Reprinted with the kind permission of Dr. Mercola.
By Dr. Mercola
Authors of a literature review involving data collected from more than 602,000 individuals across Australia, Europe and the U.S. assert anthocyanins, a flavonoid pigment found in a variety of fruits and vegetables, may lower your risk of cardiovascular disease, as well as help in the treatment of certain types of cancer and diabetes.
Researchers suggest about 400 individual anthocyanins have been identified, most of which are concentrated in the skins of fruits, particularly berries such as blueberries, raspberries and strawberries. Let’s take a closer look at this important class of health-boosting flavonoids.
High Intake of Anthocyanins May Lower Your Risk of Cardiovascular Disease
A literature review and meta-analysis published in the journal Critical Reviews in Food Science and Nutrition1 suggests anthocyanins, the water-soluble pigments known to give certain fruits and vegetables their distinctive blue, purple and red hues, may also help reduce your risk of cardiovascular disease and aid in the treatment of other illnesses.
According to Johns Hopkins Medicine, an estimated 84 million Americans suffer from some type of cardiovascular disease, which is attributed to one out of every three deaths in the U.S.2 The study authors analyzed data collected from 19 prospective cohort studies, with a focus on evaluating the effect of anthocyanins on circulatory and heart health.
The research involved more than 602,000 individuals from across Australia, Europe and the U.S., who were monitored for periods ranging from four to 41 years.3 Compared to those with the lowest intake, the researchers noted participants with the highest anthocyanin intake were:4
- 9 percent less likely to suffer from coronary heart disease
- 8 percent less likely to die from causes associated with heart disease
That said, the study authors noted the absence of any relationship between the intake of anthocyanins and a reduced risk of heart attack or stroke.5 About the research, professor Glyn Howatson, Ph.D, director of research and innovation for the department of sport, exercise and rehabilitation at the U.K.’s Northumbria University, said:6
“Our analysis is the largest, most comprehensive evaluation of the association between dietary anthocyanin intake and the risk of cardiovascular disease. Evidence has been growing in recent years to suggest these natural plant compounds might be especially valuable for promoting cardiovascular health.”
What Are Anthocyanins and Where Are They Found?
Anthocyanins are a class of flavonoids — natural antioxidants known to protect your body from cellular degeneration.
Authors of a 2010 study commented, “Approximately 400 individual anthocyanins have been determined. They are generally more concentrated in the skins of fruits, especially berry fruits. However, red berry fruits, such as strawberries and cherries, also have anthocyanins in their flesh.”7 Fruits noted for their high anthocyanin content include:8
- Acai berries
- Black currants
- Red or purple grapes
Vegetables containing anthocyanins include:9
- Red cabbage
- Red onion
- Certain types of potatoes
A body of 2010 research published in the journal Nutrition Reviews suggests anthocyanin content is usually proportional to the color intensity of the fruit or vegetable in which it is found, ranging from 2 to 4 grams (g)/kilogram per item and increasing as the produce ripens.10
The study authors note the levels of polyphenols, including anthocyanins, found in berries (and therefore the potential impact of berry consumption on your heart health) are affected by post-harvest processing methods such as drying, pasteurization and pressing.11
As you may expect, the highest levels of anthocyanins will be found in the whole fruit. The researchers further claim Americans consume an average of 12.5 to 215 milligrams of anthocyanins per day, while asserting, “Berry anthocyanins are poorly bioavailable, are extensively conjugated in the intestines and liver and are excreted in urine within two to eight hours post consumption.”12
Given the poor bioavailability, it does not make sense to overconsume berries or any other potential food source of anthocyanins. Due to the ongoing nature of research on anthocyanins and other flavonoids, it seems best to wait until more definitive conclusions are drawn about the many benefits associated with them.
Other Studies Demonstrate the Value of Anthocyanins for Heart Health
The author of an earlier study on anthocyanins suggested they are prized for their many biological functions, including their well-known anticarcinogenic, anti-inflammatory, antimicrobial and antioxidant activities.13 He asserted they “display a variety of effects on blood vessels, platelets and lipoproteins,” as well, making them useful to reduce your risk of coronary heart disease.14
The authors of the 2010 research mentioned above claim studies using blueberries, cranberries and strawberries have demonstrated “significant improvements in [low-density lipoprotein (LDL)] oxidation, lipid peroxidation, total plasma antioxidant capacity, dyslipidemia and glucose metabolism” in both healthy subjects and participants dealing with metabolic risk factors.15
As to the manner in which berries, as a source of anthocyanins, influence your health, the study authors said, “Underlying mechanisms for these beneficial effects are believed to include upregulation of endothelial nitric oxide synthase, decreased activities of carbohydrate digestive enzymes, decreased oxidative stress and inhibition of inflammatory gene expression and foam cell formation.”16 Based on the evidence, they concluded berries are an essential addition to a heart-healthy diet.
