A cat cannot taste sugar
Cats lack a working sweet receptor. The Tas1r2 gene that encodes one half of it is a pseudogene in all felids tested.
Established2 min read
The mammalian sweet receptor is a pair of proteins, T1R2 and T1R3. In the domestic cat, and in tiger, cheetah, and close kin, Tas1r2 is littered with stop codons. It does not make the protein. Behaviour matches: cats do not prefer sugar water to water.
They taste amino acids, bitter compounds, and some nucleotides — the chemistry of meat. Sweet was information about fruit and sap. A lineage that does not eat those lost the detector and did not grow it back. The indifference is genetic, not aloofness.
Caveats
- Some commercial foods still contain carbohydrate. Cats can digest a limited amount. They do not taste it as sweet.
- A few individual behavioural anecdotes do not resurrect the receptor.
Sources
- 1Li X. et al.. Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar. PLOS Genetics 1, 2005.