by Mick Walker
2 years ago
What is Protein?
Proteins are large molecules and belong to the group of three MACROMOLECULES needed in our diet – the other two are Carbohydrates and Lipids (also known as Fats and Oils). All living things contain protein.
They are made up of long chains (polypeptides) of smaller molecules called Amino Acids – of which there are 20. The properties and functions of each particular protein are determined by the order of amino acids in the polypeptide chains.
In our livers, we are able to convert some amino acids to others. However, there are 8 amino acids (some sources might say 9 or 10) which we cannot make from others and must be obtained from what we eat (the so-called ESSENTIAL amino acids).
We need protein to build cell membranes, enzymes, antibodies, some hormones and molecules such as collagen and haemoglobin.
When we digest protein molecules, we absorb them as amino acids, which we then use to build our own proteins as required.
Some Protein Myths
1. A major proportion of our diet needs to be protein. It is not unusual for people to obtain as much as 35% of their calories from protein. A healthy amount would be in the region of 10%. This equates to roughly 0.8 g per kilo of body weight. For most men, this is around 56g and for women around 46 g per day.
2. It is preferable to obtain our protein from animal sources i.e. meat, dairy products and eggs.
3. If we want to obtain all our protein from plants, it is necessary to eat certain combinations of plants at each meal in order to make sure we are getting all the essential amino acids.
In fact, this myth was first suggested by Frances Moore Lappé, when she published ‘Diet for a Small Planet’ in 1970. In later editions of her book she did explain that this idea had been a mistake and that it is perfectly possible to obtain all the essential amino acids from plants as long as we eat a range of protein rich plants on a regular basis. These include all beans and lentils, chickpeas, hemp seeds and chia seeds. Soy beans (as edamame, tofu or tempeh) and quinoa are both complete sources of the essential amino acids.
Why plant protein may be preferable to animal protein
The first point to be clear about is that ALL amino acids are initially synthesised by plants and all herbivores obtain their protein requirements from plants.
It would appear that most auto-immune conditions are triggered by animal protein. Small chain of amino acids (called peptides) are absorbed into the blood and can initiate an immune response.
Animal proteins contain a much higher percentage of sulphur containing amino acids than plant proteins. These are mainly cysteine and methionine. One of the problems with this is that it can lead to the production of hydrogen sulphide in our intestines, which can then produce sulphuric acid. Such metabolites are undoubtedly detrimental to the maintenance of a healthy gut flora as well as promoting acidification of our body fluids. High methionine intake is also linked with more rapid aging and accelerating cell division, which can lead to cancer. This is possibly as a result of stimulating the release of IGF1 (Insulin -like Growth Factor)
Animal protein also contains higher levels of the amino acids leucine, isoleucine and valine, known as ‘Branched-chain amino acids’. These have now been linked to the development of insulin resistance and Type 2 Diabetes.
Finally, animal protein is known to be associated with the development of various kidney conditions as a result of putting more stress on the kidneys than is caused by eating plant sources of protein.
Recommended reading on protein nutrition from plants would be ‘Proteinaholic’ by Dr Garth Davis
A review of this book can be found at : http://www.vegancyclist.co.uk/single-post/2016/01/03/PROTEINAHOLIC-by-Dr-Garth-Davis
He has an excellent website : www.proteinaholic.com
About the Author
Mick is an Oxford educated Biologist, who has recently retired from a career in education.
In addition to teaching, he has, for many years, been a senior examiner with Cambridge Assessment. At present, he is mostly involved with international A Level Biology examinations.
In terms of diet, he has not eaten meat for approaching 40 years and has now been fully plant based for around 6 years.
As a keen cyclist, the decision to become 100% plant based was inspired by the reading of ‘Eat and Run’ by Scott Jurek, an American ultra-marathon runner.
During this time, he has studied closely the increasing evidence for the benefits of a Whole Food Plant Based diet – benefits which he himself has experienced in terms of fuelling his cycling well into his 60s!