Sodium - Na

Sodium is the main extracellular electrolyte, working closely with potassium (the sodium-potassium pump). It is responsible for the body's water balance (regulating osmotic pressure), blood pressure, and proper nerve conduction and muscle contraction [1]. The NRC requirement for an adult dog is MR 75 mg, RA 200 mg / 1000 kcal ME; in the cat it is lower — MR 160 mg / 1000 kcal ME (RA about 170 mg), reflecting the different physiology of the cat's kidneys [1].

Where it's found: Store-bought muscle meat is bled out and poor in sodium — this is a common reason for low sodium in homemade diets. The richest reservoir is fresh or dried blood (plasma, dried hemoglobin). Sodium is supplemented with an addition of dried hemoglobin or non-iodized rock/sea salt in microdoses (1 g of table salt = about 390–400 mg of sodium) [1]. Do not pour out the juice from thawing meat — it contains soluble sodium.

Deficiency: Resulting from a meat diet alone is rare, but with bled-out store meat it is easier to make than it seems. Clinical deficiencies are almost always a secondary problem — sudden fluid loss (vomiting, diarrhea, extensive burns) or Addison's disease (adrenal cortex insufficiency destroying the sodium-retention mechanism) [2].

Excess: Dogs and cats have a lower tolerance for excess salt than humans, and cats are more sensitive than dogs [1]. Salt poisoning is directly life-threatening — it most often occurs when the animal eats salty table scraps (cold cuts, chips) or homemade salt dough. Excess salt rapidly draws water out of cells (including the brain), so after extreme thirst, vomiting and diarrhea, neurological symptoms quickly appear: disorientation, muscle tremors, convulsions, and ultimately death. A raw diet contains a lot of moisture (about 65–75%), which gives the kidneys a buffer to excrete the excess — but that is no reason to add salt.

What to watch for

Always consider sodium together with potassium — more on their mutual proportion in the article Sodium : potassium ratio. Sodium is not a tool for managing a cat's urinary tract health — do not add salt "to dilute the urine," because overall hydration is what matters [1]. In the cat, do not use iodized salt to supplement sodium — cats are sensitive to excess iodine, which should come from a controlled source (algae, a dedicated supplement), not from salt.

Sources

1. National Research Council (2006). Nutrient Requirements of Dogs and Cats. National Academies Press. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
2. Hand MS, Thatcher CD, Remillard RL, Roudebush P, Novotny BJ (2010). Small Animal Clinical Nutrition, 5th Edition. https://www.markmorrisinstitute.org/sacn5.html