Professor Jo-Anne Murray
PhD, MSc, PgDip, BSc (Hons), BHSII, RNutr, PFHEA University of Glasgow Veterinary School

What are antioxidants?

Antioxidants are often talked about as being good for us and our horses, but what are they and why are they beneficial? Antioxidants are substances that can help protect the cells in the body from free radical damage. Antioxidant substances include the vitamins E, C and A, which are effective free radical scavengers. The minerals selenium, copper, zinc and manganese produce antioxidant enzymes in the body. Other antioxidants include lipoic acid, coenzyme Q10, isoflavins and turmeric.


What are free radicals?

Free radicals are molecules that the body produces as a result of oxidation. Oxidation is a normal process that takes place in the body. When a substance in the body oxidises; for example, in the case of energy production where the body transforms nutrients such as carbohydrates, fats and protein into energy, then free electrons (also known as free radicals) are released. The production of these free radicals is an unavoidable consequence of oxidation.


Free radicals like to be in pairs so they scavenge the body to find other free radicals that they can pair with; hence, these free radicals (also known as unpaired electrons) search for electrons from other molecules in the body, which can then cause damage to the other molecule. The other molecule that has had its electron stolen then also becomes oxidised and the free radicals from this other molecule will then look to steal an electron from another molecule and so a vicious chain reaction of stealing electrons begins. When this cycle becomes more than the body can combat, this is referred to as oxidative stress, which may lead to cell damage (ageing and disease) or destruction.


How can antioxidants combat free radicals?

Antioxidants act to stabilise free radicals and stop the destructive process that can lead to oxidative stress. These antioxidant substances scavenge free radicals, they do this by giving electrons to the free radicals and this neutralises them. Even in a healthy horse maintained at pasture, some free radical production will occur as part of normal body processes; however, antioxidants can easily combat these.


Vitamin E has been referred to as the antioxidant hero as it makes a large contribution to the horse’s natural antioxidant defences. Vitamin E is a fat-soluble compound and it has been reported that if a horse receives adequate amounts of vitamin E in its diet, muscle membranes are more likely to remain intact during exercise, with less cell breakdown and less likelihood of muscle enzymes entering the bloodstream. Selenium works alongside vitamin E as part of the body’s antioxidant defence system. Selenium is an important part of an enzyme called


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