Jennifer Hanes MS, RDN, LD
People often discuss protein, typically concerning muscle growth and maintenance. But rarely do you see good recommendations of how much you actually need, what happens if you eat too much, or what conditions change how much you should be eating.
And what does protein do other than contribute to growth?
What is protein?
Before we discuss the function of protein in our bodies, we should make sure everyone is clear on what a protein actually is.
Proteins are not individual compounds. Instead, they are actually intricate chains of amino acids that are folded into a big jumble based on the chemical bonds that form between those amino acids.
A protein’s function is entirely based on the structure that it forms. An incorrect amino acid in the chain alters the structure and, thus, the function of the protein.
For example, just a single amino acid substitution in the hemoglobin in our red blood cells creates a severe structural change that causes sickle cell anemia, which in turn results in poor oxygenation and severe whole-body pain in the afflicted person!
Furthermore, our bodies don’t use proteins as we eat them. Instead, cooking and digestion denature the protein, allowing our bodies to break apart each protein into individual amino acids and then create the protein structures that we need!
Think of the protein in our food as the base needed to create structures for a gajillion different functions in our body.
Functions of Protein
Out of all the nutrients we will discuss in this series, protein probably has the most functions in our bodies. There’s probably a protein function discussed below that you haven’t thought of before.
Immune system
Antibodies are made of proteins.
When we have an infection, our immune systems send antibodies to fight the virus or bacteria. These antibodies are like memory cells for fighting infectious diseases.
Enzymes
Every chemical reaction that occurs in our bodies occurs with enzymes.
If you think really hard back to high school chemistry class, you may remember what a catalyst is.
An enzyme is a protein-based catalyst that enables important reactions to occur much faster than they would otherwise. Co-enzymes are also involved in many cases.
Enzymes not only drive our entire metabolism but also “read” and express our DNA.
Messenger Proteins
Many, but not all, of our hormones are actually proteins. These hormones are responsible for communication between cells, tissues, and organs.
Examples include human growth hormone, thyroxine (thyroid hormone), and melatonin (sleep hormone).
Structure
Some proteins provide structure for our bodies, as well as allow us to move. This does include our muscles, but also proteins collagen and keratin, found under our skin and in our skin and nails.
Transport and Storage
Some proteins are responsible for carrying small molecules and atoms throughout our bodies.
Examples include hemoglobin and ferritin, used to transport oxygen and iron, respectively.
pH Buffering
Maintaining a constant pH is extremely important. One of the methods of maintaining your blood pH between 7.35 and 7.45 is to use proteins as a buffer.
Fluid Balance
Albumin and globulin are proteins that are normally in your blood.
When we don’t eat enough protein for a long time, these protein levels decrease, leading to to “leaking” of fluid between the cells instead of remaining in the bloodstream.
More typically, albumin decreases when there is a large amount of inflammation in your body, as a result of acute illness or injury.
Provides Energy
When you aren’t eating enough, your body can actually break down storage proteins (muscle) to provide energy to your body.
This is one of the reasons that extreme calorie restriction doesn’t lead to sustainable weight loss. Instead, you lose muscle mass as it converts to fat storage instead.
Recommended intake
This is a very hard question to answer and one that should be answered through a consultation with a dietitian. Many, many things can alter how much protein you should be eating.
For a healthy person, current recommendations are 0.8-1 gram of protein per kg of body weight.
Take your weight, divide it by 2.2, then multiply it by 0.8.
So a person that weighs 150 lbs should aim for 55-68 grams of protein per day.
But what if that person isn’t healthy? Certain kidney conditions require you to take in less protein than usual. However, people whose kidneys have completely failed and require dialysis may need more than double that amount of protein.
Illness, metabolic stress, growth (think pregnancy and children or strength training), obesity, weight loss (intended and unintended), and many more conditions can increase your protein needs. All of these things are more than we can really get into in a general nutrition article on the internet.
If you have concerns, consider making an appointment with a dietitian near you.
Protein Intake Timing
In addition to how much you need, you should also pay attention to how you eat it. Your body only efficiently utilizes about 25-30 g of protein at any given meal (or about a 2-hour span).
So your meat-eating friends that sit down to a huge steak dinner may be getting enough grams of protein in but aren’t utilizing it very well. After the body absorbs approximately 25-35 grams of protein, it excretes the excess as waste through urine, feces, or respiration or converts it to fat storage.
But at the same time, they are absorbing the saturated fat and heme iron, both of which can potentially lead to heart disease when eaten in excess.
Aim to eat protein at each meal and snack. This will keep you fuller and will pack a bigger protein punch. That means your 3 pm snack of chips from the vending machine should be switched to Greek yogurt and grapes or a handful of almonds.
