Vitamin C in Health and Disease: A Companion Animal Focus

Gordon, D. S., Rudinsky, A. J., Guillaumin, J., Parker, V. J., & Creighton, K. J. (2020). Vitamin C in Health and Disease: A Companion Animal Focus. Topics in Companion Animal Medicine, 39, 100432. https://doi.org/10.1016/j.tcam.2020.100432

Study Background

In 2020, Gordon and colleagues published a review article in Topics in Companion Animal Medicine titled Vitamin C in Health and Disease: A Companion Animal Focus. Unlike an experimental trial, this paper does not report new lab results. Instead, it compiles and evaluates findings from existing research on vitamin C in dogs, cats, and, where relevant, humans.

The review asks: What roles does vitamin C play in companion animals, and could supplementation help in disease?

Study Scope and Methods

• Type of study: Review article (synthesis of previously published research).
• Species covered: Dogs, cats, and, for comparison, humans.
• Focus areas: Vitamin C’s physiological functions, how levels change in illness, and the potential for supplementation in critical care settings.

Key Insights from the Review

Physiological Roles of Vitamin C

Vitamin C (ascorbic acid) is more than just an antioxidant—it is required for many normal body processes. The review explains how it:

• Builds and repairs tissues: Vitamin C is necessary for collagen synthesis, which supports cartilage, bone, skin, and blood vessels.
• Regulates the immune system: White blood cells store high amounts of vitamin C, which they use to fight infections, regulate inflammation, and kill bacteria.
• Protects against oxidative stress: Vitamin C donates electrons to neutralize free radicals and helps recycle vitamin E, reducing cellular damage.
• Supports hormone production: It acts as a cofactor in making catecholamines (like norepinephrine) and vasopressin, which regulate stress responses, circulation, and fluid balance.

Vitamin C in Illness

The review highlights that while healthy dogs and cats synthesize enough vitamin C in their livers, levels often fall during illness or trauma. Examples include:

• Sepsis and critical illness: Human patients with sepsis often have dangerously low vitamin C, linked to worse survival. In dogs, oxidative stress conditions like gastric dilatation-volvulus (bloat) also lower vitamin C levels.
• Liver disease and cancer: These conditions are associated with altered vitamin C status in both humans and companion animals.
• Parasitic infections: Dogs with leishmaniasis or sarcoptic mange were found to have significantly reduced plasma vitamin C, likely due to oxidative and inflammatory stress.

Therapeutic Potential of Vitamin C

One of the major questions the review raises is whether supplementing vitamin C could help critically ill animals:

• Human evidence: Small clinical studies show intravenous vitamin C may reduce inflammation, improve blood vessel function, and lower mortality in septic shock and severe burns.
• Veterinary evidence: While controlled studies are scarce, early data in dogs and cats suggest vitamin C might lessen oxidative damage during sepsis, ischemia-reperfusion injury, or cancer. For example, high-dose vitamin C slowed melanoma cell growth in vitro, and supplementation buffered oxidative stress in transplant and trauma models.

Practical Considerations

• Accessibility: Vitamin C is inexpensive and widely available, making it attractive as a supportive therapy.
• Safety: The review notes that supplementation is generally safe, but very high doses can increase oxalate levels, raising concerns about kidney stone risk—particularly in animals already prone to urinary issues.
• Current stance: Until more veterinary trials are conducted, supplementation should be considered experimental, not standard of care.

Relevance to Dogs

The review emphasizes that dogs do not typically need dietary vitamin C because they produce it internally. However, during illness, trauma, or oxidative stress, their natural synthesis may not be enough. This makes vitamin C supplementation a promising avenue for supporting canine patients in intensive care or with chronic inflammatory disease, though much more controlled research is needed.

Limitations & Future Directions

• Few controlled veterinary trials exist on vitamin C supplementation.
• Optimal dosing and delivery methods (oral vs. intravenous) remain unclear.
• More clinical studies are needed before vitamin C can be recommended as standard veterinary care.