How to choose nutritious summer fruit

Watermelon

Why: Low in calories, not too expensive and it's 92 percent water — which quenches your thirst and fills you up on a hot summer day.

Health perks: Watermelon has 7.5 to 10 milligrams per cup of the antioxidant lycopene, believed to guard against heart disease and some cancers. That's about 40 percent more than is found in raw tomatoes (cooked tomatoes have more). It's a good source of vitamins A and C, and it also contains potassium, vitamin B6 and thiamin. Plus, it has citrulline, an amino acid that may help reduce the risk of cardiovascular disease, stimulate the immune system and accelerate the healing of wounds.

Nutrition: Serving size: 1 cup, diced (152g), calories 46, total fat 0.2g, cholesterol 0mg, sodium 2mg, total carbohydrate 11.5g, dietary fiber 0.6g, sugars 9.4g, protein 0.9g.

Seek out: Firm, juicy, red flesh without white streaks and a rind free of cracks, bruises or mold. The seeds should be dark brown or black. According to James Parker, associate global produce coordinator for Whole Foods Market, "Look for melons that have a uniform shape. Ripe fruit will have a slight give on the end opposite to the stem and a slight yellowing of the rind on the lightest part of the outside."

Peter Romano, the produce director at New York City's famed Fairway Market, says you can tap the melon in the middle with your palm: If it's ripe, you should hear a hollow sound.

Avoid: Pale flesh, white streaks and whitish seeds. The rind should be free of bruises, soft spots or mold. "And make sure there are no splits, veins, hollow pockets, dark red streaks or blood-red [as opposed to fire-engine-red] color," says Romano.

Storage: According to chef Aliza Green, author of Field Guide to Produce, ripe watermelon will keep best (for about five days) if cut up, covered with plastic wrap and refrigerated.

Peaches

Why: They are sweet and are very low in calories.

Health perks: One peach delivers 10 percent of the daily vitamin C you need and 2 grams of fiber. And peaches have a low glycemic load.

Nutrition: Serving size: one medium (2-2/3 inch diameter), calories 58, total fat 0.4g, total carbohydrate 14.3g, dietary fiber 2.2g, sugars 12.6g, protein 1.4g.

Seek out: According to Green, "Make sure that the stem end is yellow or cream-colored. Also, look for a well-defined crease and a pleasingly sweet fragrance. They should be soft to the touch."

Avoid: "Make sure the peach doesn't have 'green shoulders' around the stem, suggesting premature picking. A deep, red-brown color, softening of the fruit or shriveling of the skin at the stem indicates it's overripe," advises Green. Never squeeze peaches: They bruise.

Storage: Don't store in the refrigerator or in sunlight. One of the better ways to ripen peaches is to place them in a brown paper bag, fold the top and leave them for a day or so.

Cantaloupe

Why: One-quarter of a melon (about 15 cantaloupe balls) has only 70 calories or so.

Health perks: It's low in calories and high in the antioxidant beta carotene, vitamins A and C, and a good source of vitamins B6 and B3 (niacin), folate and potassium.

Nutrition: Serving size: One-quarter of a large melon (about 6 ½ inches in diameter), calories 69, total fat 0.4g, cholesterol 0mg, sodium 33mg, total carbohydrate 16.6g, dietary fiber 1.8g, sugars 16g, protein 1.7g.

Seek out: Fragrant, symmetrical melons, heavy for their size, with a yellow or cream undertone and no bruises. "Another indicator is the stem: If it still has one and it won't come off easily, chances are it's not ready to eat," says Parker. Additionally, the skin color between the netting should be yellowish-buff, yellowish-gray or pale yellow — not green.

Avoid: According to Green, overripe cantaloupes have "lumps or soft spots." She suggests avoiding rock-hard or lopsided melons. Also, watch out for mold, which can indicate decay.

Storage: Uncut melons can be stored at room temperature for up to a week. Refrigerate cut melon in an airtight container for up to five days.

Cherries

Why: Delicious, sweet and oh-so-low in calories.

Health perks: Fifteen cherries have only 64 calories and more than 10 percent of the daily value of vitamin C. They are also rich in vitamin E, contain 2 grams of fiber, and are a good source of potassium, magnesium, iron and folate.

Cherries contain a pigment called anthocyanin (responsible for their color), an antioxidant linked to a variety of health benefits including reduction of risk for heart disease and cancer. Additionally, cherries are one of the few food sources of melatonin, shown to aid in sleep.

Nutrition: Serving size: 15 cherries (102g), calories 64, total fat 0.2g, cholesterol 0mg, sodium 0mg, total carbohydrate 16.3g, dietary fiber 2.1g, sugars 13.1g, protein 1.1g.

Seek out: High-quality cherries are firm and dark red, with bright, lustrous, plump-looking surfaces and fresh-looking stems.

Avoid: Soft, shriveled or blemished cherries. Green also suggests avoiding dark or brittle stems.

Storage: Remove any that are soft or split, says Green. Then refrigerate. Check the fruit occasionally and remove any that have gone bad. You can freeze cherries (with or without pits) by rinsing and draining them thoroughly, spreading them in a single layer on a cookie sheet and placing them in the freezer.

Charles Stuart Platkin is a nutrition and public health advocate and author of "The Diet Detective's Count Down."