Energy value (calories per serving): Low
Saturated fat: Low Cholesterol: None Carbohydrates: High Fiber: Moderate Sodium: Low
Major vitamin contribution: Vitamin C
Major mineral contribution: Calcium
About the Nutrients in This Food
Blueberries have some protein and a little fat. They have no starch but do contain sugars and dietary fiber—primarily pectin, which dissolves as the fruit matures—and lignin in the seeds. (The difference between blueber- ries and huckleberries is the size of their seeds; blueberries have smaller ones than huckleberries.)
One-half cup fresh blueberries has 1.5 g dietary fiber and 9.5 mg. vitamin C (13 percent of the R DA for a woman, 11 percent of the R DA for a man).
The Most Nutritious Way to Serve This Food
Fresh, raw, or lightly cooked.
Buying This Food
Look for: Plump, firm dark-blue berries. The whitish color on the ber- ries is a natural protective coating.
Avoid: Baskets of berries with juice stains or liquid leaking out of the berries. The stains and leaks are signs that there are crushed (and possibly moldy) berries inside.
Storing This Food
Cover berries and refrigerate them. Then use them in a day or two.
Do not wash berries before storing. The moisture increases the chance that they will mold in the refrigerator. Also, handling the berries can damage them, tearing cells and releas- ing enzymes that will destroy vitamins.
Do not store blueberries in metal containers. The anthocyanin pigments in the berries can combine with metal ions to form dark, unattractive pigment/metal compounds that stain the containers and the berries.
Preparing This Food
R inse the berries under cool running water, then drain them and pick them over carefully to remove all stems, leaves, and hard (immature) or soft (over-ripe) berries.
What Happens When You Cook This Food
Cooking destroys some of the vitamin C in fresh blueberries and lets water-soluble B vitamins leach out. Cooked berries are likely to be mushy because heat dissolves the pectin inside.
Blueberries may also change color when cooked. The berries are colored with blue anthocyanin pigments. Ordinarily, anthocyanin-pigmented fruits and vegetables turn red- dish in acids (lemon juice, vinegar) and deeper blue in bases (baking soda). But blueberries also contain yellow pigments (anthoxanthins). In a basic (alkaline) environments, as in a batter with too much baking soda, the yellow and blue pigments will combine, turning the blueberries greenish blue. Adding lemon juice to a blueberry pie stabilizes these pigments; it is a practical way to keep the berries a deep, dark reddish blue.
How Other Kinds of Processing Affect This Food
Canning and freezing. The intense heat used in canning the fruit or in blanching it before freezing reduces the vitamin C content of blueberries by half.
Medical Uses and/or Benefits
Anticancer activity. According to the U.S. Department of Agriculture, wild blueberries rank first among all fruits in antioxidant content; cultivated blueberries (the ones sold in most food markets) rank second. Antioxidants are natural chemicals that inactivate free radicals,
molecule fragments that can link together to form cancer-causing compounds. Several ani- mal studies attest to the ability of blueberries to inhibit the growth of specific cancers. For example, in 2005, scientists at the University of Georgia reported in the journal Food Research International that blueberry extracts inhibited the growth of liver cancer cells in laboratory settings. The following year, researchers at Rutgers University (in New Jersey) delivered data to the national meeting of the American Chemical Society from a study in which laboratory rats fed a diet supplemented with pterostilbene, another compound extracted from blueber- ries, had 57 percent fewer precancerous lesions in the colon than rats whose diet did not contain the supplement. The findings, however, have not been confirmed in humans.
Enhanced memory function. In 2008, British researchers at the schools of Food Biosciences and Psychology at the University of Reading and the Institute of Biomedical and Clinical Sciences at the Peninsula Medical School (England) reported that adding blueberries to one’s normal diet appears to improve both long-term and short-term memory, perhaps because anthocyanins and flavonoids (water-soluble pigments in the berries) activate signals in the hippocampus, a part of the brain that controls learning and memory. If confirmed, the data would support the role played by diet in maintaining memory and brain function.
Urinary antiseptic. A 1991 study at the Weizmann Institute of Science (Israel) suggests that blueberries, like cr anber r ies, contain a compound that inhibits the ability of Escherichia coli, a bacteria commonly linked to urinary infections, to stick to the wall of the bladder. If it cannot cling to cell walls, the bacteria will not cause an infection. This discovery lends some support to folk medicine, but how the berries work, how well they work, or in what “dos- ages” remains to be proven.
Adverse Effects Associated with This Food
Allergic reaction. Hives and angiodemea (swelling of the face, lips, and eyes) are common allergic responses to berries, virtually all of which have been reported to trigger these reac- tions. According to the Merck Manual, berries are one of the 12 foods most likely to trigger classic food allergy symptoms. The others are chocolate, corn, eggs, fish, legumes (peas, lima beans, peanuts, soybeans), milk, nuts, peaches, pork, shellfish, and wheat (see wheat cer ea ls).