Combating Oxidative Stress with Vitamin C

There are two types of vitamins: fat-soluble (A, D, E, and K) and water-soluble (B and C). Vitamin C is a water-soluble vitamin that acts as an antioxidant. Oxidation is a normal and necessary reaction in the body. Oxidative stress however, occurs when there is an imbalance between free radical production and antioxidant activity. When there are more free radicals present than can be kept in balance by antioxidants, the free radicals can start doing damage to fatty tissue, DNA, and proteins in the body, leading to a vast number of diseases over time. Antioxidants help to protect the body against free radicals. Free radicals are highly reactive; antioxidants help to stabilize these free radicals, making them less reactive. When there are not enough antioxidants to balance the free radicals in the body, oxidative stress can occur. Several factors affect levels of oxidative stress in dogs and cats including: 

  • Emotional stress
  • Age
  • Diet
  • Lifestyle
  • Exposure to chemicals and toxins
  • Amount of physical activity

Dogs and cats, unlike humans, can produce vitamin C and do not need supplementation under optimal conditions. However, many pets are often deficient in vitamin C due to common exposure to sources of oxidative stress.

What Is Vitamin C Used For?

Because of its antioxidant properties, supplemental vitamin C can be beneficial in cases of:

  • Cognitive decline
  • Immune system damage
  • Old age
  • Arthritis
  • Cancer
  • Allergies (acts as a natural antihistamine)
  • Infections (improves immune function by enhancing white blood cell function and activity) 
  • Excessive stress levels
  • Rigorous exercise/training
  • Acetaminophen toxicosis
  • Feline immunodeficiency virus
  • Chronic inflammation

Vitamin C maintains the health of collagen. It is helpful for dogs with arthritis, degenerative joint disease, hip dysplasia, and spinal disorders such as intervertebral disc disease.

Vitamin C is considered restorative when used in conjunction with other vitamins and minerals as it can protect tissue and collagen from degeneration. Holistic practitioners have also used vitamin C for viral applications such as feline leukemia, however, the data on its effectiveness for viruses is variable.

When to NOT use vitamin C?

Vitamin C is partially broken down into oxalate, then excreted through the urine, so any pet with a history of oxalate crystals or stones should not be supplemented with excess vitamin C. Also, avoid vitamin C supplementation in pets with copper storage disease of the liver. 

What to Look For in a Vitamin C Supplement:

Natural sources of vitamin C include many fruits and vegetables, including citrus, dark leafy greens, bell peppers, green beans, sweet potatoes, and zucchini. Vitamin C is a temperature-sensitive vitamin, so it can degrade easily when cooked. Any fruits and vegetables fed to your pet need to be processed (finely chopped or gently cooked) in order for them to be properly digested.

While I do include natural sources of vitamin C in many of my diets, I do like to use a high quality vitamin C supplement called BIO-C for some cases. I generally prefer vitamin C supplements that are mineral salts (calcium ascorbate or sodium ascorbate) because they have a neutral pH and are efficiently processed. BIO-C also includes lemon bioflavonoids which help to increase the utilization and absorption of vitamin C. 

Ascorbic acid supplements can be used for vitamin C, but it is important to keep in mind that they are acidic. The acidity of ascorbic acid can be beneficial in cases where the animal’s urine pH is too high (above 7.5) and/or has struvite crystals. If you do use an ascorbic acid supplement, I recommend keeping tabs on your pet’s urine pH using at home test strips to ensure it is staying between 6.5-7.5. For cats, palatability can be an issue, so a liquid option may be easier to administer.

How Should Vitamin C Be Administered?

Because vitamin C is water-soluble, any excess consumed orally will be eliminated through the urine, making it a reasonably safe supplement. For most applications, 500mg for every 20lbs of bodyweight twice daily is appropriate. Too much vitamin C taken orally can result in diarrhea, so start slow and monitor for any GI upset before working up to the full dose. 

For cancer cases, vitamin C can be administered in much higher doses intravenously. When used intravenously, plasma concentrations of vitamin C can be up to 25 times higher than when administered orally. IV Vitamin C therapy has been shown to be selectively toxic, killing early stage cancer cells without the excessive damage caused by traditional chemotherapies. Vitamin C also has synergistic effects when used in conjunction with chemotherapy. IV Vitamin C therapy has been used in other applications such as snake bites and sepsis, but these cases have not been well studied yet.

Key Takeaways

  • Vitamin C is an antioxidant that can help combat oxidative stress experienced by pets. 
  • Sodium ascorbate is my preferred vitamin C supplement, however, ascorbic acid can be used as long as urine pH is monitored. Ascorbic acid is poorly absorbed by dogs, often resulting in diarrhea. Ascorbic acid is very bitter; most pets will not eat the powder. Sodium ascorbate, on the other hand, is efficiently absorbed. This buffered form of vitamin C has fewer side effects such as diarrhea and reflux.
  • Start with a small amount and work your way up to 500mg per 20lbs body weight twice daily. Stop or decrease dose if diarrhea or other GI upset occurs.
  • IV Vitamin C Therapy can be used in severe cases of illness such as cancer, snake bites, and sepsis.
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