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Interview: Comparing the Antioxidant Functions of Vitamin E and Polyphenols

19 November 2013 - With economic downturn in some geographies and high grains and oilseeds prices, the feed industry remains challenged and continues to seek solutions to reduce costs. However, lowering costs by reducing or deleting some additives from the diet or looking for cheaper solutions, could be compromising on quality and performance.



DSM warns that the replacement of essential micronutrients with other products might not be the right way forward.

Dr. Gilberto Litta, Global Category Manager Vitamins Marketing - Animal Nutrition and Health at DSM, shared his views with Feedinfo News Service regarding the claimed opportunity of replacing part of Vitamin E with polyphenols.

[Feedinfo News Service] Why is Vitamin E an essential nutrient in animal nutrition?

[Gilberto Litta] Vitamin E (alpha-tocopherol) cannot be synthesized by the animals and is therefore a dietary essential micronutrient, required by all animals and man for a multitude of metabolic processes. Vitamin E is primarily known as nature’s most powerful lipid-soluble chain-breaking antioxidant, but its physiological importance is much broader. Vitamin E is required for normal growth and reproduction. It helps maintain the structural integrity of all tissues, supports the development of the nervous system and substantially contributes to optimum health and disease resistance of farm animals due to its modulating effects on the immune system.

[Feedinfo News Service] Could you elaborate more about the antioxidant function of Vitamin E?

[Gilberto Litta] Life for most living organisms on earth without oxygen is impossible, but the high oxygen concentration in the atmosphere is potentially toxic for living organisms. Therefore it’s part of the evolution that living organisms develop specific antioxidant protective mechanisms to deal and survive in an oxygen-rich environment. The “antioxidant system” works basically on three levels: prevention of free radical formation, chain-breaking antioxidants inhibiting peroxidation and systems that eliminate damaged molecules or repair them. All antioxidants in the body function work in concert to provide antioxidant defense and their respective roles are well defined. Looking at vitamin E and polyphenols as example, these two groups of biologically active compounds are quite different in their efficacy, mode of action and research status. Vitamin E simply can’t be replaced by polyphenols based on current scientific knowledge.

[Feedinfo News Service] What are polyphenols?

[Gilberto Litta] Polyphenols are an extensive group of chemicals found in plants, normally as glycosides (conjugated with glucose and other carbohydrates). More than 8000 such compounds have been isolated and described. Numerous studies have demonstrated the beneficial effects of polyphenol-rich foods, including anti-cancer, anti-inflammatory, and cardiovascular protective effects, but positive associations between polyphenols intake and animal health are not always the case. The association between intake of polyphenols and impact on animal health remains unclear. First we still do not know enough about the processes of polyphenol absorption and their metabolism in the body, their availability and metabolism by gut microbiota. Most polyphenols are poorly absorbed in the gut and their concentration in the target tissues is comparatively low. Secondly, more research should be conducted to understand molecular mechanisms of polyphenol action in the biological system.


[Feedinfo News Service] What is the relationship between polyphenols and the antioxidant function?

[Gilberto Litta]
The fact is that working with in vitro systems like ORAC, many polyphenols display an excellent antioxidant activity, but these findings are not confirmed in vivo. As said the main reason is most probably due to the very low efficacy of absorption and concentration in target tissues is very low. Additionally polyphenols are normally added in vivo as plant extracts like grape extract most of the cases in glycoside form: metabolic modifications occurring in vivo may substantially influence the antioxidant activity of dietary polyphenols. Finally, polyphenols are typical xenobiotics for animals and humans, metabolized as such and rapidly removed from the circulation. Therefore there is now in the scientific community quite a consensus in saying that in vitro data cannot simply be translated into the in vivo situation.

To further stress this matter, it is important to measure the contribution provided by a compound to the antioxidant system. According to Halliwell (Halliwell et al., 2005) given a total antioxidant value in plasma of over 103 mmol/l, a minimum concentration of 20–50 mmol/l additional antioxidant from dietary sources would be required to make a significant contribution to systemic antioxidant capacity. High intakes of dietary polyphenols, however, typically result in unconjugated serum levels of up to 1 mmol/l. Therefore it seems likely that antioxidant activity is not a major benefit of polyphenols.

[Feedinfo News Service] Why do some authors conclude that the feeding of polyphenols as grape extracts to both humans and farmed animal result in antioxidant effects?

[Gilberto Litta] Polyphenols might show such effects in the gastrointestinal tract, where they may come into direct contact with cells, without having been absorbed and metabolized. Some authors reported that polyphenol activities could be associated with enzyme inhibition and proliferative activity. Finally we can measure an increased antioxidant capacity in blood after the consumption of polyphenols and this can be explained by the fact that what we measure is not caused directly by the polyphenols, but most likely results from increased ascorbate and urates levels derived from metabolism of polyphenols and increases in urates concentration, which is not necessarily beneficial.

[Feedinfo News Service] In conclusion, what is your opinion with regard to the proposed partial replacement of Vitamin E with plant extracts containing polyphenols?

[Gilberto Litta] The first aspect to closely evaluate is the physiological and biochemical functions played by these compounds. The comparison shows that while for Vitamin E aspects like composition, absorption, metabolic transformation within tissues and delivery to target tissues are fully and clearly described and documented the same can’t be said about polyphenols. Hence these two groups of biologically active compounds are quite different in their efficacy and mode of action. Although some data indicate positive effects of grape extracts on meat quality, these are not comprehensive enough to justify such a replacement, since meat quality is only one of many important Vitamin Е-related issues in animal production. Polyphenols can be part of the above mentioned antioxidant system, but in the light of current knowledge we can conclude that polyphenols cannot replace Vitamin E in its main biological functions.


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Published: 19/11/2013