Many Americans believe they have lactose intolerance and thus avoid dairy products, but no one really knows whether they are damaging their health, experts told a national conference on Wednesday.

In fact, no one has even done the research needed to tell how many people have actual lactose intolerance, which makes it difficult or impossible for them to digest milk, cheese or yogurt, the experts told a "consensus conference" at the National Institutes of Health, a meeting called to define the state of science.

"I think that there are huge gaps in knowledge," Dr. Frederick Suchy of the Mt. Sinai School of Medicine in New York, who led the meeting, told a news conference.

"There is a huge amount of research that needs to be done."

And while there is a great deal of worry that people who avoid dairy are missing out on calcium and vitamin D that can keep their bones strong, minimize high blood pressure and perhaps even prevent some cancer, there is no evidence this is in fact the case, Suchy said.

Many new products claim to help people with lactose intolerance drink milk without bloating, cramps, diarrhea and other ill effects but no one has studied those, either, Suchy said.

MORE RESEARCH NEEDED

Calcium and vitamin fortified orange juice, soy milks and other products should, in theory, provide the nutrients, he said.

"Although dairy foods are an excellent source of calcium, vitamin D, protein, magnesium, potassium, riboflavin, and other nutrients, these individual nutrients are available in other foods, fortified foods, and supplements," the final report from the conference reads.

People who think they must avoid all dairy products may not need to, the researchers said in their report.

"The available evidence suggests that adults and adolescents who have been diagnosed with lactose malabsorption could ingest at least 12 grams of lactose (equivalent to the lactose content found in 1 cup of milk or 1 cup of yogurt) with no or minor symptoms," the report reads.

It calls for more research into the issue.

"Despite the widespread belief that decreased vitamin D and calcium intake associated with restricted intake of dairy products will lead to poor health outcomes, particularly related to bone mineral density and risk for fractures, few data are available on bone health in individuals with lactose intolerance and dairy avoidance," it reads.

"Future studies should investigate the association between dietary calcium intake and outcomes in people with lactose intolerance on low-lactose diets."

Most human babies are born with the ability to digest milk, but a genetic mutation allows people of mostly northern European descent to continue to eat and drink dairy products into adulthood with no unpleasant side-effects.

Conditions range from true lactose intolerance to lactose malabsorption, which is an inability to completely digest milk products.