Additionally, as you age, you absorb less protein per meal. There’s a lot of nuance here. The main takeaway is that you should include protein every time you eat.
Protein Sources
Protein is present in a lot of foods!
Omnivores tend to find their protein easily in meat.
Vegetarians can get protein from dairy, eggs, beans, legumes, nuts, seeds, and seitan. Obviously, a vegan diet avoids dairy and eggs. I would strongly suggest that vegetarians avoid relying too heavily on dairy for protein and venture out into some of the vegan choices.
Soy products such as tofu, tempeh, and edamame have multiple health benefits from phytochemicals. Tempeh has the added benefit of being fermented, so it can provide (a few) probiotics for your gut.
Nuts and seeds are nutrient powerhouses, including peanuts and peanut butter. In addition to protein, they contain healthy fats, fiber, and magnesium. Just make sure to keep your portion size in check!
Misconceptions of Plant-Based Protein Sources
There are a couple of misconceptions regarding protein in a vegetarian diet.
The first is the easiest to debunk; You can’t get enough protein without meat.
There is rarely a person who needs so much protein that they can’t get enough without meat. There are plenty of vegetarian protein sources, and even omitting dairy and eggs doesn’t automatically prevent you from getting enough.
In fact, conditions that significantly increase how much protein you need will often require protein supplementation, even in omnivores. This can occur in end-stage kidney and liver disease or in severe injuries such as 3rd-degree burns.
The second misconception of protein in vegetarians involves incomplete proteins. While it is true that most plant-based protein sources are incomplete proteins, it is not true that you need to worry about this.
An incomplete protein is one that has lower levels of 1 or more of the nine essential amino acids that are needed for all of your protein-based functions.
An essential amino acid is one that you cannot produce through your own metabolism, so you must get it from your food.
With the exception of soy and quinoa, plant-based proteins tend to be incomplete.
In the past, vegetarians were encouraged to eat “complementary proteins.” This is essentially pairing foods so that in combination, you form a complete protein; for example, rice and beans
However, we now know that you don’t have to do this on a meal-to-meal basis. As long as you are getting protein from varied sources, you’ll be fine.
Supplements and Fortified Foods
Protein supplements and foods fortified with protein can help you get enough protein, particularly when you are strength training or have a low appetite for whatever reason.
Whey protein supplements are the most quickly and completely absorbed. However, some whey supplements may still contain lactose, causing problems for those with lactose intolerance. Others report significant constipation from whey supplements.
Other vegetarian options include egg white and casein protein supplements. Vegan options are less absorbable and include pea, hemp, brown rice, and chia proteins. The best option is to pick a product that has a blend of vegan protein options.
Ready-to-drink protein shakes are the easiest options. These are easy to find and come in a variety of flavors, price points, and targeted nutrition needs.
Vegetarian and vegan protein powders are another option. You can buy these in most grocery or health food stores, and they also come in a variety of flavors.
For the most part, these are meant for muscle growth, so you won’t see options specific for kidney disease, diabetes, and other conditions as readily as you would a ready-to-drink shake.
However, you can get unflavored options that are great for adding to foods you’re already eating, such as soups, stews, smoothies, and yogurt.
Foods that are fortified with protein are a bit less common but do exist. Common brands include Kodiak and Premier and are usually some type of carb source with whey protein added, such as oatmeal, pancakes/waffles, and muffins.
Symptoms of protein deficiency
Protein deficiency is not common in most developed countries. When it occurs, it typically is the result of not eating enough, such as the “carbotarian,” a vegetarian that avoids meat, but doesn’t attempt to make up the protein difference.
We also see protein deficiency in the homeless population, and I actually see quite a bit of protein deficiency in my work in a psychiatric hospital. Depression often causes a complete lack of appetite resulting in muscle wasting.
If a mild protein deficiency exists, the body will turn to its stores, mainly muscles and bones. The hair may become thin and dull, and the nails become brittle. Bones become more prone to fractures. Infections become more frequent.
Mild deficiency tends to increase your appetite, particularly for savory foods, potentially resulting in weight gain. This is partly why many personal trainers will recommend increasing protein intake. This is actually good advice!
As protein becomes more scarce, muscle wasting and weight loss become very obvious, and some patients will experience fluid loss in the abdomen or lower extremities. Appetite becomes suppressed.
Conditions that increase protein needs
There are conditions that increase your protein needs, as discussed above.
A condition known as protein-losing enteropathy is a GI disease that causes a massive loss of protein through the GI tract. Other GI disorders can cause problems metabolizing, absorbing, or utilizing protein that is ingested.
