This GI issue involves the multi vitamin transporter. This is why
I suggested to you to space your biotin at another time of day.

I have yet to understand this transporter .. try using it as a search keyword on Google. I am on a small tablet and can't do this easily
currently.

I'm reading about the SMVT (sodium-dependent multi vitamin transporter), and I might as well be reading Chinese for all I'm understanding.

Tried reading through one research article that was focused on biotin and the SMVT, and at the end, it effectively said, "Yeah, we don't understand the body's biotin requirements very well."

Sorry to be dense, but I'm not understanding the spacing thing. I tried re-reading past discussion, but must have missed it.

I did most of my searching a few years ago about the MV transporter. We had a poster here who used ALA and B5 alot every day, and so I did find that link to biotin also being unable to be absorbed or transported in the GI tract, when the transporter is filled.

After some searching for you, I found that Iodide has been added.

All of the supplements seem to be microgram quantities in food.
In fact, ALA is almost non existent from food sources.

So the logic follows for me at least, that in order to get good biotin absorption and transport, the others should not be in high doses. Just 100mg of ALA which is a small dose compared to the studies for neuropathy which are hundreds of milligrams, would overwhelm this transporter.

So you could try just not using the R-lipoic acid at all for a month, and see if you note any changes? That might open up the transporter to move your biotin to the tissues better?

Adding a bit to what mrsD wrote:

The MV transporter can only transport one of its substrates (iodide, biotin, lipoate and pantothenate) at a time. It can not transport any two of them (eg, biotin and lipoate) at the same time.

What this means is that all of its substrates are what are called competitive inhibitors of each other. This means that relatively high concentrations of any of its other substrates will inhibit transport of biotin.

So, as mrsD suggested, discontinuing lipoate for a while is worth a try to see if you notice any improvements. That way lipoate is less likely to act as a competitive inhibitor of biotin transport.

Thank you both! Got it now.

The reason I started taking R-Lipoic Acid back in 2014 was that a nutritional test done by an int. medicine doctor showed I was borderline low on it. The doc suggested supplementing. Regardless, I'll give it a shot.

I'm also digging into the genetics of the involved SCL5A6 gene. I'm having a tough time finding information, but it looks like I do have a couple of homozygous variants.

I read an article recently that discussed lipoic acid/lipoate.

Let me see if I can find it again.....

nope, but I did find this:

Top 1 List of Foods High In Alpha Lipoic Acid (ALA)

So this link illustrates how tiny the amounts of ALA are in most foods. This is why lipoic acid needs that transporter. Even when using small supplement amounts of milligrams it becomes a rather change to "drug" status of lipoic acid. The article I read a while back called the use of lipoic acid a therapeutic drug use and not a vitamin supplement use. So evolution did not occur with high lipoic acid consumption as we see today, with its use for diabetic neuropathy. Lipoic acid is made by our own body's metabolism.

Also the addition of iodide to the task of the MVtransporter explains the hypothyroid risk of using high dose lipoic acid since the transporter carries iodides (also in microgram quantities);
Iodides were not on the list in the past. And I expect other microgram quantities of nutrients to perhaps be found to need a transporter in the future.

When searching this topic try these 3 keywords...
1) lipoic acid
2) thiotic acid (often found in research articles)
3) lipoate

All are found in many papers.

Thanks very much for all this, MrsD. I plan on doing a lot of reading this weekend.

Spinach is a staple for me, BTW. Rarely a day goes by.