Grilling may be as American as, well, the Fourth of July, but what you put on your Weber and how you prepare it could affect your health. So say experts at the American Institute for Cancer Research, which is urging people to substitute veggies for meat and change their grilling habits.

AICR's warning is based on a 2007 review of research conducted on animals showing that diets high in red and processed meats increase the risk of colorectal cancer. This is the third most common cause of cancer death in the United States, according to the Centers for Disease Control and Prevention. The AICR recommends eating no more than 18 cooked ounces of red meat per week -- the equivalent of about four quarter-pound hamburgers -- and avoiding all processed meats, including such summer favorites as hot dogs and sausages.

Cooking meats such as beef, fish and pork at high temperatures produces carcinogens -- substances that can cause changes in DNA that may lead to cancer. The AICR and the American Cancer Society recommend these steps to reduce risk:

• Select lean cuts of meat and limit portion size.

• Place aluminum foil with holes over the grill to prevent fat from dripping and causing flare-ups that can deposit carcinogens from smoke onto the meat.

• Marinate meat for at least 10 minutes before grilling. Research suggests that soaking meat in any acidic liquid reduces the formation of carcinogens.

• Pre-cook meat briefly in the microwave before grilling to reduce the amount of juices that can hold carcinogens.

• Flip the meat often to reduce the temperature on both sides.

• Avoid eating charred parts of meat.