The American Institute for Cancer Research has issued warnings about grilling meat, fish and poultry — including the beloved backyard barbecue burger.

“There is enough experimental evidence to suggest that grilling certain foods increases cancer risk,” says AICR dietitian Alice Bender, M.S., R.D. “Muscle meats are the problem; substances are formed when these are grilled with intense heat. Cooking meats on any high temperature has the same effect — it’s just that grilling is traditionally done on high heat all the way and is therefore riskier.”

What happens is that intense heat causes a reaction in the muscle proteins and two carcinogens — possibly DNA-altering, cancer-causing substances — form: heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). The fattier the meat, the higher the risk.

“When fat drips, it cause the flames to leap up and increases the temperature,” explains Bender.

There is no evidence of any risks with grilling non-meat items: “Eat all the charred veggies that you want,” Bender says, but never eat charred meats or fish.

“It is very likely that it is carcinogenic,” she warns. “There’s enough evidence in lab studies to tell us that avoiding it is prudent. You can still have a backyard barbecue this summer. People are not going to give up their beloved burgers and steaks — just lessen the risks.”