Written by:Roberta L. Duyff, MS, RD, FADA, CFCS
Food and Nutrition Consultant/President, Duyff Associates
SWEET CHERRIES... a wonderful short and sweet season makes these gems of nature a delicious summer snack. Nutritionally speaking, their benefits are well valued : good source of the antioxidant vitamin C and fiber; low in fat, including saturated fat;and sodium- and cholesterol-free. In any meal or snack, a serving of sweet cherries contributes good nutrition to any healthy eating score, with a modest amount of calories. Great for fitness-minded consumers!
Today's research is stepping beyond nutrients to uncover the phytonutrient story of sweet cherries - and how these bioactive nonnutritive plant substances contribute to health promotion and disease prevention.
In the bigger picture, fruits and vegetables contain thousands of phytonutrients with a myriad of properties. These properties might account, at least in part, for the many protective effects of fruit and vegetables, and the potential benefits of sweet cherries.
SWEET CHERRIES: THEIR PHYTONUTRIENT "SCORE"
Each fruit type and variety, as well as its growing environment, contribute to the unique phytonutrient profile of a specific fruit.
What's in sweet cherries? Although data on the phytonutrient composition is incomplete, research evidence has identified significant levels of phenolic compounds and other phytonutrients with antioxidant capacity.
One measure of antioxidant capacity in food is its ORAC (Oxygen Radical Absorbance Capacity) score. Cherries are among the ten highest ORAC fruits that are reported in tests by USDA's Agricultural Research Service (ARS). The ORAC score of sweet cherries is high - 580 (for about 3.5 ounces) - similar for many citrus fruits, but significantly less than berries; ARS reports a general score for cherries of 670. Studies suggest that eating plenty of high-ORAC foods can raise the antioxidant power of blood 10 to 25 percent. (Note: besides antioxidant substances, other plant substances or combinations of plant substances may also account for the benefits of high ORAC foods.)
Because of their antioxidant activity, phenolic compounds in fruits and vegetables have generated a great deal of interest. Phenols, including flavonoids, protect body cells against ("anti-") the damage caused by oxygen ("oxidation") that's released as a by-product of energy metabolism. A small amount of released oxygen becomes part of highly reactive free radicals, which attack and damage body cells to get the missing electron they need. Antioxidants protect by contributing an electron of their own. In so doing, they neutralize free radicals and help prevent cumulative damage to body cells and tissues.
Much of the total antioxidant activity of fruits and vegetables is related to their phenolic content, not only to their vitamin C content. Research suggests that many flavonoids are more potent antioxidants than vitamins C and E.
"A handful of cherries a day keeps the doctor away." In part, that may be true. Like apples, cherries are relatively high in a flavonoid called quercetin. A serving of processed cherries has about the same amount of quercetin as an apple: about 3 milligrams of quercetin for 3.5 ounces or apple or processed cherries.* Because processing concentrates the quercetin, processed cherries have about twice the amount of quercetin as fresh cherries.
(*An average apple has about 36 milligrams quercetin per kilogram; 1 kilogram of processed sweet cherries has about 32 milligrams quercetin.)
Research on quercetin - specifically on quercetin and isoquercitrin - has revealed that the profile of these flavonoids varies among different types of cherries. Sweet cherries and tart Montmorency cherries are similar in their isoquercitrin content; however, tart cherries have a significantly higher amount of quercetin. Quercetin, the most commonly consumed flavonoid, is reported to have a strong antioxidant capacity. It has been studied for its potential health benefits, particularly for its relation to blood clotting and its role in reduced risk for heart attack and stroke.
Fruit pigments, which account for the varying colors of cherries and berries, guava and citrus, have been described as a potential "mother lode in a gold mine of antioxidants": among pigments, the rich red hue of sweet cherries contributed by anthocyanins. Actually, anthocyanins are among the large group of flavonoid pigments responsible for most of the red, blue, and intermediate colors in flowers and fruits; these pigments attract insects and other animals for the purpose of pollination or seed distribution.
