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This bypasses the skin barrier that limits topical absorption, allowing higher concentrations to reach the dermis and deeper tissue layers

PMID 25820384

However, absorption often declines with age and can be impaired by digestive conditions (such as IBS, Crohns, or coeliac disease) and by certain medications (for example, long-term use of proton pump inhibitors)

Nearly all studies originate from one research group, raising concerns about independent replication

A 1mL syringe typically has 100 units

Purity and a certificate of analysis matter more here than the lowest price on the page, because a clean sample is the starting point for any meaningful result