It has long been known that vitamin D is important in human heart health. Research in people has found a strong relationship between congestive heart failure and vitamin D deficiency. In fact, vitamin D blood levels are useful predictors of survival in congestive heart failure patients. Heart disease leading to congestive heart failure is a common cause of illness and death in dogs, but little is known about whether vitamin D deficiency plays a role.
A recent study in the Journal of Veterinary Internal Medicine suggests that vitamin D may have a similar relationship in dogs with congestive heart failure.
About Vitamin D and its Effects on the Body
Muscle and nerve function are highly dependent on precise blood levels of calcium. Vitamin D plays an essential role in maintaining the correct blood calcium levels by regulating calcium absorption from the intestines. In humans, vitamin D has been found to directly aid heart muscle electrical activity and muscle contraction.
Humans can satisfy their vitamin D needs in two ways. It can be absorbed from food in the diet or from vitamin supplements. It can also be produced in the skin when exposed to adequate amounts of ultraviolet rays in sunlight. It is nicknamed the “sunshine vitamin.” Dogs cannot produce vitamin D in the skin and must rely on their diet for adequate intake.
The Vitamin D Study on Dogs
The researchers in the new dog study compared blood levels of vitamin D in dogs with congestive heart failure to normal dogs. They found similar results to those reported in human studies. Dogs with congestive heart failure (CHF) had lower blood levels of vitamin D. The researchers also observed that low blood levels of vitamin D were associated with poor survival. They were not able to show that actual blood levels could predict survival time as is possible in humans.
The study design failed to show diet was a cause of vitamin D deficiency in dogs with heart failure. The researchers relied on dietary questionnaires rather than direct analysis of diets. The questionnaire was not one that had been validated by research so its accuracy was limited. They also made various dietary assumptions to approximate vitamin D intake.
The study also failed to identify other potential causes for vitamin D deficiency. In humans, heart disease is associated the patient fitness and amount of body fat. Vitamin D is fat soluble and can be isolated in body fat and reduce blood levels. In this study, the dogs with CHF and the control dogs had normal amounts of body fat. No association with body fat was found.
Diuretics are standard for the treatment of heart disease in humans and dogs. These drugs reduce body and blood fluid levels by causing increased urination. Removing fluid helps reduce blood pressure and decrease the work load on the failing heart. Diuretics also increase the urinary loss of other chemicals in the blood. Theoretically, they could increase the elimination of vitamin D from the body and contribute to vitamin D deficiency in CHF dogs. The researchers did not analyze the urine vitamin D levels of dogs in this study, so it is unknown if medication contributes to the deficiency.
What Does the Vitamin D in Dogs Study Tell Us?
This is the first study to look at the relationship of vitamin D and CHF in dogs. More and better research is needed to fully explain vitamin D’s role in the disease. What is clear from the study is that dogs with CHF have reduced vitamin D blood levels. The study also shows that vitamin D deficiency in these patients decreases their survival times. Veterinarians need to consider vitamin D supplementation when treating CHF patients.
Dr. Ken Tudor
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