Cherries have a high ORAC score, which seems to be correlated with their anthocyanin content. Not surprisingly, the darker the cherry, the higher the anthocyanin content. The range is about 80 to 300 milligrams of anthocyanins in 3.5 ounces (100 grams) of pitted dark cherries, compared with 2 to 40 milligrams of anthocyanins in the same amount of light-colored cherries.
Research suggests that processing degrades the anthocyanin content of cherries, reporting a loss of more than 50 percent of anthocyanins in cherries during 6 months of frozen storage.
No recommended intake currently exists for anthocyanins, however, people in the United States consume about 200 milligrams of anthocyanins daily. Sweet cherries - as snacks or in salads, side dishes, desserts, and smoothies - can make a significant contribution to the daily intake.
Cherries contain yet another phenolic compound, ellagic acid. Found in many fruits, ellagic acid may help the growing plant fight microbial infection; it's also part of cancer-preventing drugs.
another classification of phytonutrients, terpenes (which include the well-known carotenoids) also work as powerful antioxidants. Monoterpenes are found in the essential oils of fruits; cherries are reported to be a significant source of the monoterpene perillyl alcohol. Some dietary monoterpenes are reported to show antitumor activity.
You've seen melatonin tablets, sold on the supplement shelf, perhaps in a 500-micogram tablet with a cherry flavor. Did you know that melatonin is found naturally in food as well! In fact, cherries are a significant source, with tart cherries supplying more than sweet cherries. For 100 grams (about 3.5 ounces) of dried cherries, tart Montmorency cherries contain 27 milligrams of melatonin compared with 7 milligrams in sweet cherries. Although known for its potential as a sleep enhancer, it's reported that melatonin also possesses high antioxidant activity, perhaps being amore effective than vitamin E in scavenging peroxyl radicals, one type of free radical.
Unlike antioxidant vitamins, melatonin is soluble in both water and fat, perhaps enhancing its capacity as an antioxidant.
Cherries contain beta-sitosterol - a phytosterol, or plant sterol, found in fruits, such as avocados, bananas, apples, cantaloupes, grapes, and plums, as well as cherries. High phytosterol intake may be linked to lower blood cholesterol levels.
Note: FIBER. An undigestible carbohydrate, fiber offers a functional health benefit as well. Like other fruits, cherries supply fiber: 10 cherries contain about 1.6 grams of fiber (1.1 grams of insoluble fiber and 0.5 grams of soluble fiber.) For healthy adults, 20-35 grams of fiber daily are advised. A high-fiber diet is linked to reduced risks for many health problems, including some cancers and heart disease.
SWEET CHERRIES: THEIR POTENTIAL "PHYTO-BENEFITS"
Due to their biological action and perhaps interactions that affect bioactivity, the phytonutrients in fruits and vegetables are thought to reduce the risk of several chronic health problems, for example heart disease and some cancers. the phytonutrients in cherries may offer these benefits:
Promote cardiovascular health
By contributing to antioxidant activity, flavonoids in cherries and other fruits may help protect against heart disease and strokes. Antioxidants are thought to inhibit the oxidation of LDL ("bad") cholesterol; LDL oxidation may promote atherosclerosis. It's worth noting that cherries, like red wine, contain large amounts of an anthocyanin 3-glucoside (C3G); C3G may contribute to the low incidence of heart disease, despite higher fat intake, reported in France. Although not clear in human studies, in vitro research also suggests that flavonoids may inhibit blood platelets (the blood cells responsible for blood clotting) from aggregating (forming a clot) and adhering.
