Thiamine (vitamin B1) belongs to the group of water-soluble vitamins. It is not stored in a cat's body in sufficient amounts, so it must be provided regularly through food. This prevents the body's entire reserve, which becomes depleted within a matter of days, from being used up. Not all forms of thiamine in the body have been thoroughly studied, but some commercial cat foods have been recalled because they contained too little of it, underscoring the importance of this vitamin.
What role does thiamine play?
Thiamine is a vitamin of great importance in a cat's diet, and its deficiency can lead to serious, often permanent health consequences. In the form of TDP (thiamine diphosphate), it is involved in carbohydrate metabolism and nucleotide synthesis. It is also responsible for the proper functioning of the nervous system, probably in both its free form and forms bound to phosphate groups.
Which foods contain it?
Cats do not synthesize thiamine, so it must be supplied through their food. Their daily requirement has been found to be two to four times higher than that of dogs. This is related to metabolism, although the exact reasons for these differences are not yet understood. The main sources of thiamine in a BARF diet are beef, poultry, and lamb hearts. Somewhat smaller amounts are found in pork, liver, egg yolks, and brewer's yeast. Particular care is needed when feeding raw fish of certain species, such as carp, herring, or mackerel. They contain an enzyme called thiaminase, which breaks down thiamine. Excessive consumption of these fish can therefore cause a deficiency. This can be avoided by choosing fish without thiaminase (e.g. salmon, trout, cod, or halibut) or by cooking the fish. Freezing does not inactivate thiaminase.
What about cooking?
Cooking causes losses of vitamin B1 because it is sensitive to high temperatures. The amount of thiamine lost depends on the temperature, duration, and method of cooking. Some may leach into the cooking liquid, so it is worth keeping the liquid and adding it to the bowl. All of this, in addition to the requirement values from FEDIAF and NRC, must be taken into account when determining how much thiamine to include in your cat's meal.
How can deficiency be prevented?
Thiamine is not stored in the body in sufficient amounts, and any excess is excreted in the urine. The most important way to prevent deficiency is therefore to provide it regularly through food. With a homemade diet, it is also worth paying attention to antithiamine compounds (thiamine antagonists) in individual ingredients. They alter thiamine's chemical structure and consequently deactivate it. They can be either synthetic or naturally occurring. Such compounds include thiaminases, which are enzymes. As mentioned above, they occur in some fish, as well as in certain crustaceans and bacteria. Their sensitivity to heat varies, so even after cooking we cannot always be certain that they are 100% inactive, and regularly feeding such foods can result in thiamine deficiency. Sulfur compounds, in turn, convert thiamine into thiamine disulfide, which has poor bioavailability, so meat preserved with sulfites should be treated with caution. Studies have found that dietary proteins and fats reduce the metabolic requirement for vitamin B1 more than carbohydrates do. This is likely related to thiamine's role in carbohydrate metabolism and the increased need for it in the Krebs cycle (during the catabolism of dietary carbohydrates). A cat also fails to receive the recommended regular dose of thiamine when its overall food intake decreases, for example because of anorexia or hyporexia. Symptoms of thiamine deficiency include loss of vision, dilated pupils that do not respond to light, impaired coordination, head tilt, ataxia, seizures, reduced appetite, and lethargy. Laboratory studies have also shown tissue-level changes, such as necrosis within brain tissue and hemorrhages at the periphery.
Excess thiamine
With a natural, well-balanced BARF diet, your cat is not at risk of excess thiamine. Any surplus is continuously filtered by the kidneys and excreted in the urine.
Sources
- Moon, S.-J., Kang, M.-H., & Park, H.-M. (2013). Clinical signs, MRI features, and outcomes of two cats with thiamine deficiency secondary to diet change. Journal of Veterinary Science, 14(4), 499–502.
- Kritikos, G., Parr, J. M., & Verbrugghe, A. (2017). The role of thiamine and effects of deficiency in dogs and cats. Veterinary Sciences, 4(4), Article 59.
- National Research Council (2006). Nutrient Requirements of Dogs and Cats, ch. 6. National Academies Press.
- Hilker DM, Peter OF (1966). Thiaminase in Fishery Products: A Review.