Want protein? Eat beans.

I just posted about mice that lived longer and healthier lives when they ate low-protein, high carbohydrate diets.  Because people will say “Great for the mice!” here’s a brand new study in humans that found the same thing:

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, March 2014

Mice and humans with growth hormone receptor/IGF-1 deficiencies display major reductions in age-related diseases. Because protein restriction reduces GHR-IGF-1 activity, we examined links between protein intake and mortality. Respondents aged 50–65 reporting high protein intake had a 75% increase in overall mortality and a 4-fold increase in cancer death risk during the following 18 years.

These associations were either abolished or attenuated if the proteins were plant derived.

There was also a “5-fold increase in diabetes mortality across all ages.”

This was an epidemiological study that tracked 6,381 US men and women, 50 and over (NHANES III), for nearly 2 decades. It included a variety of ethnicities, education levels, and health conditions.

A few more excerpts from the study:

• Notably, our results showed that the amount of proteins derived from animal sources [meat, fish, cheese, milk, eggs] accounted for a significant proportion of the association between overall protein intake and all-cause and cancer mortality. These results are in agreement with recent findings on the association between red meat consumption and death from all-cause and cancer.
• Previous studies in the U.S. have found that a low carbohydrate diet is associated with an increase in overall mortality and showed that when such a diet is from animal-based products, the risk of overall as well as cancer mortality is increased even further.
• The progression of both melanoma and breast cancer was strongly attenuated by the low protein diet, indicating that low protein diets may have applications in both cancer prevention and treatment.
• In mice, the changes caused by reduced protein levels had an effect potent enough to prevent the establishment of 10%–30% of tumors, even when 20,000 tumor cells were already present at a subcutaneous site.

So, you can have cancer, but prevent it’s progression by eating a low-protein diet.  Dr. Campbell, author of The China Study, must be breaking out the champagne.

Note, though, that when someone reached their mid-60s, a higher protein diet was found to be beneficial:

“Both high and moderate protein intake in the elderly were associated with reduced mortality compared to that in the low protein group, suggesting that protein intake representing at least 10% of the calories consumed may be necessary after age 65 to reduce age-dependent weight loss and prevent an excessive loss of IGF-1 and of other important factors.”

For these authors, less than 10% was considered low-protein, 10-19% moderate protein, over 20% high-protein.  They found that even moderate amounts of protein had detrimental effects during middle age.  However, they are advising people over 65 to get at least 10% of their calories from protein.  Note, however, that risk for diabetes was still 5-fold at those older ages.  So the protein they should be consuming should come from plant sources. Bean, legumes, peas, peanuts, soy products, nuts, and seeds are excellent sources of plant protein.

“These results suggest that low protein intake during middle age followed by moderate to high protein consumption in old adults may optimize healthspan and longevity.”

Here’s co-author of the study, Valter Longo (Professor of Biogerontology at USC Davis School of Gerontology, Director of USC Longevity Institute), from their press release:

“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.”

“Almost everyone is going to have a cancer cell or pre-cancer cell in them at some point. The question is: does it progress?” Longo asked. “Turns out one of the major factors in determining if it does is protein intake.”