Does Too Much Protein Cause Cancer?

This question originally appeared on Quora. Answer by Keck Medicine of USC.

The next time you’re tempted to hit the drive-thru, consider ordering a veggie burger instead. Why? As delicious as a classic burger dripping with American cheese is, if you’re middle aged, extra protein in your diet can up your risk of dying from cancer by 4 percent, found a study.

It’s not only cancer you need to be concerned about.

During the duration of the study, meat-lovers were:

• 74 percent more likely to die of any cause
• Several times more likely to die of diabetes

Even if you rank in the moderate category of protein consumption, you may still be three times more likely to die of cancer than those who get less than 10 percent of their calories from protein.

The study examining 6,318 adults over the age of 50 of all ethnicities, education levels and health backgrounds, was published in Cell Metabolism and authored by Valter Longo, professor of biogerontology at the USC Davis School of Gerontology and director of the USC Longevity Institute.

How Much Protein is Too Much?

On average, you should aim to eat about 0.8 grams of protein per kilogram of body weight, according to the study and several leading health agencies. That means if you weigh 160 pounds, you should eat no more than 60 grams of protein daily. To put that in perspective, one cup of chicken breast has 43 grams of protein or about ⅔ of your recommended amount of protein. If you eat meat of any kind (poultry, beef or pork) at lunch and dinner, chances are, you’re eating too much protein.

For the study, the researchers used the following definitions:

• High-protein diet = 20 percent of calories or more from protein, including both plant-based and animal-based protein
• Moderate-protein diet = 10 to 19 percent of calories from protein
• Low-protein diet = 10 percent of calories or fewer from protein

In the study, the average diet included 16 percent of total daily calories from protein with about two-thirds from animal protein. Beans and other plant-based proteins did not show the same detrimental effects. The amount of carbs and fat a person ate did not seem to play a role in rates of cancer or death.

What Can You Do?

The obvious answer, that you may not want to hear, is cut back on protein, especially from meat, cheese and other dairy. “The majority of Americans are eating about twice as much proteins as they should, and it seems that the best change would be to lower the daily intake of all proteins but especially animal-derived proteins,” Longo said. “But don’t get extreme in cutting out protein; you can go from protected to malnourished very quickly.”

The good news is that even going from a diet with moderate levels of protein to one with low levels reduced likelihood of early death by 21 percent.

And, interestingly, you can start increasing your protein intake when you turn 65-years old and protein begins protecting against frailty and muscle-loss. The study showed that those over 65 who ate a moderate- or high-protein diet were less susceptible to disease.