When I think of salt, I imagine enjoying hot salty chips at the beach or salty popcorn at the movies. Salt helps to enhance palatability, but is also far more than just a delicious condiment. Salt (in moderation) has many benefits and is a source of sodium, chloride and iodine.
Sodium and chloride are two of the seven essential macrominerals for mammals and while they are crucial for many body functions, excess salt in pet food can have negative effects in some of our patients. Sodium and chloride play vital roles in the regulation of acid-base balance, osmotic balance, transmission of nerve impulses and nutrient uptake.1
Comparing salt in pet food
When comparing salt in pet foods it is useful to know how to convert grams of salt into milligrams of sodium. Salt comprises one sodium and one chloride molecule, but their molecular weights are not the same. You can use the following equation to help:
“X” grams of salt ÷ 2.5 = grams of sodium x 1000 = milligrams of sodium
How much salt is too much?
There are many sources of salt in pet foods such as poultry, fish, meat and eggs along with added salt. Table 1 shows the recommended sodium levels for dogs and cats at maintenance. Some pet foods may contain more salt than animals need and the addition of treats and processed human foods to our furry friends’ diets can increase their salt intake even further. For example 85 g of processed ham contains 940 mg of sodium!1
To put this into perspective, a 5 kg cat being fed Hill’s Prescription Diet k/d dry would have a daily consumption of 162.5 mg of sodium.
Table 1. Recommended sodium levels in food for cats and dogs at maintenance1
| Young to middle aged cats | Older cats | Young to middle age dogs | Older dogs | |
| Sodium (% DM) | 0.2-0.6 | 0.2-0.5 | 0.2-0.4 | 0.15-0.35 |
Young, healthy pets with ready access to water may be able to cope with higher salt diets, excreting the excess in their urine. In older animals, especially those with underlying disease processes, high salt diets can be more problematic.
Salt in pet food and cardiovascular disease
When the cardiovascular system starts failing, its priority is to continue supplying oxygen and nutrients to the vital organs such as the brain, kidneys and heart. There are a number of compensatory responses in animals to aid this including the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS). Sympathetic stimulation, while increasing the heart rate and cardiac contraction, also causes sodium and water reabsorption increasing both preload and afterload. Activation of the RAAS system causes renin release and the formation of angiotensin II, which increases sodium and water retention further and stimulates aldosterone secretion.1
These compensatory mechanisms may result in dogs or cats with cardiac disease not being able to effectively excrete excess sodium like healthy animals can. A diet lower in sodium and chloride can be beneficial for dogs with heart disease, especially once there is dilatation of the heart and this becomes even more important once pets are in congestive heart failure.1 The Tufts Heartsmart website has some great tips about nutrition for pets with heart disease.
Salt in pet food and kidney disease
Animals with decreased renal function and reduced glomerular filtration rate (GFR) struggle to vary sodium excretion and thus cannot tolerate high or low dietary salt intake.1 Excess sodium has been shown to lead to the progression of chronic kidney disease (CKD) in cats. One study investigated 36 cats with varying renal insufficiency and compared the effects of high sodium (1.1% as fed) and low sodium (0.35% as fed) diets. The cats eating the high salt diet had an increase in serum creatinine, urea nitrogen and phosphorus in comparison to those eating the low salt diet.2
Salt and Lower Urinary Tract Disease (FLUTD)
While high salt in pet food diets can increase water intake and urine output and in the short term improve clinical signs of cats with lower urinary tract disease, there is a subset of cats that will be adversely affected by high salt levels.2,3 Hill’s Prescription Diet c/d Multicare is clinically tested to reduce the rate of recurrence of feline idiopathic cystitis signs by 89%4, without relying on high salt levels. Importantly, c/d Multicare is also suitable for multi-cat households and long term feeding.
Be mindful of the salt content of your patients’ diets by recommending foods suitable for their individual disease conditions. For example, patients with CKD can benefit from a diet such as Hill’s Prescription Diet k/d which has low sodium to help slow the progression of CKD.
For healthy pets we can feel confident recommending specific life stage diets such as Hill’s Science Diet 7+, 7+ Senior Vitality or Science Diet 11+ as these diets take into consideration the appropriate salt requirements for mature aged animals.
If you have a tricky case and would like some nutritional advice, our Hill’s veterinarians are available to help. Call our Veterinary Consultation Service on 1800 800 733.
If you would like to read more about nutritional management of cats with CKD check out Cats with CKD: Feeding Considerations.
Dr Sarah Robson BVSc(hons) MANZCVS(pharm) MVS MVSc GCCT
Dr Sarah Robson graduated with honours from the University of Melbourne in 2009 and went on to work in small animal practice. She then returned to U-Vet in 2012 to complete a clinical pharmacology residency and become a lecturer and general practice veterinarian in the busy teaching hospital. Sarah is a member of the Australian and New Zealand College of Veterinary Scientists in pharmacology and has completed a masters thesis investigating antibiotic resistance. Sarah joined Hill’s Pet Nutrition in 2021 as the Professional Consulting Veterinarian for Victoria and Tasmania.
References:
- Hand MS, Thatcher CD, Remillard RL, Roudebush P. Small Animal Clinical Nutrition 4th Edition Mark Morris Institute, Kansas 2010
- Kirk CA, Jewell DE, Lowry SR. Effects of sodium chloride on selected parameters in cats. Vet Therap 2006;7:333-346
- Forrester SD, Roudebush P. Evidence-based management of feline lower urinary tract disease. Vet Clin Small Anim 2007;37:533-558
- Kruger JM, Lulich JP, MacLeay J, et al. Comparison of foods with differing nutritional profiles for long-term management of acute nonobstructive idiopathic cystitis in cats. J Am Vet Med Assoc. 2015;247(5):508-517