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Cancer and Polyphenols

Monday October 10th 2016


Other than the obvious nutritional benefits of the added fibre and essential vitamins and minerals, it is the polyphenols, (which are a subgroup of phytonutrients of plants) that have really caught researchers and food manufacturers attention in recent years. There are over 8000 different polyphenols that have been identified and it is their antioxidant properties that are believed to assist in the prevention and treatment of diseases associated with oxidative stress such as cancer and cardiovascular disease. 


Antioxidants basically work like mops in our body and help to neutralise free radicals, thereby protecting cells from free radical damage. When there is not enough protection from free radicals, normal cell function is compromised, which can lead to tissue degradation and increase the risks of developing chronic diseases like cancer, Alzheimer’s disease, cardiovascular disease and so on (Scalbert et. al, 2005).


As secondary metabolites of plants, polyphenols are generally involved in defence against ultraviolet radiation or deterrence of pathogens and may contribute to the bitterness, astringency, colour, flavour or oxidative stability of a plant. Of particular interest are a group of phytochemicals called phytoalexins that protect plants against insects, fungal attacks and UV damage (Tan et al, 2007). These particular compounds also support the destruction and elimination of damaged cells, before they have time to accumulate and make us sick.


Usually normal healthy cells stop dividing at the end of a natural life cycle and die, whereas those that are exposed to excessive free radical damage can start to replicate at abnormal rates, leading to abnormal cell growth that defies this natural cell cycle. Research indicates that these bitter phenolic compounds are used in natural cell cycle regulation through their ability to achieve apoptosis or cell death of abnormal cells (both cancer and pre cancer cells) whilst having no impact on normal healthy cells. This is believed to be due to their affinity for cells that contain a specific enzyme called CYP1B1 found only inside abnormal cells. When phytoalexins enter a cell containing CYP1B1, a process of molecular activation of the occurs, which ultimately results in the abnormal cell ceasing to grow or die. Therefore, this relationship between these bitter compounds and CYP1B1 results in a highly targeted, dietary rescue mechanism for killing cancer cells (Potter and Burke, 2006). This fascinating understanding may be the basis for our evolutionary defence against cancer development.


Phytoalexins are found in abundance in the outer layers and skins of fruit and vegetables and are what gives fresh produce their bitter taste. Unfortunately due to a range of factors including modern farming methods, pesticide spraying, genetic modification, food processing and preparation as well as environmental conditions, it is estimated that despite our efforts to eat plenty of fresh fruit and vegetables, we are consuming very little of these bitter compounds compared to that would have occurred in our diet 100 years ago (Tan et al, 2007).


Explanations for why our diets have become so deficient in these health promoting natural bitter polyphenols include:


  • Modern Farming Methods: As these bitter compounds are our plants natural pesticides, commercial farming methods including pesticide spraying has led to a gradual decrease in the levels of these natural pesticide fighting compounds in our fruit and vegetables. This is why organic produce is far superior in nutritional quality than regular fruit and vegetables in our food supply.


  • Modern Crop Varieties: Human preferences has resulted in the selection of sweeter tasting plants over time that produce fewer of these bitter compounds over the more traditional bitter varieties that would be far richer in these natural compounds.


  • Harvesting: Crops are usually harvested before they have had time to ripen on the plant, effectively reducing their nutritional value, including the levels of these bitter compounds. Transportation and cold storage of produce negatively affects polyphenol levels in fruit and vegetables.


  • Food Processing and Preparation: Often the skin, pith and roots are discarded in modern day food preparation, which often contain the highest levels of these polyphenols. In addition to this, many of these compounds are water-soluble and leach out during cooking processes.


  • Insufficient intake: Most Australians simply do not eat enough fruit and vegetables. In fact, recent health survey statistics have shown that less than 6% of Australians consume sufficient serves of fruit and vegetables on a daily basis (AIHW, 2012).


Evidently, it is now very difficult in today’s society to consume enough of these life-saving bitter compounds through diet alone. This has led to comprehensive research in the area and the development of a range of supplements that are essentially concentrated versions of these compounds to help supplement our nutrient poor diets. 


For more information on polyphenols and how to improve your overall health and nutrition please speak to your NEMQ health professional.





  • Scalbert, C. Manach, C. Morand, C. Remesy, L. Jimenez. 2005. Dietary Polyphenols and the prevention of diseases. Critical Review Food Science & Nutrition 45(4):287-306. DOI: 1080/1040869059096





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