What About Low Sodium Diets in Dogs?

We humans are advised by our doctors to avoid high levels of salt in our diets, mainly because limiting intake of salt - or actually the sodium in table salt - can help avoid high blood pressure. A friend of mine, who is even older than I am, took this to heart. He is in excellent physical condition, plays 18 holes of golf 5 days a week, and follows a healthy (and delicious) diet. He is careful about his sodium intake, and takes his blood pressure medicine regularly. A few weeks ago he wound up in the hospital. His body ran low on sodium.

One of the blood pressure medicines my friend was taking works by increasing the elimination of sodium. He had also been working a lot in the yard, in the summer heat, and you lose sodium when you sweat. These things, together with his healthy low-salt diet, precipitated a trip to the emergency room. He recovered completely with treatment - IV fluids - and salt. (Dogs and cats have relatively few sweat glands and lose practically no salt from perspiration.)

High blood pressure is not as common in dogs and cats but they are both susceptible to bladder stones. One of the strategies that has been considered for prevention of bladder stones is a high salt diet. When your pet eats more salt, he drinks more water, urinates more, and this can help flush out the minerals that may cause stones.

A recent experiment done by veterinarians at the University of Tennessee and Hill's Pet Nutrition, Inc. took a closer look at side effects of feeding a high salt diet to cats. They found no significant bad effects on blood pressure, heart muscle, bone density, or the hormones they measured. And the low sodium diet did produce increased quantities of dilute urine.

But they also found that the high sodium diet had a deleterious effect on kidney function, especially in cats that already had early signs of kidney failure. Blood tests often show signs of early kidney failure in dogs and cats that have no symptoms of the disease. Because the high sodium diet was only fed for 12 weeks and cats were already showing laboratory evidence of kidney damage, the researchers concluded that a high sodium diet is probably not a good way to prevent bladder stones, at least in cats.

Another strategy for prevention of bladder stones is to feed a diet that has very low quantities of the minerals that cause stones. This works very well with "struvite" stones, one of the two most common types in dogs and cats. Twenty or thirty years ago struvite was by far the most common type of bladder stone in dogs and cats. Then pet food companies began offering special foods restricted in those minerals and veterinarians started prescribing it. Bladder stones are still about as common as they ever were, but now about half of bladder stones are the other type, "calcium oxalate." These can't be prevented very well by mineral restricted diets.

Every case is different and the risk of recurring bladder stones must be balanced against the benefits and risks of dietary changes and other medications. Your veterinarian can advise you what's best for your pet.

A man tries to do good by eating low salt diets, taking his blood pressure medicine, and doing the yard work like a good husband, and winds up in the hospital. Veterinarians try to prevent bladder stones in pets by prescribing special diets and wind up with other problems. Darned if you do and darned if you don't.