may have heard that flaxseed contains cyanide.
What?!
Is it anything to worry about? Watch the video to find out.
"How Well Does Cooking Destroy Cyanide in Flax Seeds and Should We Be Concerned?"
Sweden's dietary guidelines are pioneering in many ways;
for example, encouraging people to decrease their climate impact
by choosing more plant-based foods, which tend to produce greatly
fewer greenhouse gas emissions. But I was surprised by this page
on the official Swedish National Food Agency website,
which translates to cyanogenic glycosides and hydrogen cyanide,
encouraging people to stay away from ground flaxseed
for fear of cyanide toxicity, as in the ground flax seeds
I encourage everyone to eat every day.
You can see why this was the first question I got
when I spoke in Stockholm.
Was the Swedish government on to something?
Had I just been duped by Big Flax-funded researchers
who claimed you could eat pounds of ground flaxseeds a day without worrying,
more than 150 tablespoons a day? First, some background.
As many as one in five plants that we eat produce cyanide.
In fact, if you look at the major food crops in the world,
more than half are cyanogenic, meaning cyanide producing.
See, unlike toxic elements like lead, mercury, arsenic that can't be broken
down into anything, cyanide is an organic molecule:
one carbon atom attached to one nitrogen atom.
In this state it can definitely be toxic,
but broken down or complexed to something else and it loses its toxicity.
And we have an enzyme in our body that does just that,
a cyanide detoxifying enzyme.
And that's just one of five main ways our body can detoxify cyanide.
It does require protein to do it though, and so that's why you can read about
chronic cyanide toxicity among malnourished populations in Africa
trying to live off of improperly processed cassava root.
But as long as we're getting adequate protein in our diet,
our body can detoxify the normal amounts of cyanide we eat every day.
Now there is a rare, congenital genetic condition called Leber's disease,
where you're born without the ability to detoxify cyanide.
And indeed, yeah, you could go blind drinking apple cider or something,
but otherwise our bodies evolved to be cyanide-detoxifying machines,
but obviously there's a limit.
For example, a case of cyanide poisoning after bitter almond ingestion.
Not regular almonds, which produce about 40 times less cyanide,
but bitter almonds, which you can't even buy—they're used in flavor manufacturing—
but if you did, eating 50 of them could kill you,
or even just a handful for a small child.
This suggests that eating 2,000 regular almonds at one sitting
could also be bad news.
You can't buy bitter almonds, but you can buy apricots,
and apricot kernels, which are the seeds inside the stone, actually have
pretty toxic levels, and have indeed been implicated in cases
of severe cyanide poisoning, all linked to the
"Laetrile: cult of cyanide, Promoting poison for profit"
that I talked about previously.
So I'm totally sympathetic to regulators wanting to take a precautionary approach.
But are flaxseeds like bitter almonds, where just a few ounces could kill you,
or more like regular almonds where regular dietary intake
wouldn't even come close?
Although the fact that flaxseeds can produce cyanide sounds like
it would be a significant health concern,
it is not for several reasons, says flax industry-funded scientists.
First, the adult human body has the ability to detoxify
up to 100 mg of cyanide per day. That's where they come up with
their "pounds of flaxseeds a day are safe" number.
And if you wanted to eat more than
those totally unrealistic 150 tablespoons a day,
you could just eat them in baked goods since cooking destroys the cyanide.
And eating 7 or 8 tablespoons of raw doesn't even bump
urinary thiocyanate levels, which is an indicator of cyanide exposure,
so it doesn't even look like your body is even exposed to it.
Thus, the toxicity of flaxseed from cyanogenic glycosides
is not, evidently, a realistic health threat.
OK, let's unpack that.
The cooking part is mostly true. Yes, bake muffins with even
like a quarter cup of ground flax each for 15 to 18 minutes
at about 450 degrees Fahrenheit and the cyanide-forming compounds are gone.
Looks like the same thing happens with baked bread.
But bake ground flax seeds on their own, and even an hour at 350
only wipes out 20%, though baking them whole wipes out 80%.
And what, baking in bread or muffins wipes out 100%?
How does that make any sense?
It's the moisture.
It's heat plus water that wipes out the cyanide.
Boiling for just five minutes can wipe it out, like when making
hot cereal or something.
And so, yes, it's true in most cases
that cooking eliminates the cyanide compounds
because it typically starts out in a batter as an egg substitute,
or baking crackers, or the dough starts out moist.
And so, yes, in those cases the cyanide is gone upon cooking.
But you can't just spread ground flaxseeds on a baking sheet
because they dry out so fast that only a minority of the cyanide is lost.
But, look, why does it matter if your body
doesn't even seem to notice 7 or 8 tablespoons of raw?
But that's not true.
Urinary thiocyanate excretion doubled at that level,
though that's just a sign your body is actively detoxifying it.
And if we can detoxify a kilo worth of flax a day, what's the problem?
Well, look, even if the adult human body has the ability to detoxify
up to 100 mg of cyanide a day, first of all, look, kids eat flax too.
Second of all, a kilo has more than the 100 you said we could detoxify,
about 50% more.
And I'm not interested in how much we can detoxify "up to."
For safety you're interested in the worst-case scenario,
not the best-case scenario.
Would someone please just give people different doses of flaxseeds
and just measure how much cyanide ends up in their blood?
But that's never been done until now, which we'll cover next.
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.