Hey Guys!
OK, yes, this can seem to be a bit complex, but if you take a few seconds to look at this figure it might help:
If you're really interested, and this sounds like I'm trying to be a shill, but the article isn't mine to advertise as I wrote it for John's site, I would check out the article I wrote for mountaindogdiet (or at least listen to the two podcasts that have been posted here or in another thread I just posted in where I cover the topic.)
[IMPORTANT - Just above, some folks are talking ORAL doses along the lines of
grams, e.g, 2 vs 3g and others are talking about injecting hundreds of
milligrams, so that's some of the confusion in the last few posts above.
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Does L-Carnitine help with fat oxidation?... Yes.
Does L-Carnitine (potentially, at some does) have a negative effect on thyroid hormone action? Yes.
We don't have an exact
dose-response curve, e.g., to see what happens when you progressively increase L-Carnitine (and the stores take some time to build up / deplete) in terms of whatever slowing of metabolism would occur.
So, this dose-response curve would be
time dependent given the time it takes to increase / degrees L-Carnitine and the route of administration (oral / injectible/ injectible with lots of carbs/ insulin), so this adds another complicating factor.
For example, A given higher end oral dose (e.g., 4 grams orally) might take
weeks to build up over the course of a diet and at that point then, when deeper in the diet, someone might find they would also tend to reach for T3 or T4 anyway. In the case of a high L-Carn dose, they could potentially use the T3
earlier or feel they need
more (base on resting HR, morning temperature, how the diet is going in terms of fat loss), than when the NOT using L-CARN in the diet (BECAUSE the L-Carn is limiting thyroid action to some degree).
---> THE ABOVE is what I've heard from a few guys now: with L-Carn (or higher L-Carn supplementation ) they ended up using more T3 than in previous diets.
ANOTHER EXAMPLE could be - this is one I just heard from a guy who's recently been on the Olympia stage - that when using both L-CARN (no Thyroid used in this case, but this person has a Juan Morel level metabolism - no, it's not Juan!) and when the L-CARN was removed deep in the prep, between shows, the competitor started dropping size, which could be explained by
releasing the L-CARN brake on his metabolism. In other words, for him, his very active / responsive thyroid makes adding / holding size difficult and inadvertently the L-Carn was slowing his metabolism, which became evident when he removed the L-Carn.
NOTE HERE (See the figure linked above) that 1.) elevated T-3 (being hyperthyroid) will deplete L-Carnitine, whereas 2.) adequate T-3 is necessary for adequate ENDOGENOUS L-Carn production (hypothyroidism would / could mean reduced L-carnitine stores, or at least less endogenous production).
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So, 1.) if you're running high T3, you might be low in L-Carn (this is likely
variable like damn near everything) and
benefit by ADDING L-Carn.
OTOH, 2. ) if you're low on T3, d/t your diet, and not running T3, this means your L-Carn stores may be low (depending also on diet), so
adding it could help with fat loss.
So in both those cases, L-Carnitine HELPS! LOL!
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So, we've got these two molecules playing off and interact with one another in an intricate (cool as shit) way in the unenhanced, non-supplemented situation (along with of the possibility, too that exogenous L-Carn in the diet can be affecting this interplay).
THEN, when you consider what we're talking about:
1.)
Artificially elevated L-Carn by
injecting it (with insulin) a/r taking
"massive" supplemental oral doses (relative to what you could eat in most circumstances) Plus
2.) Using
exogenous thyroid sources that can make you hyperthyroid (perhaps to match being "hypercarnitine").
3.) That the impact of L-Carn on Thyroid ACTION does not manifest clearly in
bloodwork (and I'd love to find some mechanistic data on this, as it suggests non-nuclear regulation of the thyroid axis in terms of feedback inhibition, etc.)
You've got something I figure those of us who might be using L-Carn, T3 (or T4) and checking bloodwork, might want to know about.
And yes, I've seen L-Carn work well for folks for sure, so I'm not saying it can't be used effectively of course. (I've used it and had clients use it.) This is just info. that can perhaps for some better inform their use in case they are tripped in a vicious cycle of adding more and more of each and not dropping fat, or decide to remove L-Carn (if they have trouble holding size when at very low BF%) .
-Scott
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