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A flavonoid a day keeps the doctor away

Analysis by Dr. Joseph Mercola Fact Checked

flavonoids foods

Story at-a-glance -

  • A 23-year study involving scientists from multiple countries found that the most prevalent causes of death, including malignancies and heart-related issues, are significantly lowered when flavonoids are eaten regularly
  • According to the CDC, heart disease, malignancies, stroke and diabetes are in the top seven most common causes of death in the U.S.
  • For the Danish Diet, Cancer and Health cohort, researchers spent 23 years scrutinizing the diets of 53,048 Danish people and found lower risks of death from cancer or heart disease when flavonoids were consumed
  • Another study found that when people who smoke and consume excessive amounts of alcohol eat more flavonoids, their risk for these diseases lowers, but that doesn’t mean harmful effects from those habits will disappear
  • More than 6,000 flavonoid compounds are found in plant-based foods, including several that are becoming more familiar to savvy consumers. These compounds include luteolin, quercetin, apigenin, catechin and anthocyanin

Flavonoids may not have the name recognition vitamins and minerals do, but as antioxidants with the power to fight disease and premature aging,1 plus decrease inflammation, they can make a dramatic difference in your health if you know where to find them.

Believe it or not, there are more than 6,000 distinct flavonoids, and every one of them communicates a unique benefit for your body. Found in fruits, vegetables, nuts and herbs, these phytonutrients have the capacity to prevent many of the most common illnesses in the world. Several of them are becoming more familiar to savvy consumers.2

Findings from a recent study collaboration between several researchers in Denmark and Australia, as well as one each from Northern Ireland and France, show you can lower your risk of developing heart disease, cancer and all-cause mortality when you regularly eat foods containing flavonoids.

The featured study, published in Nature Communications and known as the Danish Diet, Cancer and Health cohort, is the work of researchers who spent 23 years scrutinizing the diets of 53,048 Danish people. They found lower risks of death from cancer and heart disease in those who consumed more flavonoids. According to the scientists:

"A moderate habitual intake of flavonoids is inversely associated with all-cause, cardiovascular- and cancer-related mortality … The inverse associations between total flavonoid intake and mortality outcomes are stronger and more linear in smokers than in non-smokers, as well as in heavy vs. low-moderate alcohol consumers ...

Fruit and vegetable intakes are associated with a lower risk of cardiovascular disease (CVD), cancer, and all-cause mortality, with an estimated 7.8 million premature deaths worldwide in 2013 attributable to a fruit and vegetable intake below 800 (grams per) day."3

Can your risk of death be lowered?

According to the CDC,4 in 2016, heart disease topped the list of the leading causes of death in the U.S., with cancer in the second position. Stroke and diabetes — two of the five risk factors for metabolic syndrome that also raise your risk for heart disease — take the fifth and seventh slots.

But researchers at Edith Cowan University's School of Medical and Health Sciences in Australia looked at the data from the Danish Diet, Cancer and Health cohort and backed up the Danish cohort with a report5 that eating apples and drinking tea lower both cancer and heart disease risks. Both of those are high in flavonoids.

They also found a link between regular flavonoid consumption, drinking alcohol and smoking. People who were at a high risk of developing chronic diseases due to smoking and drinking more than two alcoholic drinks a day seemed to benefit the most from eating flavonoid-rich foods. Specifically, "Participants consuming about 500 [milligrams] of total flavonoids each day had the lowest risk of a cancer or heart disease-related death."6

However, even the Danish study listed negative effects from smoking and drinking; besides being carcinogenic, it's also damaging to endothelial and platelet function and culpable in such problems as thrombosis, inflammation and elevated blood pressure.7 An article in Health also didn't give a pass to people who excessively drink and smoke:

"That doesn't mean that eating flavonoid-rich foods will wipe out the harmful effects of excessive drinking and smoking, the researchers warn. But, the study found, it may help lower the risk of developing chronic diseases from these habits."8

Nicola Bondonno, lead researcher for the Edith Cowan University study, agreed that eating lots of flavonoid-rich foods won't outweigh the damage done by heavy tobacco and alcohol use, but that reducing them would at least help. She stressed that both habits damage blood vessels and increase inflammation, but flavonoid intake targets both of those specifically. She added:

"We know these (kinds) of lifestyle changes can be very challenging, so encouraging flavonoid consumption might be a novel way to alleviate the increased risk, while also encouraging people to quit smoking and reduce their alcohol intake."9

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Flavonoid intake: How much is enough?

