Polyphenols are plant-based nutrients that evolved as a natural defense against plant pathogens and protection from ultraviolet radiation. They are the most abundant antioxidants in our diet, and evidence for their role in the prevention of degenerative disease in the human population is strong. Polyphenols represent an immense variety of compounds and are divided into four main categories: flavonoids, phenolic acids, stilbenes, and lignans. The two most prominent are the flavonoids and the phenolic acids. The flavonoids, alone, represent over 4,000 different compounds that occur ubiquitously in the plant kingdom.
Flavonoids are known as nature’s biological response modifiers because of their ability to alter the body’s reactions to allergens, viruses, and carcinogens, and to protect cellular tissues against oxidative attack. A group of highly coloured pigments found in the edible pulp of many fruits and vegetables, flavonoids impart a bitter taste when isolated. Citrus fruits, such as oranges, lemons, limes, grapefruit, and kiwi, are particularly rich sources of flavonoids.
Phenolic acids and their derivatives are powerful free radical antagonists. Despite their low bioavailability, they demonstrate potent anti-inflammatory, antiviral, antibacterial, antiallergic, antihaemorrhagic, and immune-enhancing properties. The most intensely studied of the phenolic acid compounds include those isolated from turmeric, a perennial herb of the ginger family and a major ingredient in curry; green tea, a rich source of compounds called catechins; and extracts from the fruit of the olive tree.
Unlike vitamins, polyphenols are not required for growth and development. Nevertheless, there is strong clinical evidence showing their role in reduction of the risk of chronic disease. Initially considered simple antioxidants, the actions of polyphenols and their metabolites are now understood to occur through indirect antioxidant protection. Even at exquisitely low concentrations in the cell, polyphenols can activate endogenous (internal) antioxidant defense systems, modify cellular signalling processes, and inhibit the activities of oxidative and inflammatory molecules.
We know that most, but not all, polyphenols are active in cell signalling pathways that involve activation of nuclear factor erythroid 2-related factor 2 (Nrf2). This transcription factor (DNA signalling molecule) normally lies dormant in the cytoplasm of the cell. Once activated, Nrf2 will travel to the nucleus of the cell, where it orchestrates the activities of a wide array of genes involved in the manufacture of the cell’s antioxidant enzymes. By controlling the activities of Nrf2, polyphenols can effectively regulate the cell’s entire arsenal of antioxidant defenses.
Polyphenols are also involved in the suppression of nuclear factor-kappaB (NF-kB), a protein complex that controls transcription of DNA, cytokine production, and cell survival. NF-kB plays a key role in regulating the body’s immune response to infection. The vast majority of serious diseases are rooted in uncontrolled chronic inflammation resulting from dysregulation of the body’s immune response mechanism. So, by being able to turn down the actions of NF-kB, the body’s inflammation thermostat, polyphenols play an important role in long-term health.
Through their ability to modulate gene expression controlling both cellular redox balance (Nrf2) and inflammation (NF-kB), polyphenols play an essential role in reaching one’s genetically determined lifespan. Hence, they are indispensable to longevity and good health—indeed, they are Lifespan Essentials.
Arriving at a recommended daily intake for individual polyphenols is not possible due to the thousands of flavonoids and phenolic acids regularly consumed by a given population on a daily basis. However, epidemiological (population-based) evidence confirms that these nutrients exert powerful synergistic effects at normal levels of dietary intake. Anyone consuming a healthy diet with the prescribed five-to-seven servings per day of fruits and vegetables would be consuming a wide range of these plant-based nutrients. Consequently, it is reasonable to select a diet known to be plentiful in polyphenols and to use it as a basis for estimating the optimal daily intake of flavonoids and phenolic acids. These values can, in turn, be employed to represent the recommended intakes for these nutrient categories in our Blended Standard model.
The two healthiest diets in the world are the traditional Mediterranean diet, found in the Italy/Greece/Crete regions, and the Okinawan diet of Japan. Consequently, for this edition of the guide, NutriSearch has selected a very recent population-based study conducted in the Molise region of Italy, which lies in the heart of the Mediterranean. The Molise study (2016) is the first to report a median intake of flavonoids using the most recent harmonized data from the Eurofir BioActive Substances database and the US Department of Agriculture food composition tables.
The recommended daily intake for the flavonoids in our Blended Standard is based on the median flavonoid intake of 269 mg per day found in the Molise study.1 The phenolic acid intake of 134.5 mg per day in our Blended Standard is based on an estimated 2:1 dietary ratio of flavonoids to phenolic acids (flavonoid intake based on the Molise study) as previously reported by Scalbert and Williamson (2000).2 The calculated daily total polyphenol intake of 403.5 mg, based on the Molise study, is in general agreement with previous US-based studies that estimate a total phenolic intake of 336 mg for individuals consuming up to 10 servings of fruits and vegetables per day.3;4
NutriSearch Corporation is a Canadian company specializing in nutrition and health research, focussed primarily on multiple vitamin and mineral supplementation.
Our main product is the NutriSearch Comparative Guide to Nutritional Supplements™, which examines current research on the health benefits of supplementation for prevention of degenerative disease. The guide also includes comparisons of broad-spectrum supplements available in various markets around the world, is available in various regions. The guide for the Americas includes product comparisons from Canada, Colombia, México, and the United States. We also publish a guide for Australia and New Zealand.
NutriSearch is also available as a consultant to nutritional supplement manufacturers wanting to improve their supplements.