[Rhonda]: You made a pretty important point for people and that is that the myrosinase
enzyme is heat-sensitive and as you pointed out, most people like to cook their cauliflower
and broccoli or slightly steam it and their trade-off for that is maybe it tastes a little
better, but also it inactivates the myrosinase enzyme.
[Jed]: Correct.
[Rhonda]: So they're not actually getting as much sulforaphane from the glucoraphanin
as they would have if they were to just chew on that raw broccoli.
But what about the myrosinase enzyme?
Is the stability the same throughout all the cruciferous family?
So, like, if you look at the broccoli sprouts versus the mature broccoli or kale?
[Jed]: So myrosinase appears to be about as stable throughout the family.
There are differences, subtle differences to the protein composition of myrosinase.
This is in different cruciferous vegetables, to be sure.
Subtle enough so that I can’t even describe them to you.
I mean, they're minor differences, but they certainly must confer increased or decreased
stability or catalytic ability on those molecules.
Interestingly, if you ingest glucoraphanin or glucosinolates without myrosinase at all,
you then can count on the bacteria in your gut, in your intestines, primarily, to make
that conversion.
And sometimes scientists think they're so darn smart.
Just to back up just a little bit, we observed that when you delivered just glucoraphanin
to people, just give them one dose, one reasonable amount that which they would get in a serving
of broccoli, and then we collected their urine for 24 hours.
We asked them to collect their urine for 24 hours, so you get a full 24-hour collection
which pretty much spans the period during which the enzyme myrosinase acts, sulforaphane
goes into cells, gets recognized, turns on Nrf2, gets spit back out, and then gets excreted
in the urine.
So by collecting a 24-hour urine, we can get a very good idea of how much bioavailability
there is, how much metabolism and availability.
And it turns out that if we looked at 100 different people, and we did, after giving
them one dose of glucoraphanin, their bioavailability, the amount they gave back to us in their urine
was all over the map.
It ranged from very, very little, but always something to 40% or 50%, or even 60% or 70%
of what we gave them.
But the mean was pretty low.
It was about 10%.
So most people converted, and metabolized, and excreted only about 10% of what they were
given.
So, when you give sulforaphane itself, the end product, the active ingredient, if you
will, we get more, like, 70%, 75%, 80% bioavailability.
Still a bit of variability person-to-person, but since we're up sort of near maximum, it
appeared to be not as great.
Well, it was not as great in terms of a percent of the whole.
So that sounds a little convoluted.
But essentially most sulforaphane came back at us in the urine and was available.
So, in our infinite wisdom, we thought if we co-deliver myrosinase, if we give these
people active myrosinase in addition to glucoraphanin, they're all going to give back 70% to 90%
of the metabolites and we'll get rid of the variability person-to-person.
Didn't happen that way.
[Rhonda]: Really?
[Jed]: Really.
It didn't happen that way.
What did happen is that we moved the bar up so that instead of 10% bioavailability for
70%, we had about 35% or 40%.
So the average moved up substantially.
It was about three or four times more, but there was still quite large person-to-person
variability.
So we have to sort of step back a little bit and say, "Yes, this is due to intrinsic myrosinase
activity in the gut because certainly, we hadn't done anything to get rid of that.
That was still acting on these molecules.
But also just innate mammalian genetics, differences between you and me and the way we process
these metabolites once they're formed, differences in absorption, differences in distribution,
in metabolism.
So there's a lot we still don't know.
There's a whole lot we still don't know.
But as a result of this sort of cocky thinking that we could abolish this variability and
at least have a very predictable amount delivered to people, we did learn that we can greatly
increase bioavailability by delivering it with myrosinase.
And, in fact, there are now companies that are selling glucoraphanin plus myrosinase.
You have to be careful if you buy those supplements because it's not a given that they're going
to be as stable as multivitamins and things that you can just leave on the shelf for years.
So you need to pay attention to the expiration dates on those products that have live active
enzyme.