WALNUT CREEK, Calif. — Organic became the nation's fastest growing food segment largely on claims that it's safer and healthier than conventional fare, but according to a new report such conclusions are premature.

The study, a survey of existing literature co-authored by a University of California at Davis food toxicologist, does not ultimately assert that one production method is superior to another, but it suggests there could be trade-offs and argues additional research is necessary to determine the benefits and risks of each.

"I'm not convinced there is any difference in the health and safety of organic and conventional foods," said Carl Winter, director of the FoodSafe Program at UC Davis. "There is still a lot of speculation, still a lot of research that needs to be done."

Winter co-authored the peer-reviewed paper with Sara Davis of the Institute of Food Technologists, a Chicago-based nonprofit organization that promotes the use of technology in agriculture. The IFT published the review in its Journal of Food Science in December.

The report makes three main points:

• Research has consistently shown organic foods contain less pesticide residue than conventional food, but "the marginal benefits of reducing human exposure to pesticides in the diet through increased consumption of organic produce appear to be insignificant."

• Some studies indicate organic production methods result in higher nutrient levels, but the same mechanisms that can produce potentially beneficial things like polyphenolic compounds may also generate higher levels of toxins such as glycoalkaloids in potatoes and tomatoes.

• Some research suggests the widespread use of animal manure as fertilizer in organic production can, when composted improperly, result in a higher occurrence of pathogens than conventional farming.

Organic food sales have grown by about 20 percent annually since 1990 and hit $13.8 billion in 2005, and proponents disputed several of the report's suggestions.