Eating more processed meats such as bacon, sausage and smoked ham increases the risk of stomach cancer, Swedish scientists said on Wednesday.

A review of 15 studies showed the risk of developing stomach cancer rose by 15 to 38 percent if consumption of processed meats increased by 30 grams (1 ounce) per day, the Karolinska Institute said in a statement.

Stomach cancer accounts for nearly one tenth of total deaths from cancer, the institute said.

The research, published in the Journal of the National Cancer Institute, collated studies covering 4,704 individuals between 1966 and 2006 and showed “unequivocal” results, the institute said.

“Nobody had carried out this type of analysis into processed meats and stomach cancer,” said Susanna Larsson, one of the authors of the study at the institute. “And our results from a mean value show very clearly that there is an association between increased consumption of processed meat products and stomach cancer.”

The institute said processed meats were often salted or smoked, or had nitrates added to them, in order to extend their shelf-life, which could be connected to the increased risk of stomach cancer, the fourth most common type of cancer.

“We hope that further studies will clarify the interaction between the consumption of processed meats and other factors, such as other dietary factors and the effects of different bacteria on the incidence of stomach cancer,” Larsson said.