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Vitamin B12 (Cobalamin) in dog and cat diets

A short guide to the role of Vitamin B12 (Cobalamin) in dog and cat nutrition.

Vitamin B12 (Cobalamin)

It belongs to the water-soluble vitamins, but is the only one of them that can be stored in the liver. Its structure contains cobalt. It is essential for the formation of red blood cells (erythropoiesis), DNA synthesis, and building the myelin sheaths around nerves [1]. To be absorbed from the intestines, it must first bind to a transport protein (intrinsic factor). In the dog it is produced by the stomach and pancreas, in the cat — by the pancreas alone, which is why in the cat any pancreatic disease almost cuts off the absorption pathway for B12 [2].

Where it's found: Exclusively in products of animal origin: liver, kidneys, hearts, fish, egg yolks, and red meat. Beef liver contains about 40–60% more B12 than poultry liver — not every "5% liver" is equal [1].

Deficiency: Rarely results from diet alone — in a healthy animal with liver and kidneys in the bowl it is unlikely. Most often it has a disease basis: inflammatory bowel disease (IBD), pancreatic insufficiency, or bacterial overgrowth [3]. It leads to megaloblastic anemia (defective, oversized red blood cells), wasting, diarrhea, and neuropathy. In the cat a vicious circle forms: diseased intestines lower B12, and low B12 worsens loss of appetite and weight loss [2]. Note: here supplementation (often oral) is sometimes necessary, but it is conducted by a veterinarian based on testing [4].

Excess: Because it is a water-soluble vitamin, its excess is efficiently removed in the urine and dietary toxicity does not occur. It is worth knowing, however, that elevated B12 in the blood does not result from diet, but can be a marker of liver or neoplastic disease — it is a diagnostic signal for the veterinarian [5].

Sources

  1. National Research Council (2006). Nutrient Requirements of Dogs and Cats — Chapter 6, Water-Soluble Vitamins. National Academies Press. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
  2. Siani G, Mercaldo B, Alterisio MC, Di Loria A (2023). Vitamin B12 in Cats: Nutrition, Metabolism, and Disease. Animals 13(9):1474. https://doi.org/10.3390/ani13091474
  3. Kather S, Grützner N, Kook PH, Dengler F, Heilmann RM (2020). Review of cobalamin status and disorders of cobalamin metabolism in dogs. JVIM. https://doi.org/10.1111/jvim.15638
  4. Toresson L, Steiner JM, Suchodolski JS, Spillmann T (2016). Oral Cobalamin Supplementation in Dogs with Chronic Enteropathies and Hypocobalaminemia. JVIM. https://doi.org/10.1111/jvim.13797
  5. Trehy MR et al. (2014). Hypercobalaminaemia is associated with hepatic and neoplastic disease in cats: a cross sectional study. BMC Vet Res 10:175. https://doi.org/10.1186/s12917-014-0175-x
  6. Ruaux CG (2013). Cobalamin in companion animals: diagnostic marker, deficiency states and therapeutic implications. Vet J 196(2):145-52. https://doi.org/10.1016/j.tvjl.2013.01.025