Large 20-year study shows that a high-protein diet rich in fibre-less animal products, is deadly: Part 2

Large 20-year study shows that a high-protein diet rich in fibre-less animal products, is deadly: Part 2

“[This study] is interesting in that the issue appeared not to be fat, as we have largely assumed, but animal protein.  I think it supports recommendations to eat less meat.  Make fruits, vegetables, and grains the focus of your diet instead…”
Sharecare’s Chief Medical Officer Dr Keith Roach, MD.

In another interesting aspect to this research, a 2,253-strong randomly selected smaller portion of the study participants, levels of the growth hormone IGF-I were recorded.  The researchers found that for every 10 ng/ml increase in IGF-I, those on the high-protein diet were 9% more likely to die from cancer than those on a plant-based wholefood diet.  This confirms earlier research linking IGF-I levels to cancer risk.

“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”
Co-author Eileen Crimmins, the AARP Chair in Gerontology at USC, March 2014. 

Salvatore Caruso, 108, is the second oldest man in Italy and lives in the small Italian town of Molochio, with one of the highest prevalence of centenarians in the world.  He has eaten a low-protein, plant-based diet for the majority of his life.

“People talk about a balanced diet but no one knows what it is, particularly in terms of the balance of macronutrients, the ratio of protein to carbohydrate to fat.  If people want to live long, healthy lives they can look at their diet and exercise.  That will do more good than taking all the pills in the world”
Co-author Professor David Le Couteur, a co-author of the mouse study from the Charles Perkins Centre at the University of Sydney, March 2014.

“This paper is suggesting significant changes to the recommended protein intake in terms of age — how much protein at what age — and we’re not ready to do that yet”
Roger Clemens, adjunct professor of pharmaceutical sciences at the School of Pharmacy, March 2014.

“Some critics are trying to debunk our research, but don’t understand how we generated these numbers.  We used a statistical algorithm that adjusted for groups like age … and a lot of people are missing the point of that”
Co-author Dr Morgan Levine, a National Institute of Aging predoctoral fellow working at the Davis School of Gerontology (citing the fundamental differences between researchers focused on nutrition versus those focused on disease and longevity).

The mice study
Researchers also looked at the same thing in mice and cellular models.  In the most comprehensive study of its kind, the scientists fed almost 900 mice on one of 25 diets, each with a different ratio of protein, carbohydrates and fat, and/or with reduced total energy content.  The researchers found a longer lifespan, fewer age-related health problems, much lower cancer incidence and 45% smaller average tumor size in mice on a low-protein diet.  These mice lived, on average, 50 weeks longer than mice on high-protein diets (this is a long time in a mouse-life).  The mice on high-protein, low-carbohydrate diets had shorter lifespans and poor heart health.

Study by 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” from the National Health and Nutrition Examination Survey (NHANES III) data, as published in Cell Metabolism, 2014; 19 (3): 407-417 DOI: 10.1016/j.cmet.2014.02.006.  The research was funded by the National Institute of Aging of the National Institutes of Health (grants numbers AG20642, AG025135, AG034906, P30AG017265 and T32AG0037) and a USC Norris Cancer Center pilot grant with additional information from the University of Southern California.  As published in Science Daily, Medical Daily, CBS News,, AAP, The Sydney Morning Herald, Scientific American, The Guardian, March 2014.


Posted: Saturday 22 March 2014