Ordinary Salt - photo by parl (creative commons license)
People search for low sodium cat food. Why? Sodium is short for sodium chloride = salt in common parlance. Most of us have heard about salt and our health. The "experts" are always telling us to restrict salt intake. This is because it is thought that too much salt raises blood pressure, generates greater retention of water (swollen ankles), aggravates the thinning of bones and is related to kidney disease and asthma (/www.davidgregory.org). Is it the same for cats? Cats do have a similar anatomy to humans.
Dr. Hodgkins DVM says that foods made for cats with heart disease restrict protein and salt. This then tallies with the benefits of low salt for people with high blood pressure (the pressure of the blood against the artery walls). (note: high blood pressure in people can be caused by high salt intake).
However Dr. Hodgkins DVM does say that a restriction on the amount of salt in a cat's diet may not be necessary. It just depends and a vet will advise. But don't buy the cat food that the vet sells as the advice is probably tainted by financial profit.
One way to make a low sodium cat food diet is to mix in salt-less protein to regular canned or canned food for cats with heart problems.
A good source of salt and phosphorus free protein is cooked egg white. A cat might not like a low salt diet however.
Sometimes vets recommend that cats with chronic kidney disease should eat low sodium cat food. Not all experts agree with this, however.
Kattavit Low Natrium Cat Food - a UK product or available in the UK (what is "natrium"?) is for cats who suffer from heart or liver diseases.
It seems that the following cat foods have some of the lowest levels of salt in canned foods: IVD Modified canned (0.2% sodium), Wysong Senior, Wysong Maintenance, Wysong Vitality (all Wsong = 0.1% sodium).
For dry foods these are low sodium cat foods: Royal Canin Renal LP dry, Innova Cat Lite, Wysong Health Biscuits, Wysong Anergen, Wysong Vegan, Wysong Synorgon, Hill's K/D, IVD Modified dry, IVD Mature dry. The food in bold has the lowest level of sodium (source for low sodium food - but please make your own checks).
Note that the low salt diets are associated with kidney disease and old cats. It seems that old cats, as is the case for old people, have an increased likelihood of heart disease.
The Washington State University College of Veterinary Medicine states that a diet reduced in salt is recommended for cats with heart failure. A lot of cat food contains high salt levels.
For moderate salt restriction they cite Science Diet Senior, Hills K/D and Purina CNM NF as examples of cat suitable cat food.
For higher levels of salt restriction these food are recommended: Hill’s H/D, Purina CNM Canine CV-Formula, Hill’s Healthblend Canine Geriatric, Waltham low sodium and Purina CNM Feline NF-Formula (of course these are US products some of which or the equivalent might be available in the UK or elsewhere).