Promote against cancer
In 1992, the National Cancer Institute's 5 A Day For Better Health program recognized the importance of fruits and vegetables as part of cancer prevention, most notably cancers of the alimentary tract, although they may offer protection from other cancers as well. the antioxidant activity from flavonoids may offer anticancer protection. Of the may phenolic compounds, anthocyanins may be the most potent, although the data to support the anticancer role of anthocyanins and of flavonoids overall is limited. Epidemiological studies suggest that consuming quercetin-rich foods may be associated with a reduced risk of lung cancer. In animal studies, ellagic acid and perillyl alcohol - both found in sweet cherries - also appear to have anticancer effects. Cherries insoluble fiber may help reduce the risk for certain cancers, e.g., breast and colon cancer. Although there's no research evidence yet with sweet cherries, studies with tart cherries suggest that they contain substances that substantially reduce the formation of heterocyclic aromatic amines (HCAAs), when the ground cherries are added to ground meat and then the meat is cooked with dry heat; HCAAs may be carcinogenic.
Besides its potential antioxidant benefits, melatonin in cherries may help influence sleep patterns. Sweet cherries provide a significant amount of melatonin, although not as much as tart Montmorency cherries.
Early research with animal studies suggest that eating plenty of fruits and vegetables with a high ORAC score may help slow the processes linked to aging of the body and brain.
Other potential health-enhancing benefits
Other areas of research are exploring potential health benefits from phytonutrients, including those present in cherries:
--Pain-relieving compounds, e.g., cox inhibitors, which may be present in cherries; research is underway involving tart cherries and their ability to relieve cancer pain.
--Anti-inflammatory properties of certain anthocyanins and other flavonoids, which may relieve arthritis symptoms; research is underway with tart cherries.
--Treatment for diabetes and ulcers with orally administered anthocyanins.
--Potential role of antioxidants in preventing macular degeneration.
Sweet Cherries: A Perspective
To put this in perspective, with food composition data on antioxidants and other phytonutrients incomplete--and limited data on their bioavailability, actions, variability, and interactions -- we can only expect that research will reveal a broader phytonutrient story for sweet cherries and other fruits in the future.
It is important to remember that the intake of many phytonutrients, including flavonoids, is associated with other dietary factors, such as antioxidant vitamins (e.g., vitamin C), fiber, and less fat. For many reasons, isolating the health-promoting benefits of a single phytonutrient or the full complement of phytonutrients in sweet cherries is challenging. Regarding their action, little is known about the effects of processing or cooking on phytonutrients.
Regardless, an increasing body of scientific evidence is almost certain to further support the many dietary guidelines released since 1977 that encourage Americans to eat more fruits and vegetables!
Sweet Cherries: Sources
Craig, Winston J. 'Phytochemicals: Guardians of Our Health,' A continuing education article, Andrews University, Berrien Springs, Michigan.
Kahkonen, Mara P., Hopia, Anu I., Vuorela, Heikki J., Rauha, Jussi-Pekka, Pihlaja, Kalevi, Kujala, Tytti S., and Heinonen, Marina. 'Antioxidant Activity in Plant Extracts Containing Phenolic Compounds, Journal Agriculture and Food Chemistry, 1999, 47: 3954-3962.
Katan, M.B. 'Flavonoids and Heart Disease,' American Journal of Clinical Nutrition, 1997, 65:1542-3.
Messina, Mark. 'A Healthy Look at Sweet Cherries,' Washington State Fruit Commission and journal articles cited in this publication.
Ou, Boxin. 'Characterization of Natural Antioxidants from Montmorency Cherries, Balaton Cherries and Sweet Cherries,' Unpublished report, Brunswick Laboratories, Wareham, Maine, April, 2000.
USDA Human Research Center on Aging at Tufts, 'Human Nutrition: Foods that score high in an antioxidant assay called ORAC may protect cells and their components from oxidative damage,' Agricultural Research Service Quarterly Report, January- March 1999.
Wrolstad, Ronald E. 'The Possible Health Benefits of Anthocyanin Pigments and Polyphenolics,' The Linus Pauling Institute, Oregon State University.