Why The Type of Protein You Eat Matters: All You Need to Know about Protein Digestibility & Absorption
Protein digestibility is not talked about enough.
When I first heard about protein digestibility, so many things clicked and started making sense about my health and why I was struggling to see improvement.
I was vegetarian and vegan for 5 years and knew that I needed to be educated about the proper combining of proteins to make sure I was getting all the essential amino acids. I made sure I did my own research and saw my naturopath regularly to monitor my iron and vitamin B12.
All the books I read (and I’m an avid reader!) and movies I watched had the same message “you can get all the protein you need from plant foods”.
Not once did I ever hear the term protein digestibility or protein absorption.
It wasn’t until I studied nutrition that I started hearing this term and reading more into it. The more I learned about this, the more passionate I became about teaching people the differences in various protein containing foods.
The reality is that that animal-based proteins are much easier for your body to absorb than plant based proteins.
Now I’m not saying you can’t get all the protein you need from plant foods or shouldn’t be vegetarian, I just want you to be aware and understand the entire picture when it comes to protein consumption so that you’re able to make educated decisions about which types of food you’re eating.
Every body is different with different needs throughout their life time and it’s important to honour what your body needs currently. I felt great being vegetarian for 4 years but when my digestive issues started it wasn’t working for me anymore.
If you know anyone with Irritable Bowel Syndrome or Small Intestinal Bacterial overgrowth, you’ll know that FODMAP rich foods like lentils and beans are super hard to digest, resulting in uncomfortable digestive symptoms. I switched my diet based on a health condition that I don’t think I could have overcome without that change.
My goal in writing this blog is to ensure you have a solid understanding of protein and the factors that affect it’s digestibility as it plays such a critical role in your overall health.
Protein Basics
Before we dive into protein digestibility, let’s cover the basics so we’re all on the same page.
Protein is made up of amino acids which are the building blocks of protein. Different structures and combinations of these amino acids make up different proteins in the body like hormones and neurotransmitters (brain chemicals) and many more.
There are 20 amino acids needed make all the proteins in the human body. 9 of these are essential. Essential means that you must get them through the food you eat as the body cannot make them. The non-essential amino acids can be made by the body using the essential amino acids1 so it’s not as important to make sure you’re eating these.
Another term you may have heard before is complete and incomplete proteins. A complete protein means that all 9 essential amino acids can be found within that protein source. You generally eat complete proteins in the form of animal protein, with the exception of soy2. Therefore, an incomplete protein does not contain all 9 essential amino acids.
The Canadian government suggests adult females and males get 0.80g of protein per kg of body weight3 a day so if you were a female weighing 150lbs this would look like 54g of protein in a day.
The thing to remember with this RDA’s is that they’re generally designed to provide a minimum amount required to prevent deficiency disease. They don’t take into account your exercise intensity or duration, if your job is physically demanding, if you’re chronically stressed or if you have a disease or illness (which protein is needed to recover from). It’s important to aim for a higher daily amount if your lifestyle contains any of the above.
The 3 Major Functions of Protein in Your Body
Protein plays a wide range of functions in the body; some may be more familiar to you than others. When protein is deficient, you may start seeing signs or symptoms of deficiency in the below areas. It’s important to address these because nutritional deficiencies left unaddressed can turn into illness or disease.
1. Growth, maintenance, healing & repair (muscle growth, hair, skin, nails, gut lining):
In order for our bodies to build and repair, there must be a constant supply of amino acids to do this, which means eating protein at every meal!
The quality of your hair, skin and nails are a great way to tell if your protein deficient. Your body prioritizes using protein for other more critical functions in the body. If there’s enough protein left then it goes to your hair, skin and nails.
2. Energy (exercise & fatigue):
Protein is a source of energy. The key to remember here is to actually eat enough!...and ensure your meals are balanced with protein, healthy fats, fiber and non-processed carbs.
With our fast-paced world so many people skip meals or just grab a couple snack foods for lunch while they work at their desk. Without fuel, your brain and body isn’t going to be able to run optimally. Aim for a protein source at every meal or if your vegetarian/vegan, 2-3 plant based proteins per meal.
Low energy and fatigue is something so many people struggle with today and often switching around what you’re eating earlier in the day can resolve this. Swap out the high carb breakfast like cereal, oatmeal, toast with nut butter for high protein foods like eggs, chicken, yogurt and/or kefir. The more protein and healthy fat you have first thing in the morning, the more energy and less sugar or hunger cravings you’ll have later in the day.
