- Nirusha Pahladi ANutr
Polyphenols are organic compounds found abundantly in plants; they have become an emerging field of interest in nutrition in recent years. Polyphenols comprise flavonoids, phenolic acids, tannins, lignans and coumarins; they are naturally occurring compounds found largely in fruits, vegetables, cereals and beverages. Fruits like grapes, apple, pear, cherries, nuts, olives and berries contains up to 200–300 mg polyphenols per 100 grams fresh weight. Typically a glass of red wine or a cup of tea or coffee contains about 100 mg polyphenols; Cereals, dry legumes and dark chocolate also contribute to the polyphenolic intake. Polyphenols have been linked to various health benefits. A growing body of research indicates that polyphenol consumption may play a vital role in health through the regulation of metabolism, weight, chronic diseases and cell proliferation.
Phenolic compounds are a diverse, bioactive, and pervasive category of plant secondary metabolites that comprise an essential part of the human diet and are of considerable interest due to their biological properties. The regular consumption of polyphenol-rich foods provide significant protection against the development and progression of some chronic diseases such as obesity and diabetes, cardiovascular diseases and colon cancer.
Picture adapted from Pandey and Rizvi (2009)
Phenolic compounds are beneficial nutrients that protect human health by fighting against the free radicals produced in the body cells and preventing oxidative damage. Evidence suggests that phenolic compounds can modulate/regulate or inhibit many cell signaling pathways in the human body. Flavonoids, in particular are useful in the prevention of inflammatory signaling pathways (e.g. the arachidonic acid pathway).
Phenolic compounds have been found to inhibit inflammatory enzymes such as phospholipase A2, Cyclooxygenase 1/2 and Lipoxygenase. These compounds are mainly able to decrease cell proliferation, angiogenesis, and leukocyte immobilization and reduce 5-lipoxygenase enzyme activities. Tea polyphenols are able to regulate/modulate COX-2 enzyme activity and gene expression in different types of cancer cell.
Foods rich in polyphenols.
Though tea, dark chocolate, red wine, and berries are likely the best-known sources of polyphenols, many other foods also contain high amounts of these beneficial compounds. Polyphenols are largely founds in:
Fruits (apples, apricots, avocado, berries, cherries, grapes, peaches, pears, pomegranate, citrus fruits, plums, tomatoes)
Legumes (black & white beans, tempeh, tofu, soybean sprouts, soy milk)
Vegetables (artichokes, asparagus, broccoli, carrots, potatoes, onions & spinach)
Herbs and Spices
Cereals (oats and wheats)
Nuts & seeds
Beverages (teas, coffee, chocolate, red wines, vinegars, olive and rapeseed oil).
Number of studies has demonstrated that consumption of polyphenols reduces the incidence of coronary heart diseases. Polyphenols are potent inhibitors of LDL oxidation and this type of oxidation is considered to be a key mechanism in development of atherosclerosis.
Polyphenols may also reduce your risk of developing a blood clot. Blood clots are formed when platelets circulating in your bloodstream begin to clump together. This process is known as platelet aggregation and is useful in preventing excess bleeding. Excess platelet aggregation can cause blood clots, which can have negative health effects, including deep vein thrombosis and stroke.
Polyphenols have strong antioxidant and anti-inflammatory effects; Phenolic compounds may prevent systemic and/or localized inflammation by restoring the redox balance to reduce oxidative stress, and by modulating inflammatory responses through mitigation of cytokine pathways.
Flavanoids such as anthocyanins, catechins, flavanols, flavones, flavanones, and isoflavones, may neutralize free radicals and decrease cancer risk by arresting cellular growth in tumor. Specific types of cancers with evidence of beneficial effects from a polyphenol rich diet include colon, prostate, epithelial, endometrial, and breast cancer.
The iron-chelating effects of EGCG (epigallocatechin gallate, a catechin), curcumin, myricetin, ginsenosides, and ginkgetin are thought to be an underlying mechanism through which polyphenols prevent neurotoxicity, leading to a neuroprotective effect against neurodegenerative diseases like Parkinson's Disease, Alzheimer's Disease, and Huntington's Disease.
Polyphenol-rich foods may boost your focus and memory. One study reports that drinking grape juice, which is naturally rich in polyphenols, helped significantly boost memory in older adults with mild mental impairment in as little as 12 weeks. Others studies suggest that cocoa flavanols may improve blood flow to the brain and have linked these polyphenols to improved visual and cognitive functions.
Type 2 diabetes
Several polyphenolic compounds, anthocyanins being the most substantiated, are associated with both the prevention and management of type 2 diabetes through protection of beta cells from glucose toxicity, anti-inflammatory and antioxidant effects, slowing of starch digestion, and regulation and altered transport of glucose, leading to better glycemic control. This happens through a slow breakdown of starch into simple sugars, lowering the likelihood of blood sugar spikes after meals.
A number of polyphenols have been shown to have protein-binding properties that can inhibit starch, lipid, and protein digestion in the gastrointestinal tract by interacting with and inhibiting digestive enzymes.
Today, choosing a healthy diet has become an essential part of healthy living and well being. As suggested, research studies have shown that the people who follow a polyphenol-rich diet are at a low risk for a range of chronic diseases, such as obesity, diabetes, some cancers, heart disease, etc.
Since fruits, especially apples, pears, apricots, cherries, berries, and grape, and vegetables, such as carrot, tomato, onion, garlic, cabbage, and celery, contain up to 200–300 mg of PCs per 100 g of their fresh weight, they can be used as dietary supplements of polyphenols.
The presence of phenolic compounds in foods has helped improved the perception of the concept of "quality of foods", rather than quantity (micronutrients over calories). These compounds have a low toxicity in the human body, and can therefore be considered a safe dietary element. Because of their antioxidant properties, phenolic compounds play a critical role in the oxidative stability of foods. Phenolic compounds are currently used in traditional and modern medicine in the design and development of new medicinal agents and for their extensive health benefits.
There is a popular idiom saying “You Are What You Eat” and truly, there is a close and positive relationship between a healthy diet and better health; this fact has been documented in a number of studies referenced in the list below.
Let food be thy medicine and medicine be thy food.