Protein is no doubt an essential nutrient, crucial for building and repairing muscle tissue and maintaining a variety of other bodily functions. Protein is made up of twenty different amino acids, eleven of which are produced naturally by our body. The other nine (essential amino acids) must come from the food we eat.
There is much confusion and misinformation out there in regards to what the best protein source for humans is. I believe there are many factors that need to be taken into consideration when deciding which source is most suitable; quality, assimilation and utilisation, and the effect it has on our health. In this article I will lay out the main differences between the two sources so you can make the best decision for yourself.
Protein quality is the digestibility and quantity of essential amino acids for providing the proteins in correct ratios for human consumption. Animals have flesh like us, so not surprisingly, their proteins have a more complete and similar amino acid profile to that of humans. The same study states that proteins from animal sources provide the highest quality rating of food sources due to the ‘completeness’ of proteins from these sources. This is the main reason people think animals are the more superior source of protein.
It’s important to note that all nutrients come from the sun and the soil. Other animals don’t make the essential amino acids. They all originate from plants and microbes. Even though plant-based protein is absorbed differently and most aren’t “complete” (apart from some sources including quinoa, amaranth and soy) Dr. John McDougall says it’s impossible to become amino acid–deficient if you’re consuming a healthy, unprocessed plant-based diet. He states: “It supplies all the protein, amino acids, essential fats, minerals, and vitamins (with the exception of vitamin B12) necessary for excellent health.“
The human body actually recycles proteins and maintains a pool of amino acids which can be used to complement dietary protein. Dr. Michael McGregor says: “90g of protein is dumped into the digestive system every day from our own body, to get broken back down and re-esembled, so the body can mix and match amino acids to whatever proportions we need, whatever we eat.” Therefore, as long as you are consuming enough of a variety of fresh foods there is no need to combine different plant proteins at each meal.
Assimilation and utilisation
Many people don’t realise that just because something contains a high amount of protein, it doesn’t mean we absorb, assimilate, and use all of it effectively. There are several key factors which need to be considered that influence the digestion of protein and how the body uses it. Prof. Dr. Franz-Ulrich Hartl from the Max Planck Institute of Biochemistry explains: “Proteins are chain-like molecules. In order to function properly, they must fold into complex three-dimensional shapes.” This is a physical process by which the protein achieves its natural functional state. But there are circumstances where this process fails.
In the book Molecular Biology of the Cell it explains that this process is called denaturing, whereby the natural interactions holding the folded chain together have been disrupted. Interestingly enough the protein has the potential to refold, or renature, into its original structure. Unfortunately, Prof. Dr. Franz-Ulrich Hartl explains that things can go wrong with this sophisticated system and misfolded proteins can begin accumulating. One main reason for this is that the protein is incorrectly constructed in the first place, which is caused by cooking food. Proteins are not lost during cooking, but overcooking and cooking at very high temperatures will denature proteins found in food.
This is particularly true in the case of animal products as they are generally cooked before being eaten. Upon heating muscle the connective tissue loses its native molecular shape or conformation. As the temperature increases, the more a protein starts to unfold. This study states that during cooking, an accumulation of oxidative damage occurs in proteins (by an increase in free radical production and an impairment of the antioxidant protection). The denatured proteins then form an aggregate by the strands sticking together. The modified structure of amino acids may induce unpredictable biological effects.
Scientist Tzer‐Yang Yu states: “Even if digestion is unaffected or improved through heat treatment, a modified peptide may not be utilised in the same way as the unmodified one.
“The cooking process restructures and denatures the protein in the meat. The amino acids are still there per se, but have lost their characteristic biological activity. This is a fancy way of saying it is broken, and therefore only 20-30% of the protein is actually available to the body. (This is what conventional diabetics overlook and is the main reason we are told to consume far more protein than is necessary).”
– Essentials to Human Anatomy & Physiology – Elaine N. Marieb
Fruits, vegetables, nuts and seeds do not need to be cooked, therefore the amino acids stay structurally correct and the body can absorb and utilise all of the amino acids properly. Obviously you can eat raw meat if you choose, but then you’re exposing yourself to a whole host of other problems i.e. parasites and contamination.
