The conventional wisdom that “an apple a day keeps the doctor away” has evolved into something more sophisticated today. Now, it’s blueberries boost memory, cranberries help prevent urinary tract infections, or grape seed extract helps prevent heart disease.
It has always been known that fruits are an essential part of a healthy diet, but science is continually uncovering specific nutritional components in fruits and revealing specific heath benefits. Here is an overview of some recent research.
Açai is becoming more of a household word, thanks in part to increased media coverage of its antioxidant properties. The fruit has recently shown up in Del Monte SuperFruit™ snacks from Del Monte Foods, San Francisco, Calif. (phone 415-247-3000, www.trysuperfruit.com). Available in 8-oz cups, pear, peach, and mixed fruit chunks are mixed with a blend of fruit juices—including açai, blackberry, pomegranate, orange, mango, and passionfruit.
MonaVie™ from MonaVie LLC, South Jordan, Utah (phone 801-748-3100, www.monavie.com), is another popular blend of açai berry and other nutrient-dense fruits. Jessen et al. (2008) investigated the in vitro and in vivo antioxidant and antiinflammatory properties of MonaVie Active (juice with glucosamine and esterified fatty acids). They showed that the antioxidant-rich juice was able to protect cells from oxidative damage. In addition, a small trial showed an increase in serum antioxidants at 1 hr and 2 hr, as well as inhibition of lipid peroxidation at 2 hr post-consumption.
Chan and Shea (2009) demonstrated that mice receiving the human equivalent of two glasses of apple juice per day for one month produced less beta-amyloid, a protein responsible for small plaque formation in the brains of those with Alzheimer’s disease. Researchers concluded that this provides further evidence linking nutritional and genetic risk factors for age-related neurodegeneration and underscores that dietary supplementation may be useful to augment therapeutic approaches.
Bao et al. (2008) showed that bilberry extract may have health benefits due to its antioxidant activity. Eighteen-hour restraint stress of mice resulted in liver damage, with an increase in plasma alanine aminotransferase (ALT) level. Bilberry extract (containing 42.04% anthocyanins) was orally administered to the restraint mice in the amount of 50, 100, and 200 mg per kg per day for 5 days. Plasma ALT decreased at the 200 mg dose, alleviating stress-induced liver damage. Additional results suggested that bilberry extract played an important role in protecting against resistant-stress-induced liver damage by both scavenging free radicals and inhibiting lipid peroxidation.
Erlund et al. (2008) looked at the effects of berry consumption on platelet function, cholesterol, and blood pressure. Seventy-two middle-aged, unmedicated subjects with cardiovascular risk factors consumed moderate amounts of berry or control products for 8 weeks. The berry group consumed 100 g of bilberries and 50 g of a lingonberry-rich nectar every other day. In addition, they consumed 100 g of purée of black currants or strawberries and a juice of raspberry and chokeberry on the other days. Consumption of berries resulted in favorable changes in platelet function, increased high-density lipoprotein cholesterol, and decreased systolic blood pressure.
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Last year, a research team at the University of Reading and the Peninsula Medical School in the Southwest of England showed that phytochemical-rich foods, such as blueberries, are effective at reversing age-related deficits in memory (U.S. Highbush Blueberry Council, 2008). Researchers supplemented a regular diet fed to rats with blueberries over a 12-week period and found that improvements in spatial working memory tasks emerged within 3 weeks and continued throughout the period of the study. The research team showed that the ability of flavonoids to induce memory improvements are mediated by the activation of signaling proteins via a specific pathway in the hippocampus, the part of the brain that controls learning and memory.
Anthocyanins are believed to be responsible for blueberries’ many reported health benefits, including preventing Alzheimer’s disease, age-related macular degeneration and anti-aging. It has been postulated that at least part of the loss of cognitive function in brain aging may be dependent upon a dysregulation in calcium homeostasis. Joseph et al. (2007) reported that blueberry treatment of aging rats prevented the deleterious effects of amyloid beta and dopamine on calcium regulation.
Although the precise mechanisms by which these plant-derived molecules affect the brain are unknown, information from the U.S. Highbush Blueberry Council, Folsom, Calif., (phone 800-824-6395, www.blueberry.org), says that it is believed that they exert their effects on learning and memory by enhancing existing neuronal (brain cell) connections, improving cellular communications, and stimulating neuronal regeneration. The enhancement of both short-term and long-term memory is controlled at the molecular level in neurons.
Cherries are rich in quercetin, an antioxidant recently shown to help boost immunity and reduce risk for respiratory infections such as cold and flu (Davis et al., 2008). Seymour et al. (2007) showed that cherry-enriched diets in rats lowered total blood cholesterol levels and reduced triglycerides. Another study also showed that rats fed a cherry-enriched diet saw reduced total body weight and a 14% fat reduction, in particular the “belly fat” that is most often associated with heart disease risk, while maintaining lean muscle mass (Seymour et al., 2008). The researchers suggested cherry consumption could have an effect on important fat genes and genetic expression. Cherry-enriched diets in the study also reduced total cholesterol levels by about 11% and reduced two known markers of inflammation (Cherry Marketing Institute, 2008).
