Vitamin B12

Vitamin B12 is a nutrient that Ray Peat considered largely unnecessary to supplement for most people who consume animal products, because intestinal bacteria synthesize it endogenously. 3 He noted that individuals with small intestine inflammation (SIBO) can even have B12 levels 50% higher than normal due to bacterial overgrowth in the wrong location. 3 Georgi Dinkov has extended this view, arguing that the only people who genuinely need vitamin B12 are those with the specific disease pernicious anemia, and that for the majority of the population, there is no need for extra intake. 6

Peat acknowledged that the methylcobalamin form of B12 contains a methyl group, but he considered the quantity so tiny that adverse reactions are more likely allergic in nature rather than a consequence of methyl donor overload. 2 He cautioned that synthetic vitamins are often made with somewhat contaminated chemicals and can be allergenic, with B2 and folic acid being the worst offenders for allergies, while B1, pantothenic acid, niacinamide, and B6 are relatively safe. 2 Dinkov has pointed to a more specific risk, citing studies that link high levels of vitamin B12 with several kinds of cancer, especially of the colon, liver, and pancreas, which is why he deliberately omits it from his B-complex formulations. 6

In the context of metabolism, B12 plays a recognized role in the methylation pathway, which is involved in processing the amino acid methionine and eliminating homocysteine, a compound that can have negative effects on the vasculature. 7 This pathway, which also requires B6 and B2, is crucial for making creatine, the myelin coating of nerves, and DNA. 7 A deficiency in B12 or other methyl donors is associated with a demyelinating condition called subacute combined degeneration, which ties the methylation pathway to the integrity of white matter in the brain. 8 However, Danny Roddy has questioned whether a person eating a high-protein diet could realistically become deficient in methionine, suggesting the body's priority is to shunt available methionine toward critical functions like myelin maintenance before using it for hair growth. 8

Peat’s broader nutritional philosophy emphasized obtaining B vitamins from food rather than supplements, recommending eggs and liver as the easiest way to get both trace minerals and vitamins. 1 He observed that traditional diets were nutritionally complex and included hormone-rich glandular tissues, contrasting with the modern reliance on isolated synthetic vitamins. 4 Dinkov reinforces this by criticizing standard B-complex supplements that indiscriminately include all B vitamins in uniform doses, such as 50 or 100 milligrams each, which he sees as lacking a physiological rationale. 6 The core bioenergetic function of the B vitamin group is to act as cofactors for the enzymes that convert food into energy, with deficiencies causing an energetic deficit that prevents the complete oxidation of glucose and promotes the storage of electrons as fat. 9