According to Bondonno, about 500 milligrams (mg) of flavonoids were consumed by the study participants on a daily basis to lower their disease risks. She offered advice to replicate that outcome:

"It's important to consume a variety of different flavonoid compounds found in different plant based food and drink. This is easily achievable through the diet: one cup of tea, one apple, one orange, 100 [grams] of blueberries, and 100 [grams] of broccoli would provide a wide range of flavonoid compounds and over 500 mg of total flavonoids."10

The Danish study specified that 500 mg of flavonoid intake positively influenced outcomes for cardiovascular diseases, but with regard to cancer-related death, 1,000 mg per day was found to lower the "hazard ratios." Another point was significant regarding flavonoid intake for optimal health:

"That the thresholds for each of the flavonoid subclasses approximately sum to the threshold for total flavonoid intake is consistent with the idea that all are important and afford added benefit. Interestingly, these threshold levels exist well within daily dietary achievable limits … In this population it is likely that tea, chocolate, wine, apples, and pears were the main food sources of flavonoids."11

Flavonoids are abundant in most plant-based foods

Dark-hued fruits and vegetables as well as dark chocolate, red wine and tea typically provide ample flavonoids. There are six flavonoid categories, with similar names because of their chemical structure. It's important to note that the chemical structure of these compounds is also responsible for generating changes in bioactivity and metabolism, and that's where the health advantages are introduced. The Journal of Nutritional Science states:

"Flavonoids are associated with a broad spectrum of health-promoting effects and are an indispensable component in a variety of nutraceutical, pharmaceutical, medicinal and cosmetic applications. This is because of their antioxidative, anti-inflammatory, anti-mutagenic and anti-carcinogenic properties coupled with their capacity to modulate key cellular enzyme functions."12

Both the journal and the USDA database on flavonoids13 note several flavonoid classes and subclasses. They're listed below with examples of their sources and health benefits (with other studies cited):

Flavones — Luteolin is antitumor and anti-inflammatory; it blocks oxidative stress and is heart protective14 (found in Mexican oregano and rosemary); apigenin is beneficial for addressing diabetes, amnesia, Alzheimer's disease, depression, insomnia and cancer15 (found in celery, broccoli, green peppers, thyme, parsley, mint and oregano)

Flavonols — Quercetin and kaempferol contain antioxidants and lower your vascular disease risk (found in squash and spinach); myricetin and isorhamnetin inhibit tumors in breast cancer16 (found in bananas, apples, blueberries, peaches, pears, green tea, grape seeds and red peppers)

Flavan-3-ols — Catechin and epicatechin are known for their antimicrobial properties; epicatechin 3-gallate, epigallocatechin and epigallocatechin-3-gallate are most abundant in green tea, and are shown to both treat and prevent infections17; theaflavin, theaflavin 3-gallate and theaflavin 3'-gallate (found in chocolate and milk); epicatechin works as an insulin receptor activator and may exert "insulin-potentiating activity on the utilization of glucose"18

Flavanones — Hesperetin, or naringenin, a strong antioxidant, promotes gene expression, reduced adiposity (obesity) in animal models and is found useful in treating metabolic syndrome19) and eriodictyol; these are linked to free radical scavenging (found in all citrus fruits, such as oranges and lemons as well as grapes)

Anthocyanins — Cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin compounds have high levels of antioxidants; they are shown to be chemoprotective; they are also heart protective and neuroprotective and fight diabetes, inflammation and obesity; they also help vision20 (found in cranberries, black currants, dark-hued grapes, sweet potatoes and berries)

Isoflavones — Genistin, genistein, daidzein, glycetein and daidzin, also called phytoestrogens, protect cells against oxidative DNA damage; they may reduce your risk of osteoporosis21; studies show they may contribute to fewer instances of prostate cancer22 and breast tumors23 (found in soybeans (which should be non-GMO, organic and fermented for optimal health) and legumes, although consumption should be limited); which exert oestrogenic activity24

Studies on prominent flavonoids

A Harvard Health article says one reason avid tea drinkers are less prone to developing heart disease may be because of potency of the flavonoids in tea leaves. Part of the benefits of drinking tea, particularly for strengthening the blood vessels in your heart, stems from catechin and epicatechin compounds. Specifically:

"Research suggests that flavonoids help quell inflammation, and that in turn may reduce plaque buildup inside arteries. Green tea has slightly higher amounts of these chemicals than black tea ...

Short-term studies have shown that drinking tea may improve vascular reactivity — a measure of how well your blood vessels respond to physical or emotional stress. There's also evidence that drinking either black or green tea may lower harmful LDL cholesterol levels … Several large, population-based studies show that people who regularly drink black or green tea may be less likely to have heart attacks and strokes."25

A 2019 study found that the flavonoids in citrus fruits specifically are an example of how hard working and far reaching they are, notably zapping free radicals, improving both insulin sensitivity and glucose tolerance. They can break down fat for energy (lipid metabolism), decrease inflammation, fight obesity and improve endothelial function. All of these things lead to a healthier heart and improved blood sugar levels.26

In a study published in the Journal of Translational Medicine,27 it was observed that the more flavonoid-rich foods people eat, the less apt they are to develop heart disease, experience a nonfatal heart problem or die from heart disease. And from 12 studies used in a meta-analysis, it was reported in PLoS One28 that the incidence of breast cancer "significantly decreased" in women who reported a high intake of flavonols and flavones from their food.

For just one example of how powerful flavonoids are for your health, the one known as hesperetin in citrus fruits has alone exhibited dramatic health benefits, being "anticarcinogenic, antihypertensive, antiviral, antioxidant, antidiabetic, hepatoprotective [preventing liver damage], and anti-inflammatory."29

When you realize the real pharmacological mechanisms these compounds can jump-start, it becomes clear how important they are in treating and preventing diseases and infections in multiple areas of your body.