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r BananasNutritional ProfileEnergy value (calories per serving): Moderate

Protein: Low

Fat: Low

Saturated fat: Low

Cholesterol: None

Carbohydrates: High

Fiber: Moderate

Sodium: Low

Major vitamin contribution: B vitamins, vitamin C

Major mineral contribution: Potassium, magnesium

About the Nutrients in This FoodA banana begins life with more starch than sugar, but as the fruit ripens its starches turn to sugar, which is why ripe bananas taste so much better than unripe ones.* The color of a banana’s skin is a fair guide to its starch/sugar ratio. When the skin is yellow-green, 40 percent of its carbohydrates are starch; when the skin is fully yellow and the banana is ripe, only 8 per-cent of the carbohydrates are still starch. The rest (91 percent) have broken down into sugars—glucose, fructose, sucrose, the most plentiful sugar in the fruit. Its high sugar content makes the banana, in its self-contained packet, a handy energy source.

Bananas are a high-fiber food with insoluble cellulose and lignin in the tiny seeds and soluble pectins in the flesh. They are also a good source of vitamin C and potassium.

One small (six-inch) banana or a half-cup of sliced banana has 2.6 g dietary fiber and 8.8 mg vitamin C (12 percent of the RDA for a woman, 10 percent of the RDA for a man), plus 363 mg potassium.

The Most Nutritious Way to Serve This FoodFresh and ripe. Green bananas contain antinutrients, proteins that inhibit the actions of amylase, an enzyme that makes it possible for us to digest

* They are also more healthful. Green bananas contain proteins that inhibit amy-lase, an enzyme that makes it possible for us to digest complex carbohydrates.

starch and other complex carbohydrates. Raw bananas are richer in potassium than cooked bananas; heating depletes potassium.

Diets That May Restrict or Exclude This Food* * *

Buying This FoodLook for: Bananas that will be good when you plan to eat them. Bananas with brown specks on the skin are ripe enough to eat immediately. Bananas with creamy yellow skin will be ready in a day or two. Bananas with mostly yellow skin and a touch of green at either end can be ripened at home and used in two or three days.

Avoid: Overripe bananas whose skin has turned brown or split open. A grayish yellow skin means that the fruit has been damaged by cold storage. Bananas with soft spots under the skin may be rotten.

Storing This FoodStore bananas that aren’t fully ripe at room temperature for a day or two. Like avocados, bananas are picked green, shipped hard to protect them from damage en route and then sprayed with ethylene gas to ripen them quickly. Untreated bananas release ethylene natu-rally to ripen the fruit and turn its starches to sugar, but natural ripening takes time. Artificial ripening happens so quickly that there is no time for the starches to turn into sugar. The bananas look ripe but they may taste bland and starchy. A few days at room temperature will give the starches a chance to change into sugars.

Store ripe bananas in the refrigerator. The cold air will slow (but not stop) the natural enzyme action that ripens and eventually rots the fruit if you leave it at room temperature. Cold storage will darken the banana’s skin, since the chill damages cells in the peel and releases polyphenoloxidase, an enzyme that converts phenols in the banana peel to dark brown compounds, but the fruit inside will remain pale and tasty for several days.

Preparing This FoodDo not slice or peel bananas until you are ready to use them. When you cut into the fruit, you tear its cell walls, releasing polyphenoloxidase, an enzyme that hastens the oxidation of phenols in the banana, producing brown pigments that darken the fruit. (Chilling a banana produces the same reaction because the cold damages cells in the banana peel.) You can slow the browning (but not stop it completely) by dipping raw sliced or peeled bananas into a solution of lemon juice or vinegar and water or by mixing the slices with citrus fruits in a fruit salad. Overripe, discolored bananas can be used in baking, where the color doesn’t matter and their intense sweetness is an asset.

Bananas

What Happens When You Cook This FoodWhen bananas are broiled or fried, they are cooked so quickly that there is very little change in color or texture. Even so, they will probably taste sweeter and have a more intense aroma than uncooked bananas. Heat liberates the volatile molecules that make the fruit taste and smell good.

How Other Kinds of Processing Affect This FoodDrying. Drying removes water and concentrates the nutrients and calories in bananas. Bananas may be treated with compounds such as sulfur dioxide to inhibit polyphenoloxi-dase and keep the bananas from browning as they dry. People who are sensitive to sulfites may suffer severe allergic reactions, including anaphylactic shock, if they eat these treated bananas.

