Mythbuster - Does fruit contain adequate amounts of protein and other fruit facts.

I’m sure you’ve heard that protein is the main building block of the human body but did you know that the digestive tract has to break down nearly all of the protein consumed into individual Amino Acids (Free Amino Acids – FAAs) before they can be utilized by the body to build more proteins? (http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_aacids.html) That's wasted energy that you could be using for other activities.

Just this understanding alone would seem to point to the fact that we should be measuring the Free Amino Acid content of foods before relying on the protein content for nutrient availability and density.

So how important is protein? To put it into perspective, a newborn baby typically triples his/her body weight in the first year of growth while the percent of protein contained in mother’s milk is less than 1% (see https://www.ncbi.nlm.nih.gov/pubmed/392766). The fact that a newborn baby triples his/her body weight in the first year of life would appear to be at odds with the amount of protein found in the mother's breast milk, but in reality breast milk contains an abundance of free Amino Acids which can immediately be used by the infant to build the types of proteins it needs in order to grow (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3967730/) “Exclusive breastfeeding for the first six months of life optimizes infant growth, development, and health and is beneficial to maternal health. Breast milk contains adequate nutrients, minerals, vitamins, and water for growing, but for reasons not completely understood, the mammary tissue of most mammals produces large amounts of non-protein nitrogenous compounds, including free (protein-unbound) amino acids (FAAs)”

It amazes me that many researchers fail to connect the dots. The reason mother's milk contains an abundance of free Amino Acids is one of efficiency. Nature is the queen of efficiency so why would Nature design mother's milk to contain lots of protein, that the body needs to be break down into free amino acids before it can utilize them, when it is much more efficient to have the mother's milk contain an abundance of free amino acids that are immediately available with very little work needed to be done by the digestive tract of the infant.

While I realize that the above appears a little off topic, it does help to answer the question “does fruit have protein?”

First and foremost – all fruit contains protein – and while fresh, RIPE fruit may not contain large amounts of “protein”, fresh, RIPE fruit does contain an abundance of free amino acids which are the building blocks of protein and which are readily absorbed in the digestive track.

To date, most research into the nutrient content of fruit and vegetables has focused on the amount of protein while there has been little research on the amount and type of free amino acids contained in fruit and vegetables. In the little research that has been done, it has been found that during the ripening process, which is when protein content is at its lowest and the time when researchers generally test the protein content of fruit, proteins are being broken down by different protease into free amino acids (https://www.ncbi.nlm.nih.gov/pubmed/19876714).

Some examples of the free amino acids found in fruit –

Pawpaw – The most abundant free amino acids were arginine, glutamine and serine. Also present were isoleucine, leucine, methionine, phenylalanine, tryptophank and tyrosine – all of which are essential amino acids.

Tomato – “free amino acids increase dramatically during fruit ripening and their abundance changed differentially” (https://www.ncbi.nlm.nih.gov/pubmed/19876714)

Apples – alanine, asparagine, arginine, carnosine, citrulline, cycstine, cystathionine, ethanolamine, glutamine, glycine, histidine, isoluecine, leucine, lysine, mathionine, ornithine, phosphoethanolamine, phenylalanine, serine, proline, sarcosine, serine, taurine, threonine, tryptophan, tyrosine and valine. (see the Australian Journal of Crop Science – http://www.cropj.com/maro_5_2_2011_154_161.pdf)

Muskmelon (cantaloupe) - https://pubs.acs.org/doi/abs/10.1021/jf9503568?journalCode=jafcau

Another important point is the amount of energy required for the human body to break down protein. Called the "thermic effect of food" the human body uses 20-35% of it's energy to break down protein - WOW! I'll bet that you could find much better uses for that energy.

So the next time you hear that there is not enough protein in fruit you'll know the truth that fruit actually contains something much better - Free Amino Acids which are the true building blocks of the human body!

Here are some other examples of the way in which Nature prepares fruit for us -

1. Besides being the building block of proteins, free amino acids provide another bonus. During the ripening process, in conjunction with other chemical constituents, free amino acids are responsible for producing many of the smells and flavors (called volatile compounds by science) our senses respond to. This is why the flavor is so much better when fruit is harvested when RIPE! (Page 34 - http://priede.bf.lu.lv/grozs/AuguFiziologijas/Augu_resursu_biologija/gramatas/Handbook%20of%20Fruit%20and%20Vegetable%20Flavors.pdf)

2. Chlorophyll (responsible for the green color of the leaves and fruit when unripe) is broken down into nonfluorescing chlorophyll catabolytes which are highly active anitoxidants (https://onlinelibrary.wiley.com/doi/full/10.1002/ejoc.200800804)

3. The human body must break down fats into fatty acids for assimilation and, of course, Nature does this for us as well by increasing the amount of fatty acids as the fruit is ripening. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5050263/) & (https://pubs.acs.org/doi/abs/10.1021/jf60187a027?journalCode=jafcau). Some of these fatty acids also become part of the process of creating the smells and flavors of ripe fruit that we enjoy.

NOTE - The thermic effect of breaking down fat into fatty acids is between 5% - 15% of the bodies energy.

1. The human body must break down complex sugars (starch) into simple sugars and once again Nature does this for us when the fruit is ripening. (Page 1 - https://onlinelibrary.wiley.com/doi/pdf/10.1016/0307-4412%2894%2990098-1)

Note - The thermic effect of breaking down starch into simple sugars is also between 5% - 15% of the bodies energy.

To sum it up the total thermic effect of consuming protein, fats and starches (complex carbohydrates), the body must use between 30% - 65% of it's energy to digest them - WHAT A WASTE OF ENERGY. If you could increase the gas mileage in you car by 30% - 65% would you do it?

A simple test that you can perform is to notice how you feel after a large meal of pasta or meat on an empty stomach - sluggish perhaps? Then notice how you feel after eating a large quantity of fruit on an empty stomach - energized perhaps? When the food we eat is already prepared for us the way Nature does it, our digestive system doesn't need to use the enormous amount of energy needed to break down protein, fats and complex sugars into their basic components of amino acids, fatty acids and simple sugars and that energy can be used to ramp up an active and fulfilling lifestyle.

Peace.