What Does Protein Do?

Written by Andrew Brewer. ⚕️Reviewed and fact checked by Dr. Kimberly Langdon.


Did you know that protein is found in virtually every part of your body?  In fact, without it, you would have no body.  Proteins are the building blocks of skin, bone, muscle, hair, and organ tissues.  There are at least 10,000 different types of protein in the human body!

So it’s no wonder that protein is a big deal in the world of dieting and bodybuilding.  There are dozens of protein supplements on the market, and each promises to help you fulfill your fitness potential while optimizing your health.  But protein intake is also a subject of major contention!

Here are some of the counteracting claims you may have read about protein:

  • You can never get too much protein.
  • If you’re an athlete, you need way more protein than the average person in order to bulk out.
  • Too much protein can damage your kidneys and bones and cause long-term health problems.

It’s hard to know what to believe when you read such vastly differing claims!  Is protein really dangerous to your bones and kidneys?  Can you get too much?  Do most people get too little?  Are the high doses taken by athletes really safe?There is so much misinformation out there, but if you do your homework, you will find that there are answers.  In fact, we’ve gone ahead and done the research for you.  Let’s discover the truth about protein by taking a look at the science!

Key Takeaways

  • Protein is a vital nutrient that plays a crucial role in building and maintaining muscle, bone, hair, skin, and organ tissues, as well as DNA replication, enzyme production, hormone regulation, and immune function.
  • There are three types of amino acids: essential, non-essential, and conditional. While your body can manufacture non-essential amino acids, it still needs to obtain them from your diet, along with essential amino acids.
  • Complete proteins contain all eight essential amino acids your body needs, while incomplete proteins lack one or more essential amino acids. Vegetarian sources tend to supply incomplete proteins, while many complete proteins are derived from animal sources.
  • Protein supplements can be beneficial for vegetarians who need essential amino acids their diet is failing to supply and for meat-eaters who want to avoid a diet too high in saturated fat.
  • While there are some concerns about consuming too much protein, for the most part, protein is safe and necessary for optimal health. The key is to find a balance and get the protein you need through a healthy, balanced diet.

What Is Protein?

We don’t want to get too deep into biochemistry, but it’s helpful to have at least a basic understanding of what protein actually is.  Proteins are large biomolecules sometimes referred to as “macromolecules.”  Each is made up of one or more amino acid chains.  Each of the 10,000+ types of protein found in your body fulfills a different role which is vital to your health.

There are three different types of amino acids:

  • Essential:  These are amino acids which your body cannot manufacture on its own.  You must get these amino acids through your diet!
  • Non-essential:  These are amino acids which your body is able to replicate.   Note however that non-essential acids are made out of essential amino acids or are manufactured when your body is breaking down protein.  So you technically need to get non-essential amino acids through diet too.
  • Conditional:  These are amino acids your body needs when under stress (for example, while recovering from an infection or injury).

Amino acids are foundational to life itself, and eating protein allows you to get the amino acids you need!

Why Is Protein Important?

Here are just a few of the vital functions of proteins in your body!

  • Proteins are the building blocks for muscle, bone, hair, skin, and pretty much everything else in your body.  Ignoring water, 75% of your body weight is made up of protein!  Without it, you would quite literally not exist.  This is also why proteins are critical for wound healing.
  • Proteins are necessary for DNA replication.
  • Proteins make up enzymes.  Enzymes fulfill a variety of key functions in your body, including helping your digestive tract break down food and extract nutrition.  That means if you are not getting enough protein, you may also have a hard time getting the other nutrition you need.
  • Another important type of molecule is hemoglobin.  Hemoglobin is found in your red blood cells, and transports oxygen from your lungs to tissues throughout your body.  Hemoglobin also carries carbon dioxide back to your lungs.  And guess what hemoglobin is made of?  Four different types of protein molecules!
  • Protein is a vital nutrient when it comes to the production and regulation of hormones.  Hormones regulate many of your other vital processes, so having a proper balance of hormones is critical if you want to feel and function at your best.
  • You need protein in order for your immune function to work at its optimum.  When you do not get enough protein, you may be more susceptible to illness.  When you get the protein you need, you are less likely to get sick, and when you do, you will recover more quickly.

Types of Protein


It would be impossible to get into each of the 10,000 different types of protein in your body in-depth, but one thing we can talk about are the common types of protein which you can purchase as supplements for dieting and bodybuilding.

First off, there are two main types of protein in diet:

  • Complete proteins:  These are proteins which contain all eight of the essential amino acids your body needs from diet.
  • Incomplete proteins:  These proteins lack one or more essential amino acids.  These are not as nutritious as complete proteins.

