Not so fast. Here is the actual study, as opposed to a media spin or USC press release.
That is not to say that the study cannot be criticized. This is the abstract:
Mice and humans with growth hormone receptor/ IGF-1 deficiencies display major reductions in age- related diseases. Because protein restriction re- duces 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 attenu- ated if the proteins were plant derived. Conversely, high protein intake was associated with reduced cancer and overall mortality in respondents over 65, but a 5-fold increase in diabetes mortality across all ages. Mouse studies confirmed the effect of high protein intake and GHR-IGF-1 signaling on the inci- dence and progression of breast and melanoma tumors, but also the detrimental effects of a low pro- tein diet in the very old. 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.
Thanks for the link.
Skimming over the actual study, it looks worse than I had originally thought from the articles. The nutrient intake was based on a single 24 hour period... there is so much wrong with using that as a basis to make conclusions about how diet affects health across the entire lifespan that I don’t even want to touch that one. They also did cancer growth studies in mice fed “high” and “low” protein diets, then injected with cancer cells. Well, bravo, they have generated more data on cancer in mice—but whether or how that extrapolates to humans is a big guess.
In my opinion, the human data should not have been included in that study. It was, at best, marginally relevant to the rest of the study.