Anthocyanins in Blueberries and Strawberries Is Shown to Lower Your Blood Pressure
Blueberries and strawberries, both of which are rich in anthocyanins, have been highlighted for their role in helping protect your heart and lower your blood pressure. Past research revealed women ages 25 to 42 who ate more than three servings per week of blueberries and strawberries had a 32 percent lower risk of having a heart attack.17
That is likely so because anthocyanins are known to benefit the endothelial lining of your circulatory system, possibly preventing plaque buildup in your arteries, as well as promoting healthy blood pressure.
Other research has shown these antioxidants protect against heart disease by reducing oxidative stress and inflammation, while enhancing capillary strength and inhibiting platelet formation.18 Eating blueberries has also been shown to lower your blood pressure.
A study published in the Journal of the Academy of Nutrition and Dietetics19 involving postmenopausal women suggests blueberry consumption positively affects blood pressure. The women, who had either prehypertension or hypertension, received a placebo powder or freeze-dried blueberry powder (an amount equivalent to about 1 cup of fresh blueberries) daily for eight weeks.
While the placebo group saw no significant changes, the women supplementing with blueberries realized a 5 to 6 percent drop in both their systolic (top number) and diastolic (bottom number) blood pressure readings. Measurements of nitric oxide were also significantly increased in the blueberry group.
Nitric oxide helps your blood vessels maintain their elasticity and also dilates your blood vessels, thereby reducing your blood pressure. The study authors stated: “Daily blueberry consumption may reduce blood pressure and arterial stiffness, which may be due, in part, to increased nitric oxide production.”20
Anthocyanins May Aid in Treatment of Colon Cancer
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In a study published in Scientific Reports, 21 researchers from the University of Eastern Finland, working in conjunction with the U.S. National Institute on Aging, noted the promising role anthocyanins may play in cancer treatment.
The study focused on the effect of berry pigment on sirtuins — a type of protein involved in regulating your body’s cellular processes with respect to DNA repair, inflammation response reduction, longevity and metabolism.
Specifically, the study highlighted the effects of anthocyanins on a lesser-known sirtuin referred to as SIRT6, which has been linked to glucose metabolism.22 Given the study outcomes, it’s possible the regulation of this enzyme could open up new avenues for cancer treatment.
“The most interesting results of our study relate to cyanidin, which is an anthocyanin found abundantly in wild bilberry, blackcurrant and lingonberry,” said lead study author Minna Rahnasto-Rilla, who holds a doctorate in pharmacy at the University of Eastern Finland.23 Specifically, the researchers noted cyanidin:24
- Increased SIRT6 levels in human colorectal cancer cells
- Decreased the expression of the twist-related protein (Twist1) and glucose transporters (GLUT1) cancer genes
- Increased the expression of the tumor-suppressor forkhead box O3 (FoXO3) gene in cells
These findings show anthocyanins like cyanidin can increase the activation of SIRT6, and thereby reduce the expression of cancer genes and cancer cell growth.
Prostate Cancer Also Impacted Positively by Anthocyanins
Researchers have long thought differences in diet — particularly the consumption of wine, which contains anthocyanins and other beneficial polyphenols — may explain the high rates of prostate cancer in the U.S. as compared to other regions.
Given the fact about 164,000 new cases of the disease were expected to be diagnosed in 2018 and more than 29,000 American men die of prostate cancer annually, this disease is a real concern. 25
The Mediterranean diet, on the other hand, which is rich in fish and olive oil, as well as healthy amounts of fruits, nuts and vegetables, is thought to act as a natural cancer inhibitor. About the impact of flavonoids like cyanidin and kaempferol, authors of a study published in the Journal of Nutritional Biochemistry said: 26
“Epidemiological evidence indicates that polyphenolic compounds in diets are protective against cancer, and cyanidin and kaempferol are abundant in wine and plants.
Therefore, the objective of the investigation was to determine the effects of cyanidin and kaempferol on prostaglandin E2 (PGE2) and cyclooxygenase-2 (COX-2) protein levels, and if peroxisome proliferator-activated receptor gamma (PPARgamma) and nuclear factor kappaB (NFkappaB) are involved in the expression of COX-2 in prostate cancer cells.”
What they found was that the anthocyanin cyanidin lessens PGE2 production and COX-2 expression in human prostate cancer cells.
The study authors stated, “Cyanidin and kaempferol … reduced the level of PGE2 in … cell cultures and also attenuated the effect of arachidonic acid on increasing the amount of PGE2. Cyanidin reduced the levels of COX-2 protein in a dose- and time-dependent fashion.” 27
Beyond that, a 2015 study published in the International Journal of Oncology 28 found cyanidin induced cell death and differentiation in prostate cancer cells. About the results, the researchers said: 29
“[C]ompounds like polyphenols, capable of inducing differentiation may represent potential chemotherapeutic agents.
We show for the first time that C3G, the most abundant anthocyanin in the human diet, inhibits cell growth and cell viability, resulting in the reversion of both androgen-sensitive (LnCap) and of the androgen-independent (DU145) [prostate cancer] cells from a proliferating to a differentiated state.”
Can Anthocyanins Help Prevent and Control Diabetes?
The significance of anthocyanins in the prevention and treatment of Type 2 diabetes was highlighted in a 2018 literature review conducted at the Wroclaw Medical University in Poland.30
The study authors reviewed previous research related to the importance of anthocyanins in regulating carbohydrate metabolism and reducing insulin resistance as major factors in lowering the risk of Type 2 diabetes. According to the team, to date, a number of studies involving humans and animals have demonstrated anthocyanins:31
- Enhance the secretion of adiponectin and leptin
- Fuel the activation of adenosine monophosphate (AMP)-activated protein kinase
- Increase the activation of PPARγ in adipose tissue and skeletal muscles
- Inhibit intestinal alpha-glucosidase and pancreatic alpha-amylase
- Reduce retinol binding protein 4 (RBP4) expression
- Regulate glucose transporter type 4 (GLUT4) gene expression and translocation
Additionally, anthocyanins were found to improve insulin secretion by rodent pancreatic beta cells. Because individual anthocyanins and their glycosides have different activity, the researchers recommended eating a variety of plant products as part of your daily diet to ensure you are getting a wide range of anthocyanins.
Get the Benefits of Anthocyanins but Watch Your Daily Fructose Intake
While berries and other colorful fruits are both tasty and nutrient-rich, I continue to recommend you eat them in moderation. Even though whole fruit contains natural sugars, for optimal health, you must limit your fructose consumption. As such, I advise you keep your total fructose intake below 25 g daily, including fructose from whole fruit.
If you have diabetes, heart disease, high blood pressure or insulin resistance, you’d be wise to limit your daily intake of fructose to 15 g until your condition improves. As noted in the Environmental Working Group (EWG) video above, because most berries and thin-skinned fruits (and vegetables) are sprayed with pesticides, it’s always best to buy organic or grow your own.
For more information on the importance of buying organic, check out the EWG’s Dirty Dozen list.
As mentioned earlier, it would be unwise to overindulge in berries and other food sources of anthocyanins until more conclusive studies are completed.
As one researcher stated, “[U]ntil the absorption and metabolic fate of anthocyanins in vivo is unraveled, it would be unwise to conclude a high consumption of them will reduce the risk of chronic diseases. Long-term intervention trials must be properly designed and carried out to provide definite proof.”33
For now, to achieve optimal health, it’s best to eat a balanced diet from whole food sources. Be sure to include a variety of anthocyanin-rich foods in moderation. Because diet is just one factor known to contribute to your well-being, I also advise you to lower your stress level and get plenty of exercise and sleep, too.
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Sources and References
- 1, 4, 5 Critical Reviews in Food Science and Nutrition October 2, 2018 [e-Pub ahead of print]
- 2 Johns Hopkins Medicine, Cardiovascular Disease Statistics
- 3, 8, 9 Medical News Today November 7, 2018
- 6 PRNewswire November 5, 2018
- 7, 10, 11, 12, 15, 16 Nutrition Reviews March 2010; 68(3): 168–177
- 13, 14, 33 Annals of the Institute of Higher Health February 2007; 43(4): 369-374 [PDF]
- 17 Circulation January 15, 2013;127(2):188-96
- 18 Journal of Biomedicine and Biotechnology December 1, 2004; 2004(5): 306-313
- 19, 20 Journal of the Academy of Nutrition & Dietetics March 2015; 115(3): 369–377
- 21 Scientific Reports March 7, 2018; 8(1)
- 22, 24 Science Daily April 5, 2018
- 23 EurekAlert! April 5, 2018
- 25 American Cancer Society January 4, 2018
- 26, 27 Journal of Nutritional Biochemistry September 2006; 17(9): 589-596
- 28, 29 International Journal of Oncology October 2015; 47(4):1303-1310
- 30, 31 Advances in Clinical and Experimental Medicine (Wroclaw Medical University, Poland) January 2018 27(1): 135-142
- 32 NoGrainer.com, Fructose Content of Common Fruits Chart