For RDs, expertise results from a steady diet of work and study

As America's obesity numbers increase, as we're barraged by fads and food scares, and as we have to make sense of the new food pyramid, it seems there's no refuge for confused consumers. That's where registered dietitians come in.

An RD can take the mystery out of instructions for a diabetic, make it easy for a heart patient to follow doctors' orders, and teach people to adjust to new situations, including allergies, menopause, and pregnancies. In some instances, a registered dietitian is the next stop after the doctor's office.

With coursework in biology, anatomy, organic chemistry, microbiology, biochemistry, physiology, statistics, food composition, human metabolism, and medical nutrition therapy, dietitians can make sense of any patient's needs. Nancie Herbold, chairman of the nutrition department at Simmons College, says, ''People don't realize just how much science goes into the training of a dietitian." And while some graduates will work with patients in hospitals or in their own private practices, others will join food service teams, the research and development arm of food corporations, or government-sponsored programs such as Project Head Start.

In the introductory food science lab course run by Simmons' assistant professor Sari Edelstein, students are studying crystallization, or what happens to food when it freezes. They're making chocolate mousse. In lab coats and white caps, the students make a regular mousse with cream, eggs, sugar, and chocolate, another group varies the amount of sugar, another substitutes half-and-half, and a fourth uses egg whites in place of whole eggs. The idea here is to see whether they can modify the dessert so it is healthful but still tastes good.

With blenders whirring and students stirring, multiple versions of mousse are completed, marked, and frozen. Before the mousse is tasted, a frozen dab is set on a slide and studied under a microscope. It is not enough to know how different ingredients affect taste and nutrition, students must know why.

It is this application of science that makes RDs valuable, especially in the face of a public clamoring for the next fad diet. Most RDs shudder at the thought of diets that eliminate entire food groups because they deny the body necessary nutrients. It's this thinking that has given them the reputation as nutrition police, something they're having to overcome by being practical without preaching. Edelstein explains that ultimately, everyone wants good taste. ''Food is a pleasure," she says. ''If we forget that, the public won't listen to us."

The rigorous training includes 900 hours in an internship after graduation. Only then can they sit for a national exam and receive the accreditation to put RD after their name.

Some students come to the study of nutrition to help populations who suffer from opposite ends of the food spectrum. Sareena Rasheed, who comes from India and is preparing for her accreditation exam, is concerned about hunger due to poverty as well as obesity in middle and upper classes in her country. She came to Simmons with a home economics degree from India's University of Kerala and all but had to begin all over again.

Alison Rainey of Newton, a graduate student in nutrition at Framingham State College, had a degree in international studies and had to spend a year and a half taking science courses to catch up. ''Nutrition and healthy eating had always been a part of my life," says Rainey, ''but I didn't realize I could make a career of it."

There are plenty of jobs for registered dietitians, especially when they have combined degrees. Tricia Silverman, who has a private practice in Dedham called NuTricia's Lifestyles, graduated from the State University of New York at Oneonta then earned an MBA at Babson College. ''I am an entrepreneur at heart and this gave me the confidence to start my own business," she says.

But most people encounter dietitians when their health is compromised. This can be difficult. Simmons instructor Janet Washington, who has counseled patients and taught hundreds of students, says, ''I always tell them to build on the positive."

At the Simmons lab, students are tasting the various chocolate mousse recipes and coming to some conclusions. With a Goldilocks-like scene in the room, some are dipping spoons into a too-liquid version and finding they can't keep the mousse on them. They drink it instead. Others who adjusted sugar are puckering their lips: the mousse isn't sweet enough. The group who kept the recipe intact, simply reducing ingredients, pronounced their results healthy and acceptable. That one was just right.