With flavors that range from mildly sweet to tart and tangy, blueberries are nutritional stars bursting with nutrition and flavor while being very low in calories. Blueberries are at their best from May through October when they are in season.
Blueberries are literally bursting with nutrients and flavour, yet very low in calories. Researchers at Tufts University in Boston USA, analysed 60 fruits and vegetables for their antioxidant capability. Blueberries came out on top, rating highest in their capacity to destroy free radicals.
An Antioxidant Powerhouse
Packed with antioxidant phytonutrients called anthocyanidins, blueberries neutralise free radical damage to the collagen matrix of cells and tissues that can lead to cataracts, glaucoma, varicose veins, hemorrhoids, peptic ulcers, heart disease and cancer. Anthocyanins, the blue-red pigments found in blueberries, improve the integrity of support structures in the veins and entire vascular system. Anthocyanins have been shown to enhance the effects of vitamin C, improve capillary integrity, and stabilise the collagen matrix (the ground substance of all body tissues). They work their protective magic by preventing free-radical damage, inhibiting enzymes from cleaving the collagen matrix, and directly cross-linking with collagen fibers to form a more stable collagen matrix.
While wine, particularly red wine, is touted as cardioprotective since it is a good source of antioxidant anthocyanins, a recent study found that blueberries deliver 38% more of these free radical fighters. In this study, published in the Journal of Agriculture and Food Chemistry, researchers found that a moderate drink (about 4 ounces) of white wine contained .47 mmol of free radical absorbing antioxidants, red wine provided 2.04 mmol, and a wine made from highbush blueberries delivered 2.42 mmol of these protective plant compounds.
A Visionary Fruit
Extracts of bilberry (a cousin of blueberry) have been shown in numerous studies to improve nighttime visual acuity and promote quicker adjustment to darkness and faster restoration of visual acuity after exposure to glare. This research was conducted to evaluate claims of bilberry's beneficial effects on night vision made by British Air Force pilots during World War II who regularly consumed bilberry preserves before their night missions.
Protection against Macular Degeneration
Your mother may have told you carrots would keep your eyes bright as a child, but as an adult, it looks like fruit is even more important for keeping your sight. Data reported in a study published in the Archives of Ophthalmology indicates that eating 3 or more servings of fruit per day may lower your risk of age-related macular degeneration (ARMD), the primary cause of vision loss in older adults, by 36%, compared to persons who consume less than 1.5 servings of fruit daily.
In this study, which involved over 110,000 women and men, researchers evaluated the effect of study participants' consumption of fruits; vegetables; the antioxidant vitamins A, C, and E; and carotenoids on the development of early ARMD or neovascular ARMD, a more severe form of the illness associated with vision loss. Food intake information was collected periodically for up to 18 years for women and 12 years for men.
While, surprisingly, intakes of vegetables, antioxidant vitamins and carotenoids were not strongly related to incidence of either form of ARMD, fruit intake was definitely protective against the severe form of this vision-destroying disease. Three servings of fruit may sound like a lot to eat each day, but by simply topping off a cup of yogurt or green salad with a half cup of blueberries, tossing a banana into your morning smoothie or slicing it over your cereal, and snacking on an apple, plum, nectarine or pear, you've reached this goal.
A Better Brain with Blueberries
In laboratory animal studies, researchers have found that blueberries help protect the brain from oxidative stress and may reduce the effects of age-related conditions such as Alzheimer's disease or dementia. Researchers found that diets rich in blueberries significantly improved both the learning capacity and motor skills of aging animals, making them mentally equivalent to much younger ones.
Promotion of Gastrointestinal Health
In addition to their powerful anthocyanins, blueberries contain another antioxidant compound called ellagic acid, which blocks metabolic pathways that can lead to cancer. In a study of over 1,200 elderly people, those who ate the most strawberries (another berry that contains ellagic acid) were three times less likely to develop cancer than those who ate few or no strawberries. In addition to containing ellagic acid, blueberries are high in the soluble fiber pectin, which has been shown to lower cholesterol and to prevent bile acid from being transformed into a potentially cancer-causing form.
Protection against Colon Cancer
Laboratory studies published in the Journal of Agricultural and Food Chemistry show that phenolic compounds in blueberries can inhibit colon cancer cell proliferation and induce apoptosis (programmed cell death).
Extracts were made of the blueberry phenols, which were freeze-dried and further separated into phenolic acids, tannins, flavonols, and anthocyanins. Then the dried extracts and fractions were added to cell cultures containing two colon cancer cell lines, HT-29 and Caco-2.
In concentrations normally found in laboratory animal plasma after eating blueberries, anthyocyanin fractions increased DNA fragmentation (a sign that apoptosis or cell death had been triggered) by 2-7 times. Flavonol and tannin fractions cut cell proliferation in half at concentrations of 70-100 and 50-100 microg/mL, while the phenolic fraction was also effective, but less potent, reducing proliferation by half at concentrations of 1000 microg/mL.
Bottomline: eating blueberries may reduce colon cancer risk.
Protection against Ovarian Cancer
Among their rich supply of phytonutrients, blueberries include a flavonoid called kaempferol. Research calculating flavonoid intake in 66,940 women enrolled in the Nurses Health Study between 1984 and 2002 revealed that women whose diets provided the most kaempferol had a 40% reduction in risk of ovarian cancer, compared to women eating the least kaempferol-rich foods. In addition to blueberries, foods richest in kaempferol include tea (nonherbal), onions, curly kale, leeks, spinach, and broccoli.
A significant 34% reduction in ovarian cancer risk was also seen in women with the highest intake of the flavone luteolin (found in citrus). Int J Cancer. 2007 Apr 30; Am J Clin Nutr. 2004 May;79(5):727-47.
The Healthier Elimination
Blueberries can help relieve both diarrhea and constipation. In addition to soluble and insoluble fiber, blueberries also contain tannins, which act as astringents in the digestive system to reduce inflammation. Blueberries also promote urinary tract health. Blueberries contain the same compounds found in cranberries that help prevent or eliminate urinary tract infections. In order for bacteria to infect, they must first adhere to the mucosal lining of the urethra and bladder. Components found in cranberry and blueberry juice reduce the ability of E. coli, the bacteria that is the most common cause of urinary tract infections, to adhere.
Blueberries are native to North America where they grow throughout the woods and mountainous regions in the United States and Canada. This fruit is rarely found growing in Europe and has only been recently introduced in Australia.
There are approximately 30 different species of blueberries with different ones growing throughout various regions. For example, the Highbush variety can be found throughout the Eastern seaboard from Maine to Florida, the Lowbush variety throughout the Northeast and Eastern Canada, and the Evergreen variety throughout states in the Pacific Northwest.