Protein

Ah yes - protein. A much discussed topic in today’s world. Protein is such an important nutrient in the body. It is responsible for cellular structure, make up hormones, enzymes, and a variety of reactions in the body. Hemoglobin is a protein that transports oxygen around the body. Antibodies are proteins that protect us from foreign invaders. So, because it is so important and such a hot topic - it deserves a well researched, in depth view. I encourage you to look at the sources cited and other peer reviewed, up to date research papers. 

The Building Blocks 

Ok so let’s get started. Protein is made from amino acids. Amino acids are made from the α-carboxyl group, a primary α-amino group, and a side chain called the R group. The R group will determine if it is acidic, basic, or neutral which would then in turn impact its function. It has been known that there are 20 amino acids the human body uses, but science is ever evolving and humans are just scratching the surface of understanding Mother Nature and so two new amino acids have been described in research papers- selenocysteine and pyrrolysine. Selenocysteine is in fact made in the human body pyrrolysine is not, but is used by some species of bacteria and archaea. There are nine essential amino acids that the body does not produce but needs and will have to get from foods- histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

What about too much protein? 

So the protein intake is not the only thing that matters, but the amount of which type of amino acid is being ingested can also have an impact. All protein from plants are complete sources of protein. Meaning they contain all nine essential amino acids needed. Almost all animal sources are complete with the exception of gelatin which does not have tryptophan. However, the composition of amino acids in protein sources can differ and sometimes you do not want too much of one. Methionine is an amino acid that can, in excess quantities, cause the mitochondria to produce more free radicals. This was shown in a lab test when the amino acid was put with isolated mitochondria. In a study with rodents, it was only when protein was cut, not carbohydrates or fats, was there a decrease in mitochondrial free radicals, decrease in mitochondrial DNA damage, and an increase in longevity- reduced methionine intake specifically was a key driver of these results. Plant sources of protein have much lower levels of methionine than animal protein. 

When we eat large amounts of protein or even modest amounts of animal protein we see a rise in IGF-1, a growth hormone, which sends a signal to our cells to grow and grow and use the protein as building blocks. But what else grows and grows? Cancer cells. Excess growth may lead to excessive cellular growth as we see in cancer cells (Greger, 2023, p. 73). Stimulation of IGF-1 is decreased when protein is restricted. IGF-1 rise is also more predominant when animal protein is consumed. 

Why does animal protein spur more 1GF-1 than plant protein? To explain this it is nice to use carbohydrates as an analogy. There are some food sources that contain simple carbohydrates such as table sugar and so your blood sugar levels rise fast, but there are complex carbohydrates that take time for your body to break down such as quinoa and sweet potato and so do not spike blood sugar levels. Similarly, because animal protein is very similar to our body’s own protein composition, the liver breaks it down fast. On the contrary, plant protein is broken down much more slowly because plant protein is not similar to our human protein composition  not causing a surge in IGF-1. You’ll sometimes hear higher quality protein is something that has a protein composition similar to our own, but that in of itself is not a positive aspect.  IGF-1 also does not seem to impact lean mass or muscle strength (Greger, 2023, p. 74).  If you need someone to explain it better Dr. Michael Greger has created a video on IGF-1 which I will link here. All of this information has been gotten from the book How Not to Age by Dr. Michael Greger. 

There is a plant source of protein that is similar to that of animals - soy protein. Research shows that consuming 40 grams of soy protein supplements increase IGF-1 but not a couple servings of soy foods a day (Greger, 2023, p. 74).

When protein is restricted mTOR is also decreased. 105. When the enzyme mTOR is activated it may suppress autophagy. 24-25. Autophagy is your body’s cleaning mechanism, a way for it to get rid of not only fat stores, but also old protein molecules, organelles and more that are not functioning properly anymore. A decrease in mTOR may just help your body reboot itself. Protein intake can drive up mTOR, especially amino acids methionine and branch chain amino acids (BCAA) which include isoleucine, leucine, and valine. 105. Animal protein contains these amino acids more than plant protein (Greger, 2023, p. 105).

How much protein do you actually need? 

Ok so how much protein do we actually need? The WHO/FAO/UNU has stated that the median adequate protein requirement for individuals is 0.66g  per kg of body weight, but the report takes into account that everyone is different and so to capture the varying needs of protein intake  states 0.83 g of protein per kg of body weight as the required protein amount. Dr. Micahel Greger gives a range of 0.8-0.9 grams of protein per kilogram of body weight. What about protein supplements and bulking? In a meta-analysis it was shown that protein supplementation only increased strength by 2.29 kg of one repetition maximum test and increased fat free muscle mass (FFM) by only 0.3kg more than the group not taking protein supplements. FFM excludes only the weight of fat and includes not only muscle but also water, bone, and organ mass. No improvements were made when protein consumption surpassed 1.62 g per kg of body weight. 

In the United States, protein consumption is sometimes two times as needed. This can lead to excessive levels of methionine (Greger, 2023, p. 111). So, decreasing protein intake to required levels is one way to decrease methionine intake. The other way is through you guessed it - eating more plants! Plant foods contain adequate protein intake but with the glamorous advantage of less methionine. Go ahead and load up on tofu, tempeh, legumes, nuts and seeds!

Protein in Blue Zones 

We see the benefits of not eating excessive amounts of protein in blue zones, the areas most densely concentrated with people living past the age of 100. The diet’s people living in the blue zone Okinawa consists of only 10% protein intake. The vegetarian Adventists in blue zone Lomalinda California eat next to no meat (Greger, 2023, p. 111).

Book Sources 

Greger, M. (2023). How not to age. Flatiron Books.