PROTEIN

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.

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mTOR
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.

Conclusion
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 😉

Some LINKS:

Why Protein is the new “It” Ingredient

http://online.wsj.com/article/SB10001424127887324789504578384351639102798.html

Macronutrient Balance and Lifespan

http://www.impactaging.com/papers/v1/n10/full/100098.html

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U[mmm]ami.

Some people claim they “crave” protein in their food to feel satisfied… others say it is really the fat that they are after. Do we really crave protein? Can we even “taste” protein in itself?

I used to think that we do not.. until we got on the topic of UMAMI in class. In 1908 Kikunae Ikeda identified the unique taste component of kelp (seaweed) as the salt of glutamic acid (most abundant amino acid in the diet). He used umami(=”savoury deliciousness”)  to describe it, which to a Westerner translates to meaty, broth-like, savoury. Other umami substances are0 inosinate and guanylate

pic_umami_01Umami- the 5th Taste

Glutamate is found in both animal and plant foods; in almost all protein-containing foods (fish, meat, poultry, eggs, cheese), many vegetables (ripe tomatoes, cabbage, maize, green asparagus) and for humans & chimps, in mother’s milk. In addition, glutamate is produced by our bodies and binds with other amino acids to form structural proteins.

The taste of glutamate (on its own + in combination with IMP5 ribonucleotide) is thought to represent the taste of protein (evidence is still scarce). Glutamate has a special quality of enhancing certain flavor characteristics of food (sugar, salt, fat). * Umami, by the way, is tasted by humans and dogs (rats can’t seem to taste it as much). Currently, umami is recognized as the 5th basic taste (others: salt, sour, bitter, sweet)

Wait a second…Glutamate!?

If you’re at all into health, the word “glutamate” has probably evoked some negative connotations. Or- monosodium glutamate- the evil MSG. While umami exists naturally, MSG is a additive (extracted glutamate mixed with salt) which has become quite unpopular in the 90s due to health concerns (for health issues, please google MSG; that’s a whole other topic). If you use MSG, you taste umami, but umami does not contain MSG (MSG on its own does not taste good but enhances flavor of other foods). I suppose the original idea was to add umami-tasting MSG to healthy but often disliked foods such as bitter vegetables to increase their intake…of course  now you find MSG in many processed nutritionally poor products (it’s probably not too great to increase our liking of those foods).

UnknownIn conclusion….can we crave protein specifically? Indeed it seems so. The study I reference at the bottom argues that the taste of MSG maybe one of the compounds that represents the taste of dietary protein…this “meaty” umami taste appears to predict the liking and preference for high protein foods.

In fact, I now realize why seaweed, especially dulce flakes were quite popular with my raw vegan friends. We just loved seaweed– it seemed to fill us up when added to raw vegetable dishes. I suppose the umami taste, which is associated with meatiness and richness, might impose the feeling of satisfaction with one’s meal. Note: This website has a fantastic post about umami & being vegan!: http://www.theveganrd.com/2012/04/is-umami-a-secret-ingredient-of-vegan-activism.html

Opinion: While clinical studies do not support the negative health claims of MSG, we could always be weary of natural compounds being extracted and concentrated in unnatural amounts.  So far, it seems that any time a human tries to improve on nature in a lab, the results tend to be disappointing. Want to experience more umami- add sun-dried tomatoes/miso/organic soy sauce to your dish instead (mmm) ;D

*Luscombe-Marsh, N. D., Smeets, A. J. P. G., & Westerterp-Plantenga, M. S. (2008). Taste sensitivity for monosodium glutamate and an increased liking of dietary protein. The British journal of nutrition, 99(4), 904–8. doi:10.1017/S000711450788295X