Antioxidants for Dogs: Can They Really Help?

Antioxidants are well known for their ability to mop up free radicals. These dangerous compounds are created as byproducts of normal metabolism. In the body, free radicals contribute to a process called cellular oxidation, which has been shown to damage cellular DNA, proteins, and other critical cell structures.  

Based on their ability to calm oxidative stress, antioxidants have been studied in humans as supportive therapies for a wide range of conditions. While this is compelling among humans, research among dogs is much more limited and the benefits of antioxidants are not as clearly defined.   

Some common antioxidants include:  

• Vitamin C  
• Vitamin E  
• Selenium 
• Beta-carotene  
• Polyphenols like curcumin  
• Alpha-lipoic acid 
• Coenzyme Q10  
• SAMe 

The most discussed dog studies involve antioxidant use in aging and cognition. In one study, older dogs fed food fortified with antioxidants such as alpha-lipoic acid and acetyl-L-carnitine learned tasks more quickly than older dogs on a control diet.  

Another study found that a diet enriched with antioxidants reduced age-related cognitive decline in dogs. A longer-term study found that adding antioxidants to their diet helped preserve learning ability in older Beagles.  

While this research is encouraging, not all studies have shown benefits. A study conducted in sled dogs found that antioxidant supplements didn’t reduce exercise-related oxidative muscle damage, and an exploratory study in hospitalized dogs showed no clear difference in clinical score or survival when antioxidants were given.  

While the research is less compelling, based on their biologic activity, antioxidant treatment may also be recommended for conditions including:  

• Inflammatory skin conditions like allergies, infections, and parasitic skin disease  
• Immune-compromised dogs 
• Liver disease  
• Kidney disease 
• Cancer  
• Inflammatory bowel disease 
• Eye diseases 

However, it’s important to understand there is limited direct evidence supporting antioxidant supplementation in these conditions. Instead, their recommendation is based on the general benefits of antioxidants and the fact that most dogs tolerate them well, so it’s more of a “better safe than sorry” situation or using them in very specific circumstances. 

Side effects of antioxidants depend on the ingredients included in the supplement in question. Vitamin E requires particular caution. One report showed that vitamin E caused severe clotting problems in dogs with warfarin-induced vitamin K deficiency. Vitamin E at higher doses is also linked to digestive upset.  

Antioxidant products including vitamin E may not be a good idea if your dog has a bleeding disorder or takes an anticoagulant medication. In this situation, ask your vet before giving an antioxidant supplement. 

Dietary balance is another potential issue. Because supplements provide additional nutrients that may already be found in your dog’s food, giving extra can cause an imbalance. In general, it’s best to check with your vet before putting your dog on a specific antioxidant or adding antioxidant-rich multivitamins to their diet. 

The best approach is to ensure your dog is eating a high-quality food instead of adding a supplement. A complete and balanced diet should be the main source of antioxidants, and a supplement should only be added if your veterinarian thinks it makes sense for your dog.  

If your vet recommends an antioxidant product, use it exactly as directed. Be sure to tell them about any other supplements, medications, or prescription diet your dog is on, or if they have a medical condition.  

Avoid giving your dog antioxidant supplements that have been formulated for people, which may contain doses that are far too strong as well as other ingredients that are not healthy for dogs. 

If your dog gets into a bottle of supplements or you accidentally give more than intended, call your veterinarian, an emergency hospital, or the Pet Poison Helpline (855-764-7661) right away. Because antioxidant products can vary so much, the risk depends on the exact ingredients, so have the package handy. 

If the product contains vitamin E and your dog has clotting problems or is on a blood thinner, treat an overdose as an emergency and seek veterinary help immediately. 

Do antioxidants help older dogs? 

Several studies of antioxidant-fortified foods found improvements in learning or age-related cognition in older dogs.  

Can I give my dog a human antioxidant supplement? 

It’s best to ask your veterinarian first. Human supplements may contain ingredients that are unsafe or even toxic to dogs.  

Are antioxidants a cure for disease? 

No. Some studies suggest possible benefits in specific settings, but the evidence is mixed and does not support using antioxidants as a treatment for diseases in dogs.  

What is the safest way to add antioxidants to my dog’s routine? 

The safest way to provide antioxidants is with a complete and balanced diet. If your veterinarian thinks a supplement can benefit your dog, follow their exact instructions for use.