Most of us know that smoking cigarettes is not a good idea, but we hardly think twice about eating meat and cheese which are high in protein. It turns out that excessive protein consumption is dramatically linked to a rise in cancer mortality. New research shows that middle-aged people who regularly eat a lot of animal protein such as meat, milk and cheese, are generally more susceptible to early death. Researchers found a definitive correlation between high protein intake and mortality risk for the first time in a University of Southern California study.

It’s hard to believe that if you are middle aged, a high-protein diet causes you to be nearly twice as likely to die, and four times as likely to die of cancer. Most of us do not even know just how much protein is appropriate to eat. The topic of protein consumption has become quite a controversial topic since the confusion that’s been brought about through protein-heavy diets including Atkins and Paleo. Fans of protein-rich foods were 74% more likely to die of all-cause mortality than their counterparts who ate a low amount of protein during the study period. Those who ate more protein were also several times more likely to die due to diabetes.  

The latest research considers how biology changes as people age, instead of only looking at adulthood as one single phase of life. This means that something good for you at one age, may actually be harmful at a different age. Protein controls IGF-I, a growth hormone that has been linked to cancer susceptibility. IGF-1 levels dramatically drop after age 65, which leads to frailty and potential muscle loss. This study showed that high and even moderate protein intake at middle age is very damaging, but moderate- to high-protein intake is protective for older adults. It is recommended for adults to consume 0.8 grams of protein per kilogram of body weight per day, the equivalent of someone who is 150 pounds eating 54 grams of protein. To put it into perspective, a “high-protein” diet is anything above 20% of total daily calories from protein. A “low-protein” diet will be less than 10% of total calories from protein.

The takeaway message here is that a low-protein diet in middle age is useful to prevent cancer and overall mortality, whereas older adults should avoid very low-protein diets to maintain healthy weight and protection of frailty. Another interesting finding was that plant-based proteins did not have the same mortality effects as animal proteins did. Also, controlling carbohydrate or fat consumption did not affect cancer or death rates, suggesting animal protein to be the main culprit.