Define Vitamins B₁₂ Deficiency in Vegans?

Because plants do not synthesize vitamin B₁₂, individuals who consume diets completely free of animal products (vegan diets) are at risk of vitamin B₁₂ deficiency. This is not true of lacto-ovo vegetarians, who consume the vitamin through eggs, milk and other dairy products.

Persons living exclusively on vegetarian diets (vegans) have low serum levels of vitamin B₁₂ and develop specific symptoms such as sore tongue, paraesthesia and signs of degeneration of the long tracts of the spinal cord as a result of low intakes of vitamin B₁₂. Megaloblastic anaemia is not so common when folic acid intake is adequate. The anaemia results from decreased DNA synthesis and failure of the cells to divide properly, coupled with the continued formation of RNA.