3. Messengers (signaling molecules):
The body uses the protein you eat and creates various messenger molecules from it…so if you’re protein deficient, the below areas may start to suffer.
Enzymes (digestive capability): your body makes enzymes from protein, which are catalysts for chemical reactions. They help join together or separate a variety of different substances at a much quicker pace then what you could do without them. Many people are familiar with supplemental digestive enzymes which help break your food down for better nutrient absorption.
Hormones (thyroid, blood sugar regulation): Hormones are chemical messengers that support communication between your cells, tissues and organs. Protein hormones include insulin, glucagon and thyroid hormones.
Neurotransmitters (anxiety, depression): In order for your nervous system to function properly, it needs a number of amino acids from protein foods. Protein deficient diets can lead to neurotransmitter imbalance, significantly impacting mental health including anxiety and depression⁴.
Antibodies (immune support): protein plays a critical role in immunity. Antibodies are proteins formed as a response to foreign proteins that enter the body like viruses, bacteria, pollens or food proteins. The body produces a specific antibody to bind with the foreign antigen and inactivate it, playing an important role in maintaining health.
Hemoglobin (blood oxygen capacity): this is an iron bearing protein that is a key component of your red blood cells. It helps with the transfer of oxygen from the lungs to the tissues in the body.
Acid-alkaline balance (water regulation): The body constantly produces acids and bases from chemical reactions. Proteins act as a buffer, normalizing the acid-alkaline balance in the body, maintaining the body’s pH around 7.4. This is important because a slight change in pH could result in extreme damage or death.
Protein Deficiency Symptoms to Watch out For: feeling weak or hungry, brittle nails, hair loss or breakage, poor immune system function, mood changes, hormone imbalance (ie. PMS, menstrual issues), inability to build muscle or stiff joints & bone fractures.
Brittle nails, hair and skin are a sign of protein deficiency
You Are What your Absorb, Not What you Eat!
That’s right, just because you eat a cup of lentils doesn’t mean you’re getting the protein specified on the package label. This can be misleading to many people and is important to note especially if you’re vegetarian as you may not be absorbing the amount of protein you think you are.
There are 3 factors that influence the actual amount of protein you absorb when eating a food, including:
Protein Processing:
Processing or altering of protein structure also changes the digestibility of that protein⁵. This could be your cooking method or processing technique a company used for something you purchased in a package like lentil pasta.
As an example, dried whole soybeans have a digestibility score of 53. After roasting them at 110-115ᵒC, the digestibility score increaes to 72. The heating (processing technique) significantly increases the digestibility score, making the roasted form a better source for eating⁵.
Antinutrients:
This refers to other plant compounds (besides protein) that interfere with your body’s ability to absorb nutrients (either protein, vitamins or minerals) from a particular food and are generally found in plant foods. Some more common anti-nutrients include lectins, goitrogens, phytates, oxalates, tannins. Some studies estimate that the protein digestibility ratings may over-estimate protein digestibility without taking anti-nutrients into consideration⁶⁷.
Digestibility:
Protein digestibility refers to the proportion of protein eaten that is broken down into amino acids and absorbed in the small intestine.
In order to understand how much protein people are actually absorbing from a food, a scoring system was developed to rate the digestibility of different proteins called The Digestible Indispensable Amino Acid Score.
Most animal protein (chicken, turkey, fish, beef, eggs, dairy) all score 99 or higher, indicating excellent digestibility (except for ground beef which fell just below 100). Plant range between moderate to low digestibility. This is because your body has to do more work to actually breakdown all the fiber (from the plant walls) to get to the protein before it can start breaking that protein down. Animal protein has no fiber, which makes it much easier to breakdown the protein into amino acids.
The below image shows a a list of the main protein sources grouped by digestibility⁵:
Digestibility of Common Protein Sources
If you take almonds for example, in 1 oz there’s 6 grams of protein with only a 40% digestibility so the amount you thought you were getting is lower.
If you are plant based, it’s important to take the digestibility of protein into consideration when planning your meals. This may mean focusing on more soy and when eating meals, try to get 2-3 higher plant protein sources. A good example may be a bowl with lentils, tofu and hemp seeds with whatever vegetables you’d like to add.