One of the challenges faced by vegans and vegetarians is the fact that many complete proteins are derived primarily from animal sources.  Vegetarian sources on the other hand such as fruits, veggies, nuts, and grains tend to supply incomplete proteins.

Believe it or not, complete proteins do come with a downside.  While they give you the essential amino acids you need to function at your best, they also tend to include a lot of saturated fat!  So if you eat a lot of protein-rich meats, you are also eating a diet high in saturated fats.  These are both reasons why vegetarians and meat-eaters alike often turn to protein supplements to get what they need.  For vegetarians, it is a matter of getting essential amino acids their diet is failing to supply.  For meat-eaters, it is a question of avoiding a diet too high in saturated fat.

If you’re shopping for a protein supplement for the first time, it is easy to get confused because there are a number of different types to choose from.  Each has its advantages and disadvantages and its own specific uses.  Some of the common types of protein powders include:

  • Whey concentrate.  This is one of the most popular types of protein supplements on the market, and is great for a variety of purposes.  Whey concentrate is taken before and after exercising by bodybuilders, and may also be used to by dieters as a snack between meals in order to feel full.  Its low cost makes it an excellent choice for protein newbies.  The downside?  Some people report it makes them feel bloated and gassy.
  • Whey isolates.  You’ll pay a premium for this type of protein supplement, but the upside is that your body will absorb it quickly.  This makes it great for working out.  Whey isolates also tend to be low in carbs and sugars, which makes them ideal for those on a weight loss diet.
  • Casein protein.  Sometimes what you need is the opposite of quick absorption.  If you want a protein your body will take hours to digest, casein is what you’re in the market for.  This type of protein is perfect for maintaining satiety.  Use it while you’re on a diet to curb your cravings.
  • Soy protein.  Need to stay away from meat-based protein sources?  Soy protein is your perfect vegan alternative.  As a bonus, it is chock-full of arginine, glutamine, and BCAAs.  These are all nutrients which are awesome for bodybuilding!
  • Hydrolysate protein.  If you want something easy on your digestive tract which is going to provide you with amazing anabolic benefits for your workouts, it is hard to beat hydrolysate protein.  Just be warned, the price tag is hefty!
  • Protein bars.  While a lot of the protein supplements you find are powders, you will also find plenty of protein bars in most health food stores.  These bars are designed as meal replacements, and may be a handy choice if you are in a rush and don’t have time to make a shake (though there are also ready-made protein shakes you can buy).  Just toss one in your bag and head out the door.  Just watch out for bars which contain additives you don’t need like excess sugars.

You should now feel pretty comfortable with your understanding of what protein is, why people take protein supplements, and what your options are as far as different types of protein powders you can use in your shakes.  Let’s move onto the next topic: How much protein should you actually be taking?

How Much Protein Do I Need?


First of all, I want to emphasize that there is no single optimum level of protein intake.  How much you need depends on you in large part.  You need to account for your age, sex, and weight as well as your needs.  Someone who is trying to lose weight will take a different amount than someone who is trying to gain weight, and so on.

Always start by asking yourself what you are trying to accomplish by taking protein:

  • Do you want to bulk out in the gym and actually put on weight?
  • Are you trying to lose or maintain weight?  Are you taking protein largely for purposes of satiety?
  • Are you trying to fill nutritional gaps in your diet?
  • Are you recovering from an injury?

Once you have that established, you will be able to figure out how much protein you need to achieve your goals.  You will not need as much protein just to meet your RDA as a vegan as you would if you were also trying to get ripped.

What is the Minimum Protein Intake?

According to the National Institute of Health, you need two or three servings of protein every day.  Some examples might include two to three ounces of cooked lean meat or fish, half a cup of baked beans, or an egg.

Daily Protein Intake Requirements for Men, Women, and Children

Talking in terms of grams, your needs depend largely on your age.  WebMD recommends:

  • Babies: 10 grams a day
  • Children: 19-34 grams a day
  • Teenage boys: 52 grams a day
  • Teenage girls: 46 grams a day
  • Adult men: 56 grams a day
  • Adult women: 46 grams a day
  • Pregnant or breastfeeding women: 71 grams a day

There are a couple of things that are important to note about this list.  First off, these are the intakes to aim for if you are just trying to meet your daily nutritional needs—not if you are attempting to gain or lose weight.  Secondly, these recommendations literally refer to grams of protein, not grams of food containing protein.

What Happens If You Have a Protein Intake Deficiency?

Thankfully an outright deficiency in protein is quite rare.  It is entirely possible however that you are not getting as much protein as you should, especially if you are a vegan or vegetarian and you haven’t taken steps yet to ensure that you are meeting your nutritional needs.  Here are some signs you could use more protein in our diet:

  • You’re always craving food, especially sugar. