I am always asked how much protein should I ingest daily. Unfortunately that is not a simple answer and it depends on the type of protein we are analyzing. I am sure the following will surprise a lot of people and still needs more conclusive studies.

The research shows that a low-protein diet in middle age is useful for preventing cancer and overall mortality, through a process that involves regulating IGF-I and possibly insulin levels. However, we also propose that at older ages, it may be important to avoid a low-protein diet to allow the maintenance of healthy weight and protection from frailty

High-protein diet in middle age may increase risk for diabetes, cancer, and mortality.

This data was obtained from the National Health and Nutrition Examination Survey, which followed 6,381 adults aged at least 50 years for nearly 2 decades.

Researchers defined high-protein intake as a diet deriving at least 20% of calories from protein, both plant- and animal-based. A diet including 10% to 19% of calories from protein was considered moderate, and a low-protein diet included less than 10% protein.

Overall, participants with high- and moderate-protein intake had higher risks for diabetes-related mortality compared with the low-protein intake group.

Among those in the younger group (50-65), higher protein intake increased the relative risk for death by 74%.

They were four times more likely to die of cancer compared with participants who had a low-protein diet.

Further, participants in the younger age group who ate a moderate-protein diet were three times more likely to die of cancer than those with a lower protein intake.

Although the study findings show that high-protein intake during middle age can be harmful, high-protein intake may be beneficial for older adults. Protein controls insulin-like growth factor I, whose levels dramatically decrease after age 65 years and can lead to frailty and muscle loss.

Data showed that participants aged at least 66 years who consumed high or moderate levels of protein vs. low levels of protein had a reduced risk for mortality of 28% and 21% , respectively. Additionally, high-protein consumption reduced risk for cancer mortality by 60% in this older age group.

When we examined breast cancer the type of protein may make a significant difference. Women who consumed large amounts of red meat had a significantly greater risk of breast cancer as compared with women who ate the least red meat, an analysis of the Nurses’ Health Study II showed.

Overall, the risk of breast cancer was increased by 22% among women in the top quintile of red meat consumption versus those in the bottom quintile. Intake of fish, poultry, eggs, legumes, and nuts did not significantly affect the risk of breast cancer.

The data, involving 88,803 women ages 26 to 45, also showed that replacing one serving of red meat daily with poultry, fish, legumes, or nuts was associated with a 14% reduction in breast cancer risk.

We will need to continue to develop well designed studies to further explore the relationship with protein consumption at different ages and what type of proteins are the healthiest.