Acts as an electrogenic sodium (Na(+)) and chloride (Cl-)-dependent sodium-coupled solute transporter, including transport of monocarboxylates (short-chain fatty acids including L-lactate, D-lactate, pyruvate, acetate, propionate, valerate and butyrate), lactate, mocarboxylate drugs (nicotinate, benzoate, salicylate and 5-aminosalicylate) and ketone bodies (beta-D-hydroxybutyrate, acetoacetate and alpha-ketoisocaproate), with a Na(+):substrate stoichiometry of between 4:1 and 2:1. Catalyzes passive carrier mediated diffusion of iodide. Mediates iodide transport from the thyrocyte into the colloid lumen through the apical membrane. May be responsible for the absorption of D-lactate and monocarboxylate drugs from the intestinal tract. May play a critical role in the entry of L-lactate and ketone bodies into neurons by a process driven by an electrochemical Na(+) gradient and hence contribute to the maintenance of the energy status and function of neurons. Restricted to the apical cell membrane of enterocytes. Expressed in brain, colon, kidney and in the ileum and jejunum of small intestine. In the kidney, expression occurred in the proximal tubule and the loop of Henle, being restricted to tubular epithelial cells in both the cortex and the medulla. In the colon, predominantly expressed in the distal half of the large bowel and in the most terminal ileum. Localized selectively in the luminal surface of crypts in the large intestine and to the brush border in the middle parts of crypts in the cecum. In the brain, expression was seen throughout, exclusively in neurons, including the cortex, hippocampus, cerebellum and pituitary gland (at protein level). Expression is reduced in oligodendrogliomas. Transport of D-lactate and pyruvate stimulated by alpha-cyano-4-hydroxycinnamic acid, but inhibited by the short-chain fatty acids acetate, propionate and butyrate. Belongs to the sodium:solute symporter (SSF) (TC 2.A.21) family.