The build up of mis-folded proteins can clump together and accumulate inside or around cells, which is toxic to the cell and impairs its function. This accumulation process leads to an imbalance in the cellular protein homeostasis and eventually to cell death. Cell death caused by the build-up of toxic aggregates is said to be a key feature of many degenerative disorders, including Huntington’s and Alzheimer’s diseases.
The largest nutritional study ever done, involving real people in real life, shows that all degenerative diseases (cancer, heart disease, diabetes, arthritis etc.) increase when you eat an amount of animal protein over 10%. The following conditions can also occur as an effect of eating animal protein:
- Animal protein intake has a profound effect on normal kidney function, inducing what’s called hyper-filtration, increasing the workload of the kidney. It causes an inflammatory response in the body whereas plant protein does not. Continual animal protein intake forces the kidneys to call on its reserves, causing stress which leads to kidney scarring and dysfunction whereas plant protein does not have this effect.
- Animal protein contains cholesterol in a form that cannot be used by the body. Plant foods don’t contain any cholesterol. Your liver makes all the cholesterol you need, so you don’t need to eat foods that contain this type of fat. The Institute of Medicine did not set a tolerable upper limit for trans fat, saturated fat, and cholesterol because any intake level above 0% of energy increased LDL cholesterol concentration. In fact when you do consume it, the amount of cholesterol circulating in your blood increases, and so does your chance of experiencing blocked arteries and heart disease.
- The Journal of Nutrition stated: “The decrease of meat protein digestibility by cooking processes may not only reduce the bioavailability of indispensable amino acids, but also increase the quantity of protein that reaches the large intestine. Proteins that escape digestion are fermented by the colon microbiota and release potentially harmful metabolites, such as hydrogen disulfide, ammonia, and phenolic compounds. These metabolites are believed to have deleterious effects on colon mucosa.“
- Animal protein is used at a more rapid pace by the body, increasing the levels of growth hormone, which is why many people consume it to increase their body size quickly. It’s important to note, however, that it also means growing cancer cells faster and speeding up ageing. Plants do not have the same effect because proteins in plants have a different composition, and don’t stimulate growth hormones as efficiently as meat proteins.
- The World Health Organisation (WHO) has released a statement that proves there is a relationship between the consumption of red and processed meat and the risk of developing colorectal, pancreatic and prostate cancer.
- The way you cook meat also relates to your risk of cancer. High-temperature grilling creates potentially cancer-causing compounds in meat, including polycyclic aromatic hydrocarbons and heterocyclic amines.
The Medical Journal of Australia states: “In comparison to protein foods of animal origin, most plant protein sources are lower in saturated fat, free of cholesterol and haem iron, higher in fibre, and are good sources of antioxidants and phytochemicals, all of which may contribute to a reduced disease risk. The consumption of plant protein rather than animal protein may play a role in weight management and reducing chronic disease risk.“
This study shows that a diet based predominantly or exclusively on plant food provides a preventive effect against cardiovascular disease as well as a retardation of cancer development. A sufficient consumption of plant proteins has the protective effects against chronic degenerative diseases.
I believe the language used to describe animal protein is misleading and oftentimes causes people to believe that better “quality” equals better health. Perhaps this situation is playing a role in the disease epidemic of our day?
Whatever diet you choose, I would always recommend eating an abundance of raw plant whole foods as they allow the body to make maximum use of all amino acids without the accompanying negative effects of cooked food. Plus they provide a beautiful collection of vitamins, minerals, water, phytonutrients, fibre and antioxidants which help us live a long, happy and healthy life.
Get your protein from plants when possible. Eating legumes (beans and peas), nuts, seeds, whole grains, and other plant-based sources of protein is a win for your health and the health of the planet. For a healthy diet focus on a low intake of protein from meat and higher intake from plant sources. Ensure though that you prepare nuts, seeds, and grains correctly to allow for optimum absorption of nutrients.
My intention for this article is to highlight the key differences between plant and animal sources, and acknowledge the potential health concerns associated with a diet of protein consumed primarily from animal sources. I want to portray the truth to enable you to make an educated decision when it comes to what you put into your body.