“That chicken wing you're eating could be as deadly as a cigarette.”

This is according to a study by the University of Southern California.

Published in Cell Metabolism, the study shows that middle-aged adults who eat a high-animal-protein diet (milk, meat, and cheese) are more likely to die of cancer than those who eat a low-protein diet. Researchers also found that those who ate large amounts of meat and dairy were more likely to die at an earlier age.

Data was collected from more than 6,300 adults over the age of 50, and participants were divided into three categories:

High-protein eaters—20 percent of daily calories from protein

Moderate-protein eaters—10 to 20 percent of daily calories from protein

Low-protein eaters—no more than 10 percent of daily calories from protein

Those who consumed the highest levels of protein were 74 percent more likely to die for any reason during the 18-year span of the study—they were also several times more likely to die of diabetes complications.

How much protein should we eat?

This controversial topic has been muddled by fad diets such as Atkins and the Paleo diet. Past research has considered how biology changes as we age. “In other words, what’s good for you at one age may be damaging at another. Protein controls the growth hormone IGF-I, which helps our bodies grow but has been linked to cancer susceptibility. Levels of IGF-I drop off dramatically after age 65, leading to potential frailty and muscle loss,” says Suzanne Wu of USC.

The study shows that high-protein intake during middle age may be quite harmful. But, those who were over 65 and ate a moderate- to high-protein diet were less susceptible to disease.

The benefits of a plant-based diet

Researchers found that plant-based proteins were not as detrimental to participants' health as animal-based proteins. Good plant-based sources of proteins include:

Vegetables—avocado, broccoli, and dark leafy greens

Beans—legumes, lentils, soybeans, and garbanzo beans

Nuts and seeds

Grains—oatmeal, quinoa, and brown rice

The Centers for Disease Control recommends that 10 to 35 percent of your daily calories come from protein, and they also provide a breakdown for how much you need based on your age.