THE BEST-SELLER lists are not likely to reflect the enthusiasm that is sure to greet "Agriculture Handbook No. 8, Composition of Foods," bible of the American nutritionist, when the extensively revised version of this old standby becomes available.

As chemists at the Nutrient Composition Lab in USDA's Beltsville Agricultural Research Center learn more about food, nutritionists wait for those findings. That's where the Nutrient Data Research Branch of the USDA's Human Nutrition Information Service in Hyattsville comes in. It publishes "Handbook No. 8," which is going to the presses in sections, due for completion in 1985.

The history of "Handbook No. 8" shows some interesting trends in American food tastes and knowledge. And of great interest to nutritionists is the scientific data that tells them whether they should serve fast-food hamburgers or tofu and brown rice. They can't test their foods with a chemist's spectrophotometer or chromatograph, so they go to the book.

"Those guys at the Nutrient Composition Lab are really going at the basic problems, but in the meantime we have to use what we have," says Frank Hepburn, chief of the Hyattsville office, in discussing the book and its use. "In no way could one lab come up with all the information that people are crying for."

First published in 1950, "Handbook No. 8" contained 751 items and included three minerals--calcium, iron and phosphorus--and five vitamins--A, ascorbic acid, thiamin, riboflavin and niacin. When it was first revised in 1963, it included 2,483 foods, and three additional minerals--sodium, potassium and magnesium, although magnesium was included only as a small appendix in the back.

The latest revision will include an estimated 4,000 to 5,000 foods, almost twice the number of 20 years ago. Furthermore, three more minerals--zinc, copper and manganese, the last in limited form--and five more vitamins--folacin (folic acid), pantothenic acid, B-6, B-12, and tocopherol (Vitamin E) also represented with limited data--will be included in the book. In keeping with the direction of nutritional science, each of the food components, old and new, will be measured in smaller quantities. Some components in the new handbook are measured in units one-thousandth as small--in micrograms, not milligrams--as in 1963. The listing of nutrients found in each food is so much longer in the new handbook that each separate food item receives a full page of coverage rather than a single line.

Hepburn doesn't run an spectrophotometer or a chromatograph, either, but he does depend upon modern technology in the form of a computer to compile his nutritional data base--a new-age word that appears nowhere in the 1963 edition of Handbook No. 8. Instead of the apparently absolute values listed in the earlier edition, the revised book reflects statistical sophistication, listing number of food samples tested, standard deviation error and mean nutritional results from the survey.

Variations in geographical origin of food have been factored into the equations as well. For instance, California and Florida avocados are listed separately, showing (among other things) that Florida avocados are lower in calories, protein, fat and mineral content than their California cousins. But for those who don't know the difference between the two avocados, there is also a general avocado listing. It averages the nutritional characteristics of each variety by giving proportionate value to their market shares.

"People don't eat nutrients; they eat food," says Hepburn, and "Handbook No. 8" helps nutritionists translate nutrient value into food terms.