Vitamin D and COVID-19 and Pet Nutrition

“During a WSAVA webinar on September 15 2020, speakers urged veterinarians to encourage owners to treat companion animals testing positive for SARS-Cov-2 with kindness and not to relinquish them. During his update on companion animal SARS-CoV-2, Dr Michael Lappin, Chair of the WSAVA’s One Health Committee, confirmed that the virus is a reverse zoonosis with infected humans passing it to companion animals in the very few animal cases that have been reported worldwide. Infected animals have displayed only mild symptoms and there is no evidence of transmission from a companion animal to a new human.” – Correspondence via email from World Small Animal Veterinary Association

Are you confused about our association of vitamin D, COVID-19 and pet nutrition? At Hemopet, we are not making or assuming such associations, but are bringing up research we find interesting in human and research medicine which clearly has a tangential in influence with regards to companion pets. Read on to find out…

COVID-19 and Vitamin D in Humans

Within the past couple of months, studies have suggested that people are more likely to test positive for and have clinical effects of SARS-CoV-2, the virus causing COVID-19, if they have a vitamin D deficiency. Studies have also suggested that the severity of disease symptoms is less in people who are sufficient in vitamin D. Additionally, more studies have suggested that treatment with vitamin D for COVID-19 improved patient outcomes.

The National Institutes of Health (NIH) has maintained since July 17, 2020, that, “There are insufficient data to recommend either for or against the use of vitamin D for the prevention or treatment of COVID-19.”

Overall, however, Hemopet believes that the evidence surrounding vitamin D – as a viable part of a COVID-19 therapy protocol or preventative measure – is promising and makes sense. Vitamin D does play an essential role in maintaining immune system regulation. Recently, adding selenium to the supplements taken is helpful too – the average human dose being 200-250 mcg daily and even more (double) for areas where soils are selenium-deficient such as Australia and New Zealand.

The vitamin D connection is especially important because approximately 40% of the U.S. population have vitamin D deficiency according to a study by the National Health and Nutrition Examination Survey (NHANES), which is a program run by the Centers for Disease Control and Prevention. Vegetarians are particularly vulnerable to this deficiency. As a result of vitamin D deficiency, you might have malformation of bones (rickets) in early life, bone density loss, fatigue, joint pain and muscle cramps. It makes sense as vitamin D regulates the body’s balance of calcium and phosphorus and promotes mineral absorption.

Studies have also suggested an association between vitamin D deficiency in relation to cancer, cardiovascular disease, diabetes, hyperparathyroidism, autoimmune diseases, malabsorption of fat, and even depression.

On top of that, the Northern Hemisphere is entering the winter months and the population will have less exposure to sunlight, the primary source of the cholecalciferol (vitamin D3) you need, although dogs and cats have a second related enzyme in their skin that metabolizes the 7-dehydrocholesterol before it can be converted to vitamin D3.

Now, this is not to suggest that you go out and purchase over-the-counter vitamin D supplements. We believe that the current conservative stance by the NIH is out of an abundance of caution due to the vitamin’s ready availability and the potential for overdosing.

Vitamin D is a fat-soluble vitamin – like vitamins A, E and K – that is stored in the liver, fat tissue and skeletal muscle. If taken in large doses, vitamin D toxicity can result. The complications with vitamin D toxicity include excess calcium in the blood (hypercalcemia), slowed mental and physical growth, bone pain, decreased appetite, nausea, vomiting, increased urination, excessive thirst, and kidney problems.

So, what do you do? We suggest scheduling an appointment with your medical doctor to have the vitamin D level tested in your blood. Once you and your doctor find out the results, we suggest discussing if adding a vitamin D supplement would be appropriate.

How does this relate to my companion pet?

Vitamin D is also an essential vitamin for companion cats and dogs. Vitamin D plays a similar role in the bodies of cats and dogs that it does in humans. Additionally, the health problems that can ensue with either a deficiency or toxicity in humans are the same in pets as well.

While vitamin D deficiency receives the spotlight in human medicine, the spotlight is split between deficiency and toxicity in the pet world due to the many types of pet food formulations.

For vitamin D deficiencies, homemade diets have been widely scrutinized and blamed.

Now, W. Jean Dodds and several other integrative veterinarians advocate for homemade diets because companion pet caregivers can control the ingredients in light of food sensitivities, provide the best and most optimum nutrition for their companion pet’s health needs, and can use the freshest ingredients possible.

On the flip side, we recognize the dangerous pitfalls associated with vitamin D deficiency and strongly urge pet caregivers to work with qualified animal nutritionists who can formulate diets that should contain a vitamin D supplement. If you do plan on switching to feeding homecooked meals to your pets, we encourage you to have their vitamin D blood levels checked prior to switching foods and a few months after the transition is complete.

However, those who focus on concerns of potential deficiency may end up ignoring the possibility of toxicities in commercial pet foods. Indeed, do a web search for “vitamin D deficiency in dogs”. One of the top search results will probably be an article by the Food and Drug Administration titled “Vitamin D Toxicity in Dogs” that discusses the massive dog food recall of late 2018 and early 2019 due to toxicity.

Hemopet has interviewed Steve Brown about how this toxicity occurred. Steve does not know exactly what happened in these recent cases of vitamin D excess, but he had several viable thoughts. Feel free to read our discussion with Steve by clicking here.


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Dodds, W. Jean. “A Hush-Hush Topic: Mislabeled, Undeclared, Unidentified or Missing Ingredients from Pet Foods.” W. Jean Dodds’ Pet Health Resource Blog, 14 Dec. 2015,

Dodds, W. Jean. “Nutrient Comparison of Popular Dog Food Ingredients.” W. Jean Dodds’ Pet Health Resource Blog, 31 Mar. 2018,

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Meltzer, David O., et al. “Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results.” JAMA Network Open, vol. 3, no. 9, 3 Sept. 2020, doi:10.1001/jamanetworkopen.2020.19722,

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