Freezing. Fresh bananas freeze well but will brown if you try to thaw them at room tem-perature. To protect the creamy color, thaw frozen bananas in the refrigerator and use as quickly as possible.

Medical Uses and/or BenefitsLower risk of stroke. Various nutrition studies have attested to the power of adequate potassium to keep blood pressure within safe levels. For example, in the 1990s, data from the long-running Harvard School of Public Health/Health Professionals Follow-Up Study of male doctors showed that a diet rich in high-potassium foods such as bananas, oranges, and plantain may reduce the risk of stroke. In the study, the men who ate the higher number of potassium-rich foods (an average of nine servings a day) had a risk of stroke 38 percent lower than that of men who consumed fewer than four servings a day. In 2008, a similar survey at the Queen’s Medical Center (Honolulu) showed a similar protective effect among men and women using diuretic drugs (medicines that increase urination and thus the loss of potassium).

Improved mood. Bananas and plantains are both rich in serotonin, dopamine, and other natural mood-elevating neurotransmitters—natural chemicals that facilitate the transmis-sion of impulses along nerve cells.

Potassium benefits. Because potassium is excreted in urine, potassium-rich foods are often recommended for people taking diuretics. In addition, a diet rich in potassium (from food) is associated with a lower risk of stroke. A 1998 Harvard School of Public Health analysis of data from the long-running Health Professionals Study shows 38 percent fewer strokes among men who ate nine servings of high potassium foods a day vs. those who ate less than four servings. Among men with high blood pressure, taking a daily 1,000 mg potas-sium supplement—about the amount of potassium in one banana—reduced the incidence of stroke by 60 percent.

Adverse Effects Associated with This FoodDigestive Problems. Unripe bananas contain proteins that inhibit the actions of amylase, an enzyme required to digest starch and other complex carbohydrates.

Sulfite allergies. See How other kinds of processing affect this food.

Latex-fruit syndrome. Latex is a milky fluid obtained from the rubber tree and used to make medical and surgical products such as condoms and protective latex gloves, as well as rub-ber bands, balloons, and toys; elastic used in clothing; pacifiers and baby bottle-nipples; chewing gum; and various adhesives. Some of the proteins in latex are allergenic, known to cause reactions ranging from mild to potentially life-threatening. Some of the proteins found naturally in latex also occur naturally in foods from plants such as avocados, bananas, chestnuts, kiwi fruit, tomatoes, and food and diet sodas sweetened with aspartame. Persons sensitive to these foods are likely to be sensitive to latex as well. NOTE: The National Insti-tute of Health Sciences, in Japan, also lists the following foods as suspect: Almonds, apples, apricots, bamboo shoots, bell peppers, buckwheat, cantaloupe, carrots, celery, cherries, chestnuts, coconut, figs, grapefruit, lettuce, loquat, mangoes, mushrooms, mustard, nectar-ines, oranges, passion fruit, papaya, peaches, peanuts, peppermint, pineapples, potatoes, soybeans, strawberries, walnuts, and watermelon.

Food/Drug InteractionsMonoamine oxidase (MAO) inhibitors. Monoamine oxidase inhibitors are drugs used to treat depression. They inactivate naturally occurring enzymes in your body that metabolize tyra-mine, a substance found in many fermented or aged foods. Tyramine constricts blood vessels and increases blood pressure. If you eat a food containing tyramine while you are taking an MAO inhibitor, you cannot effectively eliminate the tyramine from your body. The result may be a hypertensive crisis. There have been some reports in the past of such reactions in people who have eaten rotten bananas or bananas stewed with the peel.

False-positive test for tumors. Carcinoid tumors—which may arise from tissues of the endo-crine system, the intestines, or the lungs—secrete serotonin, a natural chemical that makes blood vessels expand or contract. Because serotonin is excreted in urine, these tumors are diagnosed by measuring the levels of serotonin by-products in the urine. Bananas contain large amounts of serotonin; eating them in the three days before a test for an endocrine tumor might produce a false-positive result, suggesting that you have the tumor when in fact you don’t. (Other foods high in serotonin are avocados, eggplant, pineapple, plums, tomatoes, and walnuts.)

Bananas