CONCERNING the preparation and ingestion of food, I have evolved a simple but, I believe, effective set of rules. Here are six of them:

* No matter what you may have heard, food is neither medicine nor poison. It's the stuff that makes your legs move when you walk.

* If it's advertised on television, it isn't food. It is a harmless digestible whatsis. If the kids press you to buy a TV product, tell them it's made out of liver and petroleum. You may not be far wrong.

* There is only one known way of rendering pot roast fit for human consumption: sauerbraten. If God had intended man to eat unsmoked fish, God would have made man a shark.

* Any cookbook containing the word "crispy" is probably part of a KGB disinformation campaign. There is no such word as "crispy."

* When in doubt on a question of food preparation, ask your grandma, but only if your grandma was born before 1930.

* If you put it in your mouth and it tastes really, really good, it's food.

There, I fancy I've given you something to think about, and I can scarcely wait to plunge into next week's mailbag. For some reason, much of the nation appears to have gone slightly wacky on the subject of vittles. Dark conspiracies are detected on the side panels of cereal boxes, assassins are said to lurk in the sugar bowl, and it is a restful morning when the public fails to rise and discover, in Russell Baker's memorable phrase, that someone thinks lettuce and shaving cause cancer. At the bottom of it all appears to be a deep suspicion of food in all but its most monotonous forms, an even deeper (and entirely irrelevant) suspicion of science, and a hearty leavening of the sort of magical thinking that gave the world Southern California.

A Gordian knot of confusion has resulted, which I now propose to slash with a single stroke of Occam's razor. To wit: the sole object of food preparation is to provide the audience with a toothsome, nutritious feed that satisfies the soul while keeping the anatomy humming. The main problem with canned ravioli and its packaged kindred is not that they contain chemicals, but that they taste funny. And that, of course, is hardly the object of food.

By way of further clearing the air on the perturbed subject, I recommend that the troubled reader run, not walk, to the nearest bookstore and obtain a pair of wonderfully air-clearing volumes, Dear Dr. Stare: What Should I Eat? by Dr. Frederick J. Stare, the founder of Harvard's Department of Nutrition, and his associate, Virginia Aronson (George F. Stickley Co./Scribner's, $14.50), and A Doctor's Guide to Feeding Your Child, by Dr. Stephen J. Atwood (Macmillan, $12.95). Reduced, as it were, to a demi-glace, the sum of their wisdom is this: if you don't eat a balanced diet, you will get sick. The food won't have done it to you, you'll have done it to yourself. For example, if you light out for the tall lettuce of a strict vegetarian diet, you'd better fill up your canteen with some Vitamin B-12, because you're going to need it. A pure macrobiotic diet can kill you, which I suppose is okay if death is your idea of higher spirituality, but it can also kill your kids, which is not okay. If you're too fat, eat less. If you're too thin, eat more. Just remember to keep the old meals balanced, and for pity's sake keep calm; if you don't ingest your recommended daily allowance of zinc today, you'll make it up tomorrow. The body takes care of these things.

While Dr. Atwood adopts the avuncular, rambling style suitable to his profession, stressing the amazing properties of mother's milk while reassuring the nervous bottle-feeder, Stare and Aronson's tone is rather different. Indeed, they often sound rather like someone attempting to explain the periodic table to Carlos Casteneda, which is understandable when you consider that Dr. Stare has actually gone on television and attempted, with spectacular unsuccess, to talk sense to Judy Mazel of Beverly Hills Diet fame, who believes that potatoes ferment into vodka when placed in the human stomach. Accordingly, when they proceed to assert (with excellent reason) that: additives don't hurt you; charcoal doesn't cause cancer; sugar isn't a poison; there is no difference between natural and synthetic vitamins except that natural vitamins cost more, and eggs are good for you, I fear that their attitude of patient exasperation will do little to calm the hysterical. Nerves are rattled out there, fairly twanging like bowstrings beneath the chipper prose of (to take just one example) The Food Sleuth Handbook by Sandra K. Friday and Heidi S. Hurwitz (Atheneum, $15.95).

Friday and Hurwitz are typical of a trend that, if carried to its logical conclusion, will shortly have Americans quarrying their own gallstones. In short, they are self-taught nutritionists who, in the teeth of the evidence (i.e. that national sugar consumption hasn't increased in decades, whereas life expectancy has) give the appearance of believing that the country's diet is fabricated by Lucrezia Borgia rather than Fannie Farmer. They have accordingly devoted a simply enormous amount of time and Yankee ingenuity to the reduction of the usual fats, sugar, salt, and bleached flour in their families' diet, but to what end? To the creation of such feasts as "Hamburger Skillet Supper" and "Macaroni and Cheese Pronto," that's what. Terrific.

