by Dr. Noélle Steyn and Dr. Heinri Spangenberg, Westside
All living organisms produce free radicals – unstable molecules that can cause damage to cells. Oxidative stress describes a state where the rate of free radical production within body tissues exceeds the ability of body systems to neutralize these free radicals. Free radicals are produced as part of normal physiological processes, but production of these free radicals increases during times of stress and high metabolic demand, such as fast growth, disease challenge, calving and peak lactation.
Normal cell respiration leads to the production of free radicals, of which superoxide radicals, hydroxyl radicals and hydrogen peroxide are the most familiar. These are also called reactive oxygen species. They play a role in immunity, cell differentiation, protein regulation and programmed cell death. Thus, radicals are necessary for optimal health, but an overproduction or accumulation of free radicals can lead to multiple diseases. Free radicals are reactive and unstable and can damage cell membranes, DNA, and proteins within the body, leading to impaired body functions, poor health, and reduced performance.
Free radicals are capable of existing independently and contain one or more unpaired electrons. Unpaired electrons make free radicals unstable as they tend to remove an electron – or donate their electron to another molecule or atom. This creates a chain reaction of electron donation or removal, resulting in more unstable and reactive molecules, with potential harmful effects to surrounding cells. This chain reaction can only be stopped by the body’s antioxidant systems.
Preventing oxidative stress
To prevent oxidative stress, free radicals must be neutralised. Firstly, the body makes use of various enzymes that can convert free radicals to harmless products like water and oxygen, glutathione peroxidase is an example of such an enzyme. Secondly, and what we will be focusing on, is antioxidants.
Antioxidants are molecules that can donate a hydrogen atom to a free radical, which then neutralises the free radical. Vitamin E, vitamin C, and glutathione (a selenium-containing enzyme) are probably the most familiar antioxidants. Using Vitamin E as an example, the molecule’s key feature is a hydroxyl group attached to a benzene ring. The electrons in the benzene ring are mobile, making it possible for the hydrogen in the hydroxyl group to be split off, to neutralise a free radical.
Limitations of Vit E
Vitamin E is an effective antioxidant that helps to delay aging and prevent disease. However, it has a relatively low bioavailability and is very expensive. The reported bioavailability of synthetic vitamin E is roughly 29% for swine and 15% for cattle. Being a fat-soluble vitamin, vitamin E absorption will depend on the absorption of fats from the diet. Low fat diets or poor fat digestion will decrease Vit E absorption. Lastly, studies have shown that the half-life of vitamin E decreases as the dosage increases. As a result, it becomes almost impossible to ensure a high enough level of antioxidants by using only vitamin E.
An alternative to Vitamin E
Using other antioxidants, like natural polyphenols, can deliver better results than Vitamin E alone. Polyphenols are plant compounds with high antioxidant potential and thus a beneficial solution to fight oxidative stress. However, they cannot replace the role of vitamin E in gene expression, neurological functions or as a regulator of enzyme activity. Therefore, polyphenols can only be used as partial replacement for vitamin E, to aid in the prevention of lipid oxidation and to act as antioxidants. By using a combination of antioxidants, these molecules act in synergy and boost antioxidant defences beyond the capabilities of vitamin E alone.
Some polyphenols have more hydroxy groups attached to their benzene rings per unit of weight than vitamin E, giving them a greater antioxidant potential. The reason for the higher antioxidative capacity of polyphenols compared to synthetic Vitamin E lies in the facts that polyphenols have more hydroxy groups than vitamin E (Figure 1), and that vitamin E has a long lipophilic tail with no antioxidant properties, further reducing its antioxidant capacity per unit, compared to selected polyphenols.
Solubility also affects antioxidant effectiveness. Fat-soluble vitamin E, for example, can only have an antioxidant effect at the level of the cell membrane, because cell membranes consist of phospholipids. Polyphenols can range from water-soluble to biphasic, meaning they are soluble in both water and fat, and as a result, they can have their effect throughout the entire cellular environment and not just at the cell membrane. Due to their high bioavailability and distribution characteristics, polyphenols provide support to the immune system, reproductive system, and antioxidant systems of developing embryos and offspring.
Polyphenols are carefully selected, taking into consideration the differences in water-solubility and fat-solubility, digestive physiology, radical affinity, and tissue distribution, to provide the antioxidant protection needed throughout the entire cell. This results in a multifaceted approach that offers broad protection against free radicals to improve animal health.
Read more about AOmix or contact Dr. Noélle Steyn for enquiries at noelle@westside.co.za
