Methylcobalamin (B12) vs Thiamine (Benfotiamine)

Mechanism

Methylcobalamin serves as a cofactor for methionine synthase, transferring a methyl group from 5-MTHF to homocysteine to regenerate methionine and subsequently SAMe. Adenosylcobalamin (the other active B12 form) is a cofactor for methylmalonyl-CoA mutase in mitochondrial energy production and odd-chain fatty acid metabolism. B12 is essential for myelin synthesis, DNA synthesis (thymidylate synthase pathway), red blood cell maturation, and neurological function. Deficiency causes megaloblastic anemia and irreversible subacute combined degeneration of the spinal cord.

Standard Dosing

1000-5000 mcg methylcobalamin daily (sublingual preferred)

Timing

Morning, sublingual for best absorption (bypasses intrinsic factor requirement). Can combine with methylfolate.

Cycle Duration

ongoing

Side Effects

• Acne/skin breakouts (common)
• Anxiety (overmethylation in susceptible individuals)
• Diarrhea
• Headache
• Hypokalemia (during rapid repletion of severe deficiency)

Contraindications

• Leber's hereditary optic neuropathy (cyanocobalamin specifically; methylcobalamin is generally safer)
• Polycythemia vera

Best Stacking Partners

Mechanism

Benfotiamine is a lipophilic S-acyl derivative of thiamine with 5x greater bioavailability than water-soluble thiamine. Once absorbed, it is converted to thiamine pyrophosphate (TPP), the active coenzyme for pyruvate dehydrogenase (linking glycolysis to Krebs cycle), alpha-ketoglutarate dehydrogenase (Krebs cycle), branched-chain alpha-ketoacid dehydrogenase (BCAA metabolism), and transketolase (pentose phosphate pathway). Benfotiamine specifically activates transketolase, shunting glucose metabolites away from damaging AGE (advanced glycation end-product) formation pathways, hexosamine pathway, and PKC activation — the three major pathways of hyperglycemic damage.

Standard Dosing

150-300mg benfotiamine daily

Timing

With meals. Divide higher doses.

Cycle Duration

ongoing

Side Effects

• Generally very well tolerated
• Mild GI upset (rare)
• Skin rash (very rare)
• Garlic-like body odor at very high doses

Contraindications

• Rare thiamine allergy (more relevant to parenteral administration)

Best Stacking Partners