Interestingly, it is possible to please both Dr. Stare and the Food Sleuths (well, sort of) by adopting the simple expedient of shopping for fresh ingredients and obeying the seasonal clock, which is what everybody's grandma used to do as a matter of course. It was Mom who went big for frozen meals that are salted down like chipmunk hides, thereby triggering Newton's First Law and creating a hole in the market for such books as Joan Bingham and Dolores Riccio's Smart Shopper's Guide to Food Buying and Preparation (Scribner's, $14.95) and Frieda Arkin's More Kitchen Wisdom (Holt Rinehart and Winston, $13.50). The former tells you how to shop and fill the larder, performing such basic tasks as trimming meat and putting up seasonal fruits. The latter tells you how to potter around the kitchen. This is lore that everybody once knew, the way they knew their own names, but then everybody forgot -- a lacuna in our essential knowledge that has much to do, I suspect, with the culinary manias of the last decade. Ever here, the authors sometimes feel obliged to trim their sails, and there are some curious blind spots -- Bingham and Riccio's obligatory but unnecessary nod in the direction of the health movement, Arkin's strange puzzlement over why cooked pasta should be rinsed, that sort of thing. It would seem that lost lore is not easily regained -- or justified.

Which brings me to a selective sample of recent cookbooks. As a lifelong devotee of good fressing, I have come to regard cookbooks as escape reading of a high order, right up there with a corking murder mystery. Under normal circumstances, I would say that the world has been waiting for Arlene, Heidi and Sandee Eisenberg's Special Guest Cookbook (Beaufort, to be published in October) with its invaluable hints on how to acommodate the kosher guest, and the guest who must watch his cholesterol, his sugar, his salt or his ulcer. So far, so good, but should I really be expected to cook anything, anything at all, for the Pritikin fanatic, the natural food nut, the anorexic, or the general run of ovo-lacto vegetarian? In my experience, all too many of these types hate food, suffer from poor health, propose to live forever, and can't stop talking about all of the foregoing, as though the subject made them at least as interesting as the late Romain Gary. If I have to choose my tabletalk, I prefer to listen to my brother explain how the president's economic plan is going to start working any day now. If these people want to eat a Hunza diet, I sandy let them do it in Hunza.

Almost as annoying are cookbooks that tell you how to make something quick. The desire for swift cooking is another hangover from the era of convenience foods, and unless you're whipping up a croque monsieur or a green salad with vinagrette, there ain't any such thing. Still, sandwich-making, like lemonade construction, appears to be something of a lost art (hint: take two slices of bread and somthing good. Put the bread on the outside of the good stuff, and then put yourself on the outside of the bread), and those in need might want to turn to Diane Harris' The Woman's Day Book of Great Sandwiches (Holt Rinehart and Winston, $16.95; paperback, $9.95) for a few helpful pointers. The same cannot be said for Barbara Gibbons' Salads for All Seasons (Macmillan, $13.95) which contains too much tea shoppe fare of the pineapple and tunafish variety, or Michele Evans' Fearless Cooking Against the Clock (Simon & Schuster, $17.50) which assumes that you have already sliced and grated and otherwise prepared your ingredients (in your sleep, maybe) and evidently hopes to achieve speed by leaving out essential ingredients, such as the nutmeg in the basic cream-and-onion sauce and the vital tobasco-and-butter wash on the Buffalo chicken wings.

As for the last two books on our plate, Martha Rose Shulman's Fast Vegetarian Feasts (Dial, paperback, $11.95) and Tell Erhardt's Chef Tell's Quick Cuisine (written with Rosalyn T. Badalamenti; Warner, $14.95), the titles are a snare and a delusion. Shulman's vegetarian recipes are bright and good even if she does preach too much and use too much salt, but no meal that requires brown rice (cooking time: 40 minutes) can be described as speedy. The fastest thing about Chef Tell's book is the brevity of his recipes, which are fairly whirlwind and definitely not for the recent traveler from the land of frozen asparagus. He has a deft hand with such classical reduced sauces as espagnol and chausseur, but reduced sauces take hours and hours to make. And while he definitely knows his way around the world of good eating, I fear I must seriously question the judgment of a man who proposes to make sauerbraten (preparation time: four days) without gingersnaps. As always, the test is in the eating, and the hell with philosophy.