nick's Avatar


14 Mar, 2011 09:14 AM

Hi Purebulk
I want to buy glycine in bulk.
My questions.....
1. I've read, maybe incorrectly, that glycine doesn't cross the blood-brain barrier very well. Your detailed product info states it "readily crosses the blood-brain barrier". Can you clarify with any references, would appreciate this support.
2. Are L-glycine and glycine the same product?
3.How does USP grade compare to pharmaceutical grade?
Also, I've read d-serine and sarcosine (glycine agonists) are even more effective but can't see where to buy.

  1. Support Staff 1 Posted by James Coffey on 17 Mar, 2011 11:44 PM

    James Coffey's Avatar


    Your questions:

    Q1: I've read, maybe incorrectly, that glycine doesn't cross the blood-brain barrier very well.


    "Although other researchers using glycine for brain disorders have reported that such small doses of glycine would not be sufficient to cross the blood-brain barrier,1 measurements of amino acids in the cerebrospinal fluid during the above study suggest that it did enter the brain. However, there are potential concerns that high-dose glycine could increase stroke damage."

    Q2: Are L-glycine and glycine the same product?
    A2: The naturally occurring forms of amino acids are typically the “L form”, as in L-arginine, L-cysteine, etc. Synthetic forms are denoted as “D or DL forms”, such as DL-Methionine and D-Aspartic Acid. But there are 2 amino acids that have only one form without these variations: Glycine and Taurine. These two aminos are sometimes called L-Taurine or L-Glycine, but are more properly called just “Taurine” and “Glycine”. Regardless of the name used, they are always natural amino acids.

    Technical explanation:

    Most amino acids have a property that, when the molecule is put into a solution, it will polarize and rotate light either to the left or right. The Greek words denoting left and right are Levo for left and Dextro for right, so the letters L and D are used to distinguish these forms. This polarization and rotation of light is called “optical rotation”. The differing L and D forms are called stereoisomers. For amino acids that polarize light, the L form is the natural form.

    However, Taurine is an amino acid that does not polarize light. It thus is properly called just “Taurine”, without L or D configurations. While some label Taurine as “L-Taurine”, that name is not technically correct. “Taurine” is the same exact molecule and form as what is commonly mislabeled as “L-Taurine”.

    There is another amino acid that lacks a potential optical rotation. Glycine is a very simple molecule that comes only as “Glycine”, also lacking different L or D stereoisomer forms.

    The D forms of amino acids sold commercially are considered to be synthetic. However, D forms of amino acids are not always synthetic. There are several D forms that exist in nature. In addition, amino acids can be racemized by the body and go back and forth between the D form and the L form quite easily. However, only L forms can be incorporated into proteins. For the purposes of dietary supplements, the L forms are natural and the D forms are synthetic. DLPA and DL-methionine are actually racemic mixtures of both L and D forms.

    But there is no such thing as D-Taurine or D-Glycine; in other words, no synthetic forms exist of these two aminos since each only comes as one isomer that doesn’t polarize and rotate light to the right. Nor are there really L forms of these, since they do not polarize and rotate light to the left, either. There are simply single, natural isomers of just plain Glycine and Taurine.

    Don’t assume that all D or L forms of molecules are good or bad, since it really depends on the individual substance concerned. For example, the D isomers of vitamin E are the natural forms and the L isomers are synthetic; just the opposite of amino acids. Thus the terminology and forms of what is natural or synthetic will vary by substance. Some natural molecules exist as L form, some as D form and some have only one form, whether in food or if synthesized.

    Q3: How does USP grade compare to pharmaceutical grade?
    A3: USP is a pharmaceutical grade, but there are about a dozen internationally accepted pharmaceutical grades of which USP (United States Pharmacopoeia) is just one, i.e. USP BP EP JPL CP etc...


    Timothy McNulty
    PureBulk, Inc.
    1640 Austin Rd
    Roseburg, OR 97471

    T: 541-679-1500
    F: 213-226-4677
    email: [email blocked]

  2. James Coffey closed this discussion on 17 Mar, 2011 11:44 PM.

Comments are currently closed for this discussion. You can start a new one.

Keyboard shortcuts


? Show this help
ESC Blurs the current field

Comment Form

r Focus the comment reply box
^ + ↩ Submit the comment

You can use Command ⌘ instead of Control ^ on Mac