Blueberries
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 the fruits of a shrub that belong to the heath family, which includes the cranberry and bilberry as well as the azalea, mountain laurel and rhododendron. Blueberries grow in clusters and range in size from that of a small pea to a marble. They are deep in color, ranging from blue to maroon to purple-black, and feature a white-gray waxy "bloom" that covers the surface serving as a protective coat. The skin surrounds a semi-transparent flesh that encases tiny seeds.
- Health Benefits
- Description
- History
- How to Select and Store
- How to Enjoy
- Safety
- Nutritional Profile
- References
Blueberries are literally bursting with nutrients and flavor, yet very low in calories. Recently, researchers at Tufts University analyzed 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 neutralize 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 stabilize 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. Cardioprotective Action
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. 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.Protection against Macular Degeneration
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. 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.
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 the fruits of a shrub that belong to the heath (Ericaceae) family whose other members include the cranberry and bilberry as well as the azalea, mountain laurel and rhododendron. Blueberries grow in clusters and range in size from that of a small pea to a marble. They are deep in color, ranging from blue to maroon to purple-black, and feature a white-gray waxy "bloom" that covers the berry's surface and serves as a protective coat. The skin surrounds a semi-transparent flesh that encases tiny seeds. Cultivated blueberries are typically mildly sweet, while those that grow wild have a more tart and tangy flavor.
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.
While blueberries played an important role in North American Indian food culture, being an ingredient in pemmican, a traditional dish composed of the fruit and dried meat, they were not consumed in great amounts by the colonists until the mid-19th century. This seems to be related to the fact that people did not appreciate their tart flavor, and only when sugar became more widely available as a sweetener at this time, did they become more popular.
Blueberries were not cultivated until the beginning of the 20th century, becoming commercially available in 1916. Cultivation of blueberries was spearheaded by a botanist at the United States Department of Agriculture who pioneered research into blueberry production. His work was forwarded by Elizabeth White, whose family established the first commercial blueberry fields.
Choose blueberries that are firm and have a lively, uniform hue colored with a whitish bloom. Shake the container, noticing whether the berries have the tendency to move freely; if they do not, this may indicate that they are soft and damaged or moldy. Avoid berries that appear dull in color or are soft and watery in texture. They should be free from moisture since the presence of water will cause the berries to decay. When purchasing frozen berries, shake the bag gently to ensure that the berries move freely and are not clumped together, which may suggest that they have been thawed and refrozen. Blueberries that are cultivated in the United States are available from May through October while imported berries may be found at other times of the year.
Ripe blueberries should be stored in a covered container in the refrigerator where they will keep for about a week, although they will be freshest if consumed within a few days. Always check berries before storing and remove any damaged berries to prevent the spread of mold. But don't wash berries until right before eating as washing will remove the bloom that protects the berries' skins from degradation. If kept out at room temperature for more than a day, the berries may spoil.
Ripe berries can also be frozen, although this will slightly change their texture and flavor. Before freezing, wash, drain and remove any damaged berries. To better ensure uniform texture upon thawing, spread the berries out on a cookie sheet or baking pan, place in the freezer until frozen, then put the berries in a plastic bag for storage in the freezer. Berries should last up to a year in the freezer. Baby foods containing berries are bereft of anthocyanins, the water-soluble plant pigments responsible not only for the blue, purple, and red color of berries, but also for many of their health benefits. Anthocyanins are found in fresh and frozen berries, but not in processed foods. A study published in the Journal of Agricultural and Food Chemistry found anthocyanins were almost undetectable in canned foods, bread, cereals, and baby foods containing berries, even in baby foods prepared from fruits high in anthocyanins, such as blueberries. This may be due to anthocyanins' unique chemical structure, which renders them unstable even at a neutral pH and therefore much more susceptible to destruction during processing than other phytonutrients, such as proanthocyanidins. To give your children the full health benefits of berries, purchase fresh or frozen berries and purée them.
For some of our favorite recipes, click Recipes.
Tips for preparing blueberries:
Fresh berries are very fragile and should be washed briefly and carefully and then gently patted dry if they are not organic. Wash berries just prior to use to not prematurely remove the protective bloom that resides on the skin's surface. If you know the source of either wild or organic berries try not to wash them at all.
When using frozen berries in recipes that do not require cooking, thaw well and drain prior to using. For cooked recipes, use unthawed berries since this will ensure maximum flavor. Extend the cooking time a few minutes to accommodate for the frozen berries. You may notice that berries used in baked products may take on a green color. This is a natural reaction of their anthocyanidin pigments and does not make the food item unsafe to eat.
A few quick serving ideas:
Add frozen blueberries to your breakfast shake. If the blender container is plastic, allow berries a few minutes to soften, so they will not damage the blender.
Fresh or dried blueberries add a colorful punch to cold breakfast cereals.
For a deliciously elegant dessert, layer yogurt and blueberries in wine glasses and top with crystallized ginger.
Blueberry pie, cobbler and muffins are classic favorites that can be enjoyed throughout the year.
Blueberries and Oxalates
Blueberries are among a small number of foods that contain measurable amounts of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating blueberries. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peer-reviewed research study we've seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalate-containing foods to contribute calcium to the meal plan. If your digestive tract is healthy, and you do a good job of chewing and relaxing while you enjoy your meals, you will get significant benefits —including absorption of calcium—from calcium-rich foods plant foods that also contain oxalic acid. Ordinarily, a healthcare practitioner would not discourage a person focused on ensuring that they are meeting their calcium requirements from eating these nutrient-rich foods because of their oxalate content. For more on this subject, please see "Can you tell me what oxalates are and in which foods they can be found?"
Blueberries are phytonutrient superstars. These fruits contain significant amounts of anthocyanadins, antioxidant compounds that give blue, purple and red colors to fruits and vegetables. In addition, blueberries also contain ellagic acid, another phytochemical that has been shown to prevent cell damage.
Blueberries are a very good source of vitamin C, manganese, and both soluble and insoluble fiber like pectin. Blueberries are also a good source of vitamin E.
For an in-depth nutritional profile click here: Blueberries.
In-Depth Nutritional Profile
In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Blueberries is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.Introduction to Food Rating System Chart
The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that that amount represents; the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on our Food and Recipe Rating System.
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