Natural coconut water is the water inside a coconut. It is naturally filtered for nine months through the dense fibers of the coconut, creating a nutritious, pure, and refreshing isotonic beverage, according to information from iTi Tropicals, Lawrenceville, N.J. (phone 800-223-5484, www.ititropicals.com). Coconut water is naturally sterile and has five essential electrolytes, more potassium than a banana, no added sugars, no fat, no cholesterol, and no preservatives. It’s naturally inherent and unique combination of nutrients gives it incredible health-promoting properties.
In 1998, The Food and Agricultural Organization stated that coconut water is a “natural isotonic beverage” because it has the same electrolyte balance that people have in their blood (FAO, 1998). According to iTi, coconut water’s properties are now being recognized internationally and it may be marketed in the future as a sports-rehydration drink.
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Already known for its role in preventing urinary tract infections, cranberries have recently shown potential anti-cancer activity. Narayansingh and Hurta (2009) reported that crude extracts from cranberry, as well as one of the fruit’s major flavonoid compounds, quercetin, could decrease the expression of certain inflammatory processes linked to colon cancer. The findings indicated that cranberry and quercetin may reduce the risk of colon cancer, possibly by suppressing inflammatory responses.
Grape seed extract is associated with cardiovascular health benefits. Gao et al. (2009) showed that grape seed extract induced apoptosis in leukemia cells. Apoptosis is a natural method of removing potentially dangerous cells. Jurkat cells were treated with various concentrations of grape seed extract (GSE) for 12 hr and 24 hr and with 50 μg/mL GSE for various time intervals. Parallel studies were done in human leukemia cells. The researchers found GSE to activate a protein called JNK that helps regulate apoptosis. When they exposed the leukemia cells to an agent that inhibits JNK, the grape seed extract effect was cancelled out. They concluded that the results showed that GSE induces apoptosis in Jurkat cells through a process that involves sustained JNK activation.
Chan et al. (2007) showed that chronically constipated adults who ate two kiwis a day for a month enjoyed a 23% reduction in discomfort, reducing the time it took food to make it all the way through the digestive tract. Thirty-three constipated patients and 20 healthy volunteers were recruited for a 4-week treatment of kiwi fruit twice daily. There was also improvement in the scores for bothersomeness of constipation and satisfaction of bowel habit, as well as a decrease in frequency of laxative use.
A recent study from Texas AgriLife Research found that plums matched or exceeded blueberries in antioxidants and phytonutrients associated with disease prevention (Phillips, 2009). They found that one plum contained about the same amount of antioxidants as a handful of blueberries. Researchers also tested the effect of the compounds they found on breast cancer cells. They found that phytonutrients in plums inhibited in vitro breast cancer growth without adversely affecting normal cell growth.
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Recent studies point to pomegranate’s potential roles in prevention of arthritis and cancer. Both benefits are due, in part, to pomegranate’s antioxidants, which Guo et al. (2008) showed have potentially greater antioxidant benefits than apple juice. The subjects (average age 63.5) were randomly divided into two groups and assigned to drink 250 ml daily of either apple or pomegranate juice for 4 weeks. They reported that the plasma antioxidant capacity of the subjects consuming pomegranate juice had increased while the subjects consuming apple juice exhibited negligible changes.
Hong et al. (2009) showed that pomegranate polyphenols suppressed expression of genes linked to prostate cancer in human prostate cancer cells. Shukla et al. (2008) evaluated the efficacy of a standardized preparation of POMx, a highly-concentrated blend of polyphenol antioxidants made from pomegranates from POM Wonderful LLC, Los Angeles, Calif. (310-966-5800, www.pomwonderful.com), on collagen-induced arthritis (CIA) in mice, a widely used animal model of rheumatoid arthritis. Consumption of POMx potently delayed the onset and reduced the incidence of CIA in mice. Severity of arthritis was also significantly lower. Histopathology of the arthritic joints demonstrated reduced joint infiltration by the inflammatory cells, and the destruction of bone and cartilage were alleviated.
Strawberries are rich in flavonoids, important compounds that may improve function of the endothelium—the cells that line the inside of blood vessels through the entire circulatory system.
A recent study from the University of California, Davis, and the Illinois Institute of Technology found that a water-soluble extract of strawberry powder caused aortic vessels in endothelial tissue to relax through endothelial-nitric oxide-dependent pathways (California Strawberry Commission, 2008). The results suggested a beneficial role for strawberries in the management of blood pressure and heart disease risk.
In addition to the heart research, the California Strawberry Commission, Watsonville, Calif., (phone 831-724-1301, www.calstrawberry.com), also reported last year that Yale researchers gave strawberries the highest nutrient-density score, based on findings by the Overall Nutrition Quality Index, a measurement system developed by Yale’s Prevention Research Center and several leading health and nutrition experts (California Strawberry Commission, 2008). The system ranks foods on a numeric scale, and strawberries received 100—the highest score possible.
References for the studies cited in this article are available from the author.
Linda Milo Ohr,