Liver cirrhosis and kidney dialysis are major sources of protein loss in afflicted patients, and if the diet does not replace the lost protein adequately, those patients will experience symptoms of protein deficiency.
Also, severe injury and illness can significantly increase protein needs for a variety of reasons. Any person experiencing these conditions should discuss their nutrition needs with a dietitian who is familiar with their medical history and lifestyle.
Treatment for protein deficiency
For most cases of mild protein deficiency, altering the diet to increase protein intake is enough. Take care when increasing protein; choose options low in saturated fat, and be sure to drink more water than you were before.
However, in cases where the patient is critically ill, the underlying cause of protein deficiency must first be addressed. Otherwise, increasing protein will simply lead to increased fat tissue, not protein stores.
These patients are generally in the hospital and are being closely monitored by dietitians, nurses, doctors, and physical therapists.
When protein deficiency is caused by starvation, whether due to an eating disorder or through lack of access to food, a whole other set of issues comes up.
These patients should also be monitored closely for signs of illness from serious electrolyte imbalances that can occur if they suddenly start eating again.
A dietitian should be a part of the care team for these patients.
Symptoms of protein toxicity
Protein does not have any associated toxicity. However, we should aim for adequate intake, not too much, for a couple of reasons.
First, increasing protein oftentimes means increasing saturated fat, particularly in our omnivorous friends, which can lead to various inflammatory diseases such as heart disease and diabetes.
Second, if we are eating way more protein than we need, we are most likely displacing other foods that should be in our diet. Again, I feel like this is more common in those that eat meat.
But a vegetarian who is getting full off an excess of Greek yogurt, cheese, eggs, and soy may not be eating healthy amounts of fruits and vegetables.
Should I take a supplement?
In general, no. If your diet lacks adequate protein, simply increase your intake of protein-rich foods. Again, vary your protein sources and spread them out to ensure you get the overall nutrition you need.
Even those trying to put on muscle can easily reach their protein needs by adding 8oz of plain Greek yogurt (23 g protein) with some fruit after their workout.
If you’ve experienced rapid weight loss and muscle wasting or have specific protein-losing conditions, then you may warrant a protein supplement. The same applies to people with high needs and poor appetite, such as cancer patients or older adults.
There are several good products available, even ones tailored to your specific needs. If you have any of these conditions, you should see a dietitian regularly.
Any concern for the omnivores?
Not really, concerning protein. However, encourage your omnivorous buddies to participate in meatless Mondays or other such reductions in meat to reduce their saturated fat intake and increase their intake of fiber and phytochemicals.
I would encourage them (if they asked) to include meat as an accompaniment to their meal, not the star of the show.
Those who are semi-vegetarian or flexitarian might be at risk if they simply cut out meat and increase vegetables. Encourage them to replace meat with other protein sources.
Animal-based proteins include eggs and dairy, such as yogurt, cheese, milk, and kefir.
Plant-based protein sources include nuts and seeds (including chia seeds, hemp seeds, peanuts, cashews, almonds, etc, beans and lentils, soy (tofu, edamame, tempeh), and seitan.
Whole grain products have more protein than their refined grain counterparts. Vegetables do have a small bit of protein, but should not be considered protein sources. (yes, even broccoli).
Here’s an example of 100 g of protein, all from vegetarian sources:
Breakfast: 8 oz 2% Greek yogurt with protein granola
Snack: 1 apple with 2 Tbsp peanut butter
Lunch: Side salad (1 cup spinach, 2 Tbsp shredded cheese, 2 Tbsp sunflower seeds, 1 oz dressing) and tofu sandwich (2 slices whole grain bread, 1 serving super-firm tofu, sliced red onion, mashed avocado).
Snack: 1 stick pepper jack cheese, grapes
Dinner: Broccoli casserole (quinoa, cheese sauce {cheddar cheese, milk}, broccoli)
Snack: 1 oz almonds, blueberries
This day comes to approximately 2200 kcal and 103 g protein.
In short, yes. Read more about whey protein.
I guess this depends on what you mean by “work.”
They do contain protein, often from a few different sources, but sometimes just one. They are generally, but not always, lower in protein than whey or casein versions.
But they can be effective in making up a protein deficit or helping you with muscle recovery after strength training.
Absolutely! Protein breaks down into amino acids during digestion and then utilized by our body as it needs it.
This process occurs wherever the protein comes from; it does not matter if the protein is animal or plant-based.
Jennifer Hanes MS, RDN, LD is a registered dietitian, mom, wife, and vegetarian in North Texas. She has dedicated Dietitian Jenn to be a source of information, ideas, and inspiration for people like her, vegetarians that live with people with different dietary beliefs and/or needs in a multivore household.