The move to get more restaurateurs on the nutrition bandwagon has become official with the National Restaurant Association's new guide, appropriately called "A Nutrition Guide for the Restaurateur."

The guide, written by NRA nutritionist Claire Regan, includes basic nutrition information, content counts for fat, cholesterol, sodium, calories and fiber in various foods, preparation tips and substitutions. Included in the book are ideas for increasing fiber content on a menu, the caloric value of the high-fat cottage cheese and hamburger "diet plate" and an example of survey questions restaurateurs could ask customers to assess their interest in nutrition.

Regan said the impetus for the guide came from a lack of publications geared to food-service establishments that she could recommend to restaurateurs asking for help in developing nutritious menus. The 72-page guide is $15 for members, $30 for nonmembers. Call the NRA publications department at 638-6100 for ordering information. Sodium Labeling Arrives

On Tuesday, the Food and Drug Administration's sodium labeling regulation goes into effect. Be aware that the regulation does not require that all packaged foods list sodium content -- only those that already include nutrition labeling. (Currently, about 55 percent of the foods regulated by the FDA bear nutrition labels.) The regulation also gives manufacturers who do not list any nutrition information the option of listing sodium content alone.

Companies may also use the following definitions to describe the sodium content of their foods. (As a benchmark, the National Academy of Sciences has recommended that Americans consume between 1,100 and 3,300 milligrams of sodium a day, or between 1 1/2 and 4 teaspoons of salt):

Sodium free: less than 5 milligrams of sodium in a serving.

Very low sodium: 35 milligrams or less in a serving.

Low sodium: 140 milligrams or less per serving.

Reduced sodium: if the usual level of sodium has been reduced by at least 75 percent.