Found in the blood and in the fluid that surrounds cells, sodium maintains the cellular environment and prevents cells from swelling or dehydrating. Sodium is also important for maintaining proper nerve and muscle cell function.
Meat, poultry, fish, and eggs are good sources of sodium.
Sodium also might be included in commercial pet foods in the form of table salt (sometimes listed on the ingredient panel as salt). Salt is an important palatant for animals, as well as for people.
The Association of American Feed Control Officials recommends that dry dog foods contain at least 0.3% sodium for both maintenance and to support normal growth and development. This is the minimum recommended levels.
While high sodium intake might cause increased thirst and water consumption, the extra sodium is excreted in the urine of dogs. Healthy dogs are able to consume diets with higher sodium levels than those found in most commercial pet foods without increased blood pressure or gain in body water.
Therefore, the sodium level in commercial pet foods is not a cause for concern in healthy animals.

A veterinarian might recommend decreasing a dog's sodium intake if the animal has some types of kidney, liver, or heart disease, in order to help decrease high blood pressure or the accumulation of excessive body fluid.
Although older dogs might be more likely to develop these diseases, healthy older dogs do not require a low- or reduced-sodium diet.
The sodium level in our dog foods is appropriate for a healthy dog. The sodium content in these foods is balanced in proper proportions with energy, other minerals, vitamins, fats, proteins, and carbohydrates.
It depends on the breed of dog, but your pet's senior years generally begin at age 7. Louise Murray, DVM, director of the ASPCA's Bergh Memorial Animal Hospital in New York City and author of Vet Confidential (Ballantine, 2008), tells you what you need to know to keep your older dog spry and happy.
At this stage, Murray recommends taking your dog to the vet twice a year. 'So much can happen to an elderly dog,' she says. Your veterinarian can take blood annually to test liver and kidney functions. 'Discovering problems early is extremely important,' she says. Your vet can be on the lookout for conditions that often affect older dogs, such as anemia and arthritis.
Pay attention to what might be subtle changes in your dog's habits: Is she drinking more water or urinating larger amounts? These behaviors might indicate a liver or kidney problem. Have your dog's bowel movements shifted? This could indicate a digestive issue. Diabetes or digestive problems might cause your dog to eat more but still lose weight. Knowing the dog's patterns can help the veterinarian determine a course of treatment.
Continue to use preventive medicines.
Clean your dog's teeth daily. If she has tartar buildup, you might need to have her teeth professionally cleaned at your vet's office, which requires sedating your pet.
Your dog is probably less active, so steady, moderate exercise is best for her now. Don't turn her into a 'weekend warrior' who, after lying around on weekdays, accompanies you on a 10-mile hike on Saturdays. This is especially hard on an older dog's joints.
Your veterinarian might wish to put your dog on a senior diet, such as IAMS™ ProActive Health™ Senior Plus. These formulations contain nutrients specifically geared toward older-dog health.