Finally I get to post about something not too many people are questioning..Protein overconsumption! 😀
Whether I talk to a body-builder or a dietician, health effects of eating too much protein do not seem to be on anyone’s radar (unless a kidney disease is suspected).
Beef it up!
In developed countries people are eating approximately 30% more protein than the RDA recommended intake (1.2g of protein/kg of body weight/day vs. 0.83g RDA). Yet this is considered harmless or even beneficial (for satiety, obesity prevention). In general, we can think of all kinds of anti-fat or anti-sugar arguments, yet protein seems to be the nutrient we don’t need to worry about. There are many protein-enriched snacks and drinks that seem to have a health halo effect. I think people are not even sure why the label claim “x grams of protein!” seems exciting or promising some sort of a benefit (unless one is a gym enthusiast). Perhaps it is the fact that we don’t know any “bad” health effects of this nutrient.
Longevity & health studies
In terms of living longer, calorie restriction(CR) is the only non-genetic intervention that can lead to life extension in different organisms (from yeast to rodents to monkeys and supposedly humans). Calorie restriction means reduced energy intake (moderate CR is about 30% less calories than recommended) without malnutrition. Studies on the famous Okinawa centenarians suggest it is their moderate eating that contributes to health and longevity.
So CR should not be confused with starving or extreme undereating- many people and cultures might do so without much thought- eating about 1700 calories/day for a person with 2000 being a goal is already calorie restriction.
In mice CR studies, general CR increases longevity and induces a reduction in the level of IGF-1 (insulin-like growth factor 1). IGF-1 is an important growth factor that mediates the growth of cells and inhibits apoptosis (cell death); it is IMPORTANT because there is considerable evidence that a reduction in IGF-1 signaling plays a key role in modulating cancer and aging in humans and rodents. HOWEVER, for us humans CR does not reduce IGF-1 concentration unless protein intake is also reduced. This suggests that protein intake is more important than calorie intake in terms of IGF-1 levels in humans.
Median protein requirement for a healthy adult, by the way, is 0.65 g/kg/day. Decreased protein intake discussed with CR does not go below this number.
I first came across the idea of not going crazy on the protein while reading about mTOR. The mammalian target of rapamycin (mTOR) signaling system seems to be connected with aging and cancer
development (also cardiovascular and neurodegenerative diseases). The insulin/IGF-1/mTOR pathway is downregulated by calorie restriction, and in turn activates other anti-aging pathways in mammalian cells.
It is necessary to see more human studies with caloric and protein restriction and the effect on health and longevity. We all know overeating is not great- it does lead to weight gain and associated health issues. But it also might be speeding up our aging, wear&tear, and increasing chances of various chronic diseases. This could be crucial for a culture that believes protein to be a healthy macronutrient which needs no limitation 😉