We hear that fruits and vegetables are good for what ails you. Nutrients in these foods support health and help protect against heart disease and some forms of cancer, among other benefits. Pile your plate with heaping helpings -- that's the prevailing advice.

Unless, of course, you suffer from fructose intolerance.

People with fructose intolerance, also called fructose malabsorption, have trouble digesting foods that contain fructose, a natural form of sugar found in fruits and vegetables, many sweeteners, and some breads and cereals. Symptoms include gas, bloating, nausea and diarrhea.

One reader was recently diagnosed with a double whammy of lactose intolerance and fructose intolerance. She told me her symptoms resembled those of irritable bowel syndrome. Her doctor ruled out celiac disease.

Poking around on the Web, she learned that some experts think fructose intolerance is underreported and that the prevalence of high fructose corn syrup in processed foods and drinks may contribute to the problem.

"I am so hungry and miss fruits and vegetables so much and the benefits of the fiber!" she wrote. "I would be interested in any suggestions or resources you can recommend."

Unfortunately, the guidance is somewhat murky at this point. In part, that's because the science is not clear about the extent to which fructose in the diet may contribute to gastrointestinal problems, nor how well elimination diets work to relieve the symptoms. In elimination diets, suspect foods are removed for several days up to several weeks to see if symptoms disappear.

One five-year study by researchers at the University of Iowa found that people with carbohydrate intolerances did get some relief when they ate a diet low in fructose.

Pulling that off takes commitment, though.

Large amounts of fructose are found naturally in fruits, fruit juices, honey and maple syrup. Other forms of sugar break down into fructose once they are digested. Sorbitol, a sugar alcohol used in some "sugar-free" products such as hard candies and sugar-free chewing gum, is one example.

Table sugar, or sucrose, is another example. All forms of granulated sugar (white and brown), confectioners' sugar, corn syrup and foods sweetened with these forms of sugar are off limits on a low-fructose diet. That means steering clear of soft drinks, sweet tea, candy, cake, cookies, pie and ice cream.

Some people may be sensitive to the amounts of fructose in certain vegetables including carrots, tomatoes, beets, onions, peas and corn. Sweet breads and sweetened cereal products may pose a problem, too.

More details and guidance are available online from the University of Iowa at www.uihealthcare.com/topics/medicaldepartments/foodandnutrition/dfi/index.html.

Eliminating all fruits and a substantial number of other nutrient-rich foods may make it necessary to take a vitamin and mineral supplement. Read labels carefully, though, because some supplements contain -- you guessed it -- fructose and sorbitol.

Like so many food intolerances, sensitivity to fructose can vary from one individual to another. Some people may be able to tolerate small amounts of fructose, while others may experience symptoms after even the smallest amounts of the sugar.

Like the reader, some people may also suffer from more than one food sensitivity.

That's why most people with food intolerances could benefit from individual diet counseling from a registered dietitian. Dietitians are trained to manage complicated dietary problems and help you sort out seemingly conflicting advice and prioritize your diet goals.

If you decide to enlist the help of a dietitian, understand that not all dietitians are equally comfortable or qualified working with all types of diets. Get a referral from your health care provider or call the American Dietetic Association at (800) 366-1655 for the names of local dietitians with the expertise you need.

Suzanne Havala Hobbs is a licensed, registered dietitian and author. She holds a doctorate in health policy and administration from UNC-Chapel Hill, where she is a clinical assistant professor in the School of Public Health. Send questions and comments to suzanne@onthetable.net.