A study published this month on Cell Metabolism1 reveals that a diet high in meat proteins increases the risk for health-related diseases, whereas a diet rich in plant proteins does not show the same adverse effects.
The team guided by Dr. Longo at the University of Southern California analyzed a nationally representative study sample of 6,381 subjects from the National Health and Nutrition Examination Survey (NHANES) III program with an average age of 65 years. Considering the entire group, a high and moderate protein diet was positively correlated with diabetes-related mortality, but not cancer mortality. When the population was divided into two groups – 50-65 years and 65 and older- , the protein intake showed different effects on subjects’ health. Subjects in the midlife group, consuming a high protein diet had a 74% increase in the risk of all-cause mortality and four-times increase in the risk of cancer mortality compared to the low protein group. In contrast, a high protein diet did not have the same negative effects on elderly subjects. Elderly subjects consuming a high protein diet had a reduction in both all-cause (23%) and cancer mortality (60%), when compared to a low protein diet. This may be due to the fact that elderly people have impaired digestive and nutrient absorption abilities that can cause malnutrition and frailty; therefore a higher protein intake is beneficial at older ages to prevent diseases.
The authors link the effect of protein consumption on mortality to the insulin-like growth factor 1 (IGF-1) , showing that in humans an increase in IGF-1 is correlated with an increased risk of cancer in subjects 50-65 years old with a high protein diet. Instead, IGF-1 levels decrease in elderly subjects. They also performed experiments in mouse models demonstrating that a low protein diet is responsible for smaller melanoma and breast cancer cell derived tumors with circulating levels of IGF-1 correlating with the protein content in the diet. However, the mechanism of IGF-1 involvement in protein intake and mortality is not well elucidated.
Despite the lack of a well-defined mechanism, this study demonstrates that a low protein diet in middle age people is beneficial for preventing cancer mortality through “at least, in part, regulating circulating IGF-1″. These findings are important in a country, the United States, where adults consume 1.0–1.3 g grams of proteins/kg of body weight/day, instead of the 0.7 to 0.8 g of proteins/kg of body weight/day recommended by the Food and Nutrition Board of the Institute of Medicine. According to previous reports, this study also shows that plant proteins, such as legumes, do not have the same unfavorable effect of animal proteins; in contrast, their intake has beneficial effects at all ages!
Beans might be healthier than hamburgers!
1. Morgan E. Levine, Jorge A. Suarez, Sebastian Brandhorst, Priya Balasubramanian, Chia-Wei Cheng, Federica Madia, Luigi Fontana, Mario G. Mirisola, Jaime Guevara-Aguirre, Junxiang Wan, Giuseppe Passarino, Brian K. Kennedy, Min Wei, Pinchas Cohen, Eileen M. Crimmins, Valter D. Longo. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell Metabolism, 2014; 19 (3): 407-417 DOI: 10.1016/j.cmet.2014.02.006