Nutrition in a nutshell.

NUTRITION in a NUTSHELL

If sometimes you feel like a nut, you're not alone. Americans are nuts about nuts. Each year, in fact, we spend more than $2 billion on them. Once a food staple in ancient culture, nuts - the shell-encased fruits of nonleguminous trees - have resurged as an important ingredient in our daily diets.

With more than a dozen different kinds of nuts to choose from, it's hard not to love at least one. The best-seller among nuts is the peanut, which is really not a nut at all. Also called "gobbers" or "ground nuts," peanuts are actually in the legume family along with beans, peas, and lentils. But we think of them as nuts because of their similar appearance and nutrient content.

Also, some of the other foods we call nuts, such as Brazil nuts and cashews, are really the seeds of fruits. And the coconut is a drupe - a fruit with a hard kernel, like the cherry or plum.

Any way you look at it, the collection of edibles we refer to as nuts is enjoying a renaissance. No longer relegated to nibbles at parties or ball games, the humble nut is in vogue.

From a nutritional standpoint, this is good news. Nuts are a powerhouse of protein, ranging from 10 percent to 25 percent by weight. One of the best vegetable sources of protein around, nuts have an excellent balance of amino acids. When you combine them with other protein-containing plant foods, the result is a complete protein comparable to what's found in meat.

But not all nuts are created equal in the protein department. Some are better sources than others. When you look at the accompanying chart you can see that peanuts pack the most protein (more than 7 grams per ounce); pine nuts, almonds, and pistachio nuts fall in close behind. Chestnuts, coconut, and macadamia nuts are fairly low in protein (ranging from 0.9 to 2.1 grams per ounce).

Nuts also differ in the amount of fat they contain. Overall, nuts are rather high in fat. But fortunately the fats are mostly unsaturated fats - either polyunsaturates or monounsaturates, which help to lower blood cholesterol levels. The one big exception to this rule is the coconut. Coconuts contain primarily saturated fat, which raises blood cholesterol and is linked to an increased risk of heart disease.

If you're looking to cut fat, the dryroasted nuts tend to have a bit less fat than the oil-roasted varieties. You can also look for "natural" or "old-fashioned" nut butters, which are 100 percent nuts with no added oil. Or you can make your own nut butters by grinding nuts in your blender or food processor.

Such butters also avoid the problem of hydrogenation. This process is involved in most commercially produced peanut butter. The purpose is to make the oil stay fresh longer and prevent it from separating out. But another result is that it converts unsaturated fats to a more saturated (thus less desirable) form.

Besides protein, nuts are good sources of bulk-producing fiber, especially when eaten with their skins or hulls. They're also fairly rich in potassium, an often-missed nutrient among dieting women and the elderly. Two other minerals abundant in nuts are zinc and copper; these two commonly overlooked minerals may be in short supply in many diets, according to recent food consumption data. Zinc assists the immune system, while copper is needed for healthy blood.

Most nuts also provide a bounty of the B vitamins: thiamin, riboflavin, and niacin. In fact, peanut butter is a better source of niacin than most meats. You'll also pick up some magnesium, calcium, phosphorus, and vitamin E by eating nuts.

If you choose them carefully, nuts won't add much sodium to your diet. They're naturally low in sodium, but this nutritional advantage is often eradicated by the salting done in processing. You can look for unsalted nuts and unsalted nuts spreads if you're keeping an eye on the sodium you consume.

Another plus you'll get with nuts is their "anticariogenicity." This simply means they don't cause cavities. Nuts are much kinder to teeth than most commonly eaten snacks.

And despite their calorie content, nuts compare quite well when measured against other popular nibble foods. For the calories you consume, you get much more back in the form of protein and other nutrients than if you grabbed a bag of chips or pretzels.

When it comes to snacks, the American public frequently turns to nuts. In fact, we continue to eat more and more nuts every year, with the peanut far and away the favorite. Americans eat five times more peanuts than any tree nut, with about 52 percent in the form of peanut butter.

Compared to other nuts, peanuts stack up quite well. They pack in the most protein and contain more monounsaturates than other nuts. Monounsaturated fat is currently recognized as the most heart-healthy choice. These "good" fats have been shown to bring down blood levels of LDL-cholesterol, the "bad" cholesterol that promotes atherosclerosis. They do that without affecting the "good" HDL cholesterol, the kind that helps protect against heart disease. This is a plus over the polyunsaturates that are predominate in most other nuts. Polyunsaturates reduce both kinds of cholesterol in the blood: the artery-damaging LDL cholesterol and the artery-protecting HDL cholesterol.

The ever-popular peanut butter also stands up well against other sandwich fillers. For example, a sandwich made with two tablespoons of peanut butter provides 20 percent of the recommended daily allowance for protein for an adult. It's also a portable nourishment that needs no refrigeration - an important attribute for brown-bag fare.

Bear in mind that nuts are a concentrated food - a little goes a long way. Don't go overboard and build your whole diet on them.

Now that you're "nut savvy," the familiar expression "nuts to you" to longer needs to be an insulting remark. If it's offered in a nutritional context, it can be taken as a wholesome compliment. Consult the chart for a "nuts-and-bolts" description of these nutritional wonders. And the next time you feel like a nut, you'll know you're making a wise choice.

Janet Helm, M.S., R.D., is an account executive for a public relations firm in New York City.