Let’s Not Forget Your Own Digestive Capability
Another key piece to this absorption puzzle is how well your digestion is actually working. This is something that’s not taken into consideration in the rating systems but as a nutritionist this is something I’m working with clients on all the time.
Stomach acid is the first main chemical step in digestion of proteins (after chewing), which breaks the protein you eat down into amino acids.
Many people actually have too little stomach acid (and are likely not aware of it!) which ultimately decreases your ability to use the protein you’re eating. You could eat all the protein you like but if you’re not absorbing it, your body is still starving of this critical nutrient and all the areas listed in the Protein Function section above will suffer. If you want to learn more about how your digestive system works my blog post “Gut Health 101: Why is Gut Health so Important” covers this in detail.
Factors that can negatively impact stomach acid levels and protein absorption include⁸:
Use of Antacids: blocking stomach acid exacerbates low stomach acid even more
Chronic Stress: reduces your ability to produce stomach acid and digestive juices
Poor Diet: a diet high in processed foods, refined sugar & grains, trans fats, chemicals (pesticides) and low fiber result in inflammation, increasing stress which then impacts ability to produce stomach acid
Eating too Quickly: eating too fast without enough chewing creates stress in the body, reducing ability to make sufficient stomach acid and can lead to indigestion
Anti-biotics & Painkillers (Tylenol, Advil etc.): they disturb the microbe ecosystem in the gut and wear down stomach lining, impacting the ability to produce stomach acid
Eating Foods you’re Sensitive to: this is a tough one because many people either aren’t aware of the foods they’re sensitive to or choose to ignore the symptoms their body is giving them (i.e. Digestive, skin, mood issues). Eating foods you’re sensitive too is a stressor to the body, impacting the ability to produce stomach acid.
If you’re thinking “okay I definitely have some of that going on in my life! Do I have low stomach acid?”, here are some common symptoms you could experience to indicate if you have low stomach acid:
Bloating
Gas and burping immediately after eating
Heartburn
Iron deficiency
Indigestion
Skin issues: dry skin, acne
Fatigue
Weak, peeling or cracked finger nails
Hair loss in women
You will see so many positive changes in all areas of your body after working on rebuilding and improving your stomach acid and digestive organs. This was a game changer for me! Many people who go vegetarian because they don’t feel great after eating meat may have this as an underlying issue.
If you’d like to learn more about how to do this or have questions about this process would look like, I’d be happy to help! You can book a free discovery call below.
So What Type of Protein Should I be Eating?
This obviously depends on your food preferences and ideologies. The best answer, regardless of if you eat meat or not is going to be a variety of protein sources. This is especially important if you’re vegetarian or vegan because you will need a variety of complimentary sources to ensure you’re getting all essential amino acids.
Variety is not just about protein though, it’s about all the other nutrients like vitamins, minerals, fiber and phytochemicals (plant nutrients) that we get when we eat that proteins source. The greater the diversity, the healthier your body will be because you’re eating a greater range of nutrients that your body needs for various different functions.
If we eat the same meals for breakfast every day or only rotate between a few lunch and dinner options each week, you’re only benefitting from the nutrients in that one type of protein source. Your body will benefit the most by mixing and matching both plant and animal sources.
For example, eggs are also a good protein source and also have choline (supports your brain), vitamin D, vitamin A and many other vitamins and minerals. Lentils on the other hand are high in iron (which eggs are not), phosphorus, folate and also have prebiotic fibers to feed the good bacteria in your gut.
It can be difficult to figure out and know exactly how much protein you need based on what’s going on in your life and what type works best for your body. For example, if you have IBS, plant-based proteins are probably going to make you feel a whole lot worse and animal protein may be the best choice for you!
If you feel like you need a little support to figure out what nutritional strategy works best for your lifestyle needs, I’d be happy to help! Click below to book a free discovery call.
During the discovery call I get to know a little more about you and discuss a strategy to help you achieve your health and nutrition goals!
Sources:
1 https://www.ncbi.nlm.nih.gov/books/NBK557845/
2 https://pubmed.ncbi.nlm.nih.gov/19145965/
4 https://www.ncbi.nlm.nih.gov/books/NBK224629/
5 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8912699/#B79-nutrients-14-00947
7 https://pubmed.ncbi.nlm.nih.gov/9164998/
8 Guide to Nutritional Symptomatology, 1st Edition. Canadian School of Natural Nutrition
By Krista Znebel, R.H.N.©
Feb. 14, 2024