ITHACA, N.Y. — A major dietary study suggests that humans are a vegetarian species whose risk of disease is increased by eating meat and animal products, says a Cornell University researcher.

A plant-based diet is more likely to promote good health and reduce the risks of heart problems, cancer, diabetes, osteoporosis and other diseases, according to the preliminary findings of the continuing study in China.

“People who eat mostly plant foods and a generous variety of plant foods … that is the kind of diet that is most likely to be associated with reduced risk of the kinds of disease that tend to kill us in this country,” said T. Colin Campbell, a nutritional biochemist who directed the continuing study.

Other dietary studies reached similar conclusions focusing on one aspect of a specific disease or on individual foods or nutrients, but none has taken such an extensive look at “the total dietary pattern effect,” said Campbell.

“Animal foods, in general, are not really helpful and we need to get away from eating them,” he said.

Only in the last few thousand years have meat and animal products become staples of our diet. “That’s not nearly enough time to evolve new mechanisms to give us protection from those kinds of foods,” said Campbell, who is writing a book on the reasons humans have turned into carnivores.

The study began in 1983 to explore dietary causes of cancer but was expanded to include heart and metabolic diseases and a variety of infectious diseases. Aiding Cornell in the study are scientists from the Chinese Academies of Preventive Medicine and of Medical Sciences and the University of Oxford.

Scientists surveyed 6,500 Chinese, each of whom contributed 367 facts about their diet. The preliminary findings will be reported in a 900-page monograph to be published next month by Cornell University Press.

Campbell said there were several provocative findings regarding proteins, fat and cholesterol among the roughly 8,000 correlations that were found statistically and biologically significant in the study.

The study found that the Chinese consume one-third less protein than Americans and that only 7 percent of their protein comes from animal sources, compared with 70 percent for Americans.

“The dietary guidelines that have been formulated in the West rather incorrectly protect our intake of animal protein. Consumption of animal protein itself also raises the risk of cancer and heart disease,” he said.

Previous studies have urged reducing dietary fat to less than 30 percent of an individual’s daily caloric intake to curb the risk of heart disease and cancer. But the Chinese study suggests that fat should account for a maximum of 20 percent — and preferably only 10 to 15 percent — of calories.

Campbell said the Chinese consume 20 percent more calories than Americans do, but Americans are 25 percent fatter. That’s because Chinese eat about a third of the fat that Americans do and twice as much starch.

The study also found that the Chinese had a lower cholesterol level than Americans, who consume more animal foods and dairy products.