Written by: Cynthia Thomson, PhD, RD, Department of Nutritional Sciences,
and Chieri Kubota, PhD, Department of Plant Sciences, at the University of Arizona
Diets rich in fruits and vegetables are known to reduce the risk of chronic diseases including cancer, cardiovascular disease, diabetes, obesity or select inflammatory disorders. While data on the specific health benefits of cherries is limited, in recent years the U.S. Department of Agriculture has expanded its bioactive food component database to include an analysis of anthocyanin content of select plant foods, and sweet, fresh cherries are considered to be significant sources of anthocyanins in the human diet.
Sweet cherries have several cancer-preventive components including fiber, vitamin C, carotenoids and anthocyanins. The potential role of sweet cherries in cancer prevention lies mostly in the anthocyanin content, especially in cyanidin. Sweet cherries are a good source of cyanidins, which appear to act as an antioxidant and in this role may reduce cancer risk. In a study by Acquaviva et al, a significant increase in free radical scavenging was demonstrated with exposure to cyanidin (Acquaviva, 2003) and a separate study using human cancer cell lines demonstrated cell cycle arrest and apoptosis of mutated cells exposed to cherry anthocyanins (Lazze, 2004; Shih, 2005). Further research suggests that the growth arrest characteristics of cyanidin are likely, at least in part, to be a result of significant inhibitory effects of these cherry components on epidermal growth factor receptors (Meirers, 2001). Finally, there is compelling evidence from basic science that cyanidin may also promote cellular differentiation and thus reduce the risk for healthy cells to transform to cancer (Serafino, 2004).
The role of red wine in reducing the risk of cardiovascular disease has been studied widely for more than 20 years, and studies suggest anthocyanin found in red wine has important biological effects that reduce cardiovascular disease risk (Corder, 2006). This includes protecting lipids from oxidant damage and cardiovascular vessel plaque formation, anti-inflammation, nitric oxide formation and vascular dilation. Similarly, sweet cherries have been shown to have significant levels of anthocyanins as well as other pigments in perhaps smaller concentrations that together provide synergistic effects thought to be protective to heart and related vascular tissue (Reddy, 2005).
Evidence suggesting a protective role for cherries for diabetes is relatively rare, but researchers are interested in the role of anthocyanins in reducing insulin resistance and glucose intolerance. In one study, cells exposed to various glucose loads and then exposed to anthocyanins and anthocyanidins showed increased insulin production, suggesting the role of these compounds in blood glucose control should be explored further (Jayaprakasam, 2005). The study suggested that the bioactive compounds found in cherries are responsive, in terms of enhanced insulin production, to a glucose-rich environment and work to control glucose levels.
Recently the role of the glycemic index in diabetes control has gained renewed interest. Sweet cherries have an estimated glycemic index of 22, generally lower than other fruits including apricots (57), grapes (46), peaches (42), blueberries (40) or plums (39). The lower glycemic index makes sweet cherries a potentially better fruit-based snack food (as compared with many other fruits) for people with diabetes. The lower glycemic response shown in relation to cherry consumption may be the result of glucose-lowering effects of cherry phytochemicals in combination with the relatively modest fiber content of cherries.
Other Potential Health Promoting
An important new area for nutrition research is the role of naturally occurring compounds, primarily in plant foods, to modify the inflammatory process in humans. Low-grade inflammation is a potential risk factor for a wide range of chronic illnesses including cancer, cardiovascular disease, and arthritis. In addition, obesity has been shown to be associated with elevated inflammatory response. While Americans are often advised to take low-dose aspirin to offset this problem, researchers are looking for new ways â€¡¡ã such as diet modification â€¡¡ã to enhance anti-inflammatory response.
Select phytochemicals in cherries have been shown to inhibit the cyclooxygenase (COX) enzymes responsible for inflammatory response. In a cell culture study assessing COX-1 and -2 enzyme activity, the anthocyanin cyanindin, common to sweet cherries, along with malvidin, were shown to have the greatest inhibitory effects (Seernam, 2003). In relation to anti-inflammatory properties, cherries have been investigated in relation to pain control. Evidence suggesting a role of dietary constituents in reducing pain is limited, but remains an active area of research. (Tall, 2004).
Flavonoids and procyanidin compounds have been shown to reduce oxidant stress and -amyloid production and may indirectly reduce the risk for Alzheimerâ€™s disease (Yoshimura, 2003; Heo, 2004). Recent studies have shown the potential role of sweet cherry phenolic compounds in protecting neuronal cells involved in neurological function. The phenolics in sweet cherries include both quercetin and hydroxycinnamic acid as well as anthocyanins. One study exposed neuronal cells to a variety of phenolic compounds found in sweet and tart cherries and showed that total phenolics, and predominantly anthocyanins, demonstrated a dose-dependent reduction in oxidant stress (Kim, 2005). Further study into possible protective effects of sweet cherry bioactive compounds in reducing risk for, or morbidity related to, Alzheimerâ€™s disease is warranted.