Balancing Calcium and Phosphorus for Dogs

Dr. Dodds and Hemopet advocate for the advantages of properly-balanced and prepared homemade meals for companion pets. Indeed, these include the fact that companion pet parents can control and choose ingredients, customize for age and health, and modify according to any food sensitivities and intolerances.

Yet, we understand why some veterinary professionals are concerned about homemade diets for their pet companion. And, yes, we agree with their concerns. That is why we encourage companion pet parents to work with reputable and experienced veterinary/animal nutritionists.

With that being said…what is their concern? For many, it can be the very complex mineral assessment that veterinary nutritionists need to consider for our pets, namely: The Calcium:Phosphorus Ratio.

The essential minerals of calcium and phosphorus need to be delicately and accurately balanced relative to each other. Both calcium and phosphorus are provided through foods, but an excess or a deficiency of one or the other can lead to deleterious effects on the body and health.

Vitamins D2 and its active form, D3, compound this issue of mineral balance. Their role is to enable proper absorption and uptake of calcium and phosphorus, as well as assist with other calcium and phosphorus functions in the body.

Compounding the issue even further is how the two vitamin Ds are given. Vitamin D3 (calcitriol) is not nutritionally accessible and must be added as a supplement. It is available only through sunlight, which is often insufficient these days with depletion of the ozone layer and pollution, and by supplementation. Vitamin D2 (calcidiol) needs can be achieved through dietary means.

Further, the function of vitamin D is complicated by the nature of its absorptive aid properties. Vitamin D aids the intestinal absorption of calcium, and helps ionized phosphorus (i.e. phosphate) be reabsorbed back into the bloodstream from the small intestine and kidneys.

The parathyroid gland and fibroblast growth factor 23 (FGF-23) also play important roles.

Indeed, the interactions of calcium, phosphorus and vitamin D can result in a variety of metabolic, biochemical and physiological outcomes.

Yes; it surely is confusing and complicated.

The optimal dietary calcium to phosphorus ratio in dogs should be 1.2:1 to 1.3:1. The ratio appears small, but it is significant. So, we thought we would give you two easily digestible conditions (pun intended) that illustrate the effects an imbalance of calcium and phosphorus can cause.

Calcium Excess

An easy example of excessive calcium intake is rickets-like signs in puppies or young dogs. Puppies will experience:

  • Bone deformation or bowed limbs
  • Bone pain and swelling
  • Fractures
  • Stiff gait or limp

Typically, we see rickets-like conditions with dogs fed only all-meat diets.

The remedy? Rickets-like symptoms in dogs can be reversible if caught early enough. Basically, a companion pet parent needs to balance the calcium to the phosphorus intake and add a vitamin D supplement.

Excess Phosphorus

Nutritional secondary hyperparathyroidism is an excess of phosphorus compared to calcium in the diet. When phosphate levels are maintained at untenable levels in the blood or are unmatched by sufficient calcium intake, calcium in the blood drops causing hypocalcemia. Low serum calcium, in turn, signals the parathyroid to call upon the calcium in bones to replenish what is missing in the blood. The demineralization of bones cause weakness, possible fractures and neurological dysfunction.

Again, the cause can be attributable to dogs fed only all-meat diets.

The Takeaway

Bear in mind that the two examples provided here are simple. There could be more complex and underlying conditions causing excessive or insufficient levels of calcium or phosphorus. These examples demonstrate the importance of dietary balances (particularly of minerals like calcium and phosphorus), and how easily dietary imbalances can result in health conditions.


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