Any of various dry fruits that generally consist of an edible kernel enclosed in a shell that can range from medium-hard, thin and brittle to woody and tough. Botanically speaking, some foods we know as nuts are actually seeds or legumes. Among the more popular of the other "nuts" are almonds, cashews, pine nuts, etc. Most nuts are sold both shelled and unshelled. Shelled nuts come in many forms including blanched or not, whole, halved, chopped, sliced or minced. Additionally, shelled nuts come raw, dry-roasted, oil-roasted, with or without salt, smoked, candied and with various flavorings such as jalapeño and garlic. They're sold in plastic bags and boxes, and vacuum-packed in cans and jars. When buying unshelled nuts in bulk, choose those that are heavy for their size, with solid shells sans cracks or holes. The nut's kernel should not be loose enough to rattle when shaken. Shelled nuts should be plump, crisp and uniform in color and size. In general, nuts should be purchased as fresh as possible. Rancid nutmeats will ruin whatever food they flavor. To be sure that nuts are fresh — whether shelled or unshelled — buy them from a supplier with rapid turnover. Because of their high fat content, rancidity is always a hazard with nuts. For that reason they should be stored airtight in a cool place. Shelled nuts can be refrigerated in this manner up to 4 months, frozen up to 6 months. As a general rule (and depending on their freshness at the time of storage), unshelled nuts will keep about twice as long as shelled. Popular nut by-products include meal or flour (usually found in health-food stores) and nut butter and oils (the most popular being almond, hazelnut, peanut and walnut oils). Nuts are high in calcium, folic acid, magnesium, potassium, vitamin E and fiber. Some scientific studies have concluded that a daily portion of just 1 ounce of nuts rich in monounsaturated fat can reduce the risk of heart disease by up to 10 percent. The nuts highest in monounsaturated fat are almonds, Brazil nuts, hazelnuts, macadamia nuts, pecans, pistachios and walnuts. And, although 1 ounce of nuts delivers about 180 calories and 17 fat grams, 50 to 80 percent of that fat is monounsaturated (the "good" fat that helps reduce the level of LDL — the "bad" cholesterol). Nuts are wonderful simply eaten out of hand as well as used in a wide variety of sweet and savory dishes for meals from breakfast to dinner. The flavor of most nuts benefits from a light toasting, either on stovetop or in the oven.