Super Fruits: The Power of Polyphenols

Phytonutrients, from phyto, meaning "plant" in Greek, are certain organic compounds known to promote human health, though most are not essential for life. The major classifications of phytochemicals in foods are polysaccharides, terpenes, organic sulfurs, organic acids, amines and polyphenols. Recent evidence demonstrates that plant polyphenols have numerous benefits, including helping improve endothelial function, inhibiting abnormal platelet aggregation, supporting healthy blood lipids, fighting inflammation, quenching free radicals, enhancing endogenous antioxidant enzymes, and up-regulating cyclic AMP (cAMP) and mitochondrial biogenesis.¹ In 2005, The 1st International Conference on Polyphenols and Health strongly suggested consuming more polyphenols for helping prevent degenerative diseases, especially cardiovascular disorders and cancer.² It is therefore not surprising that fruits and berries rich in polyphenols, and the extracts, are being marketed as "super fruits."

Polyphenols may be subclassified as non-flavonoids and flavonoids, with the following foods reflecting polyphenol content of each subclassification:

• Non-flavonoids: ellagic acid (strawberries, blueberries, raspberries), stilbenes (resveratrol in grape skins, peanuts, Japanese knotweed, aka Polygonum cuspidatum).
• Flavonoids: anthocyanins (purple, red/purple, and blue fruits and berries, purple cabbage, beets, grape seed extract); catechins (tea, wine, cocoa, coffee); flavanones (citrus bioflavonoids); flavones (fruits and vegetables); flavonols (fruits and vegetables, tea, wine, onion, apple skin, quercetin); isoflavones (soybeans).

Functional foods and drinks fortified with so-called "super fruits" are usually very high in polyphenols, and well they should be considering the indications of their vast array of potential benefits, as briefly touched upon from the following small sample of the plethora of current scientific studies.

What the Research Is Saying

Extracts from black currants, rich in anthocyanins, may reduce inflammation in the lungs and potentially offer benefits to the increasing number of asthmatics - perhaps best in the form of functional foods, according to researchers.³ Antioxidant-rich extracts of blueberries in a dose-dependent manner may counter the detrimental effect of oxidative stress caused by excessive exercise.⁴

A water-soluble citrus bioflavonoid mixture, without added vitamin C, was found capable of inhibiting the increased capillary permeability caused by an inflammatory exudate, acting as an anti-inflammatory over a larger pH range of exudates than even cortisone.⁵ Orange juice, naturally rich in citrus bioflavonoids, may help prevent the negative effects of the free radical and endotoxin cascade that follows a high-fat, high-carbohydrate meal.⁶ Berries (bilberries, black currants, cranberries and strawberries) rich in polyphenols decreased the postprandial glycemic response of sucrose in healthy subjects, adding more evidence to their potential for lowering risk of obesity, diabetes and cardiovascular disease (CVD).⁷

Data was just presented as part of the scientific program of the American Society for Nutrition at the Experimental Biology Convention (April 2010) in Anaheim, Calif., showing that extracts from the chokeberry, which contains five times the amount of flavonoids and anthocyanins as cranberries, may prevent weight gain in pre-diabetics and affect genes linked to the development of fat tissue and related inflammatory pathways. Furthermore, the chokeberry-supplemented group was found to have lower blood glucose and reduced levels of plasma triglycerides, cholesterol, and low-density lipoprotein (LDL) cholesterol. Together, these findings suggest potential in lowering heart disease and diabetes risk. Other studies have shown that black chokeberry tends to regulate immune function in patients with breast cancer, suppress the growth of human colon cancer cells, allow less oxidative damage to red blood cells during vigorous exercise and lower blood pressure 11 mmHg systolic and 7 mmHg diastolic.^8-10

Another study presented at the Experimental Biology Convention in Anaheim showed that grape consumption lowered blood pressure, improved heart function and reduced other risk factors for heart disease and metabolic syndrome, such as reduced inflammatory indicators in the heart and blood, lower triglycerides and improved glucose tolerance. "The possible reasoning behind the lessening of metabolic syndrome is that the phytochemicals were active in protecting the heart cells from the damaging effects of metabolic syndrome," said presenter Steven Bolling, MD, heart surgeon at the University of Michigan Cardiovascular Center and head of their Cardioprotection Research Laboratory.

Resveratrol, naturally rich in grape skins, is a polyphenol that Harvard researchers discovered led to a 25 percent increase in lifespan in mice. Furthermore, studies from France showed that mice fed resveratrol did not gain weight as compared to controls when given a high-fat and high-calorie diet. Beyond this, a number of other studies have demonstrated the non-flavonoid polyphenol resveratrol to have antioxidant, anti-cancer, anti-inflammatory, and cardioprotective properties.¹¹ Resveratrol, along with quercetin, also increases cyclic AMP through mitochondrial biogenesis, which likely relates to their life-extending and sports-performance-enhancing properties.¹²

The high polyphenol (procyanidin) content of apples is largely responsible for their ability to lower blood cholesterol, inhibit triglyceride absorption and abdominal fat accumulation, and enhance insulin sensitivity.^13-16 In addition, apple polyphenols have the potential to reduce allergic conditions by blocking the release of histamine.^17-22

Grape seed extract contains high levels of procyanidin dimers that have been shown to be potent inhibitors of aromatase, displaying potential usefulness in the prevention/treatment of hormone-dependent breast cancer.²³ Polyphenol-rich pomegranate juice possesses anti-atherosclerotic and anti-hypertensive properties, acting both as a powerful antioxidant and as an angiotensin converting enzyme (ACE) inhibitor, lowering systolic blood pressure by 5 percent.²⁴

Super-Fruit Synergy?

Indian gooseberry, aka amla fruit, has been shown to reduce the effect of aging on renal dysfunction related to oxidative stress and significantly reduce systolic blood pressure. Amla may therefore useful for the prevention of age-related renal disease.^25-26 Amla has also been shown to help protect smokers and benefit as a natural skin care ingredient.^27,28

By itself, a vegetable fatty acid form of vitamin C with bioflavonoids has been shown to possess the best absorption and retention rates of any commercial form of vitamin C.^29-30 It is more rapidly absorbed and leads to higher serum vitamin C levels and greater duration of elevated serum vitamin C.^31-32 However, when this new vegetable fatty acid form of vitamin C with bioflavonoids is mixed together with amla fruit extract in an aqueous solution, the combination has displayed greater antioxidant capacity than was predicted based on the sum of their individual antioxidant values.³³

Polyphenols: The More the Merrier?

Even polyphenols from different plants seem to work synergistically when consumed together, with benefits from the combination again equaling more than the sum of the parts.³⁴ For example, amla has been shown to increase the antioxidant power of other polyphenols (anthocyanins in pomegranate), in a dose-dependent manner in both in vitro and ex vivo models.³⁵

Indeed, in a very recent study, concentrates of berry powder (bilberry, blackberry, black currant, blueberry, cranberry, Concord grape, elderberry, raspberry and red currant) plus a vegetable powder (acerola cherry, apple, beet, broccoli, cabbage, carrot, cranberry, kale, orange, peach, papaya, parsley, pineapple, spinach, and tomato) have been shown to reduce inflammatory biomarkers by between 16 percent and 35 percent. The authors concluded, "The close relationship between chronic inflammation and poor human health, suggests such a juice concentrate is a beneficial addition to the habitual diet in support of human health."³⁶

Mother Nature's bounty of polyphenols appears to combat free-radical damage and inflammation, thereby potentially lowering the risk of cardiovascular disease, high blood pressure, diabetes, cancer, and all-too-common allergic conditions. Furthermore, it appears that taken together, the sum of potential protections and benefits is greater than the individual food, extract or supplement.

The take-home message is nothing new, but it certainly bears repeating. Almost everyone should consume 7-9 daily servings or more of fruits and vegetables of all the colors. This includes the polyphenols that are generally richest in the red/purple berries, pomegranates and blueberries. For those desiring the benefits of polyphenols, but for whatever reason must avoid them or find it difficult to consume them daily (which is always the best way), current science appears to support supplementing with fruit and vegetable juice powders rich in polyphenols as the next best thing.

References

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26. Ibid.
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34. Barclay L, Op Cit.
35. NutraGenesis, Op Cit.
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