Not all B-vitamins

The phrase "B-complex" on a supplement label hides enormous variation in quality. Cyanocobalamin and methylcobalamin are both technically vitamin B12 — but they behave very differently inside cells with MTHFR variants or low SAMe. The same is true for folic acid vs. 5-MTHF, pyridoxine vs. P5P, and D3 with or without its cofactor K2. The "form" of a nutrient often matters more than the milligram number on the label.

For people with genetic polymorphisms — MTHFR, MTR, MTRR — synthetic forms can actually compete with the bioactive forms at enzyme sites, slowing the very pathways the supplement is meant to support. For practitioners working with the nutrigenomically-informed patient, the default is to skip the synthetic versions entirely.

The articles below compare forms head-to-head and explain when each version is appropriate. Start with the folate and B12 guides, then work through the cofactors.