Concerns regarding sodium intake and its impact on human health have been discussed and investigated for decades. Similarly, there have been efforts to better understand the effects of dietary sodium on feline health – specifically those at risk of hypertension or chronic kidney disease.
Back in 2018, the Winn Feline Foundation published a review article that evaluated the body of evidence (at the time) regarding the risks, safety, and benefits of various sodium levels in feline diets. At the time, the recommended safe upper limit (SUL) for sodium intake in cats was determined to be 740 mg/mJ (megajoule) of metabolizable energy (ME), or 1.25 g/kg in 4000 kcal ME/kg diets.1 Safe upper limit implies the maximum concentration or amount of a nutrient - in animal feed - that is not associated with adverse effects. This is determined by the National Research Council. Most of the studies leading to that recommendation involved healthy cats, and no correlation was shown between high dietary sodium and adverse impacts on renal function and health. Other studies in cats have evaluated cardiac function and anatomical parameters; these were cats without evidence of heart disease who were fed different amounts of dietary sodium. No changes in cardiac anatomy or function were identified in those cats – even those fed high levels of dietary sodium over a period of months. Studies of the effects of increased dietary sodium intake on blood pressure in cats have similarly demonstrated no association - regardless of health status (e.g. healthy young adults, healthy aged animals, or cats with impaired renal function), diets higher in sodium did not significantly impact blood pressure measurements. However, studies evaluating the long term effects of feeding high-salt diets on feline health were lacking until more recently.
In humans, chronic high dietary sodium intake has been associated with the development of hypertension and hypertension-related cardiovascular diseases, renal diseases, gastric mucosal damage, and even gastric neoplasia. Heart disease - particularly hypertrophic cardiomyopathy - is relatively common in cats, and affects up to 20% of the feline population. Hypertension is another common problem in cats; most feline hypertension develops secondary to chronic kidney disease or hyperthyroidism (only about 20% of cases are considered idiopathic). Chronic kidney disease and hypertension are more prevalent in older cats.
Low-sodium diets have historically been recommended for hypertensive cats based on older data stemming from studies in laboratory animals and humans. The 2018 American College of Veterinary Internal Medicine consensus guidelines regarding systemic hypertension in dogs and cats state that dietary salt restriction for managing hypertension is controversial but that high dietary sodium intake should be avoided.2
There is strong evidence showing that lowering sodium intake significantly reduces blood pressure in people – whether they have normal or high blood pressure. In a prospective, crossover study of 213 people, a low-sodium diet significantly lowered systolic blood pressure in approximately 75% of individuals compared to those who received a high-sodium diet. The authors further demonstrated that the blood pressure-lowering effect of dietary sodium reduction was comparable to the effects of first-line antihypertensive medications.3
More recently, findings of a long term (5 year) prospective, randomized controlled trial of healthy, aged cats (~11.5 yrs old) were published.4 These cats were fed a control diet or a high-salt dry diet for up to 60 months. Annual monitoring of these patients included bloodwork, kidney function parameters, blood pressure, as well as kidney and cardiac imaging. Diet had no significant effect on any of those variables over time – there were no significant differences between controls and the cats fed a high-salt diet. The authors concluded that in healthy, aged cats, feeding a diet containing 3.26 ± 0.30 g/Mcal ME sodium was safe (for up to 5 years – the interval of time of that study). Although the sodium content in feline diets can vary, that amount of sodium (3.26 ± 0.30 g/Mcal ME) is nearly 3 times higher than what is found in standard feline diets.
In summary, the most current evidence demonstrates that chronic high dietary sodium intake is safe in healthy aging cats and that ill-effects on kidney and heart function and blood pressure are not expected. There remains insufficient data to support specific recommendations regarding sodium restriction for feline patients with cardiac or renal disease. Future studies are still warranted.
References:
[1] Sodium in feline nutrition. J Anim Physiol Anim Nutr 2017;101:403-420. doi: 10.1111/jpn.12548
[2] ACVIM consensus statement: Guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats. J Vet Intern Med. 2018; 32: 1803–1822. doi: 10.1111%2Fjvim.15331
[3] Effect of Dietary Sodium on Blood Pressure: A Crossover Trial. JAMA. 2023;330(23):2258–2266. doi:10.1001/jama.2023.23651
[4] Long-term safety of dietary salt: A 5-year ProspEctive rAndomized bliNded and controlled stUdy in healThy aged cats (PEANUT study). J Vet Intern Med. 2024; 38(1): 285-299. doi:10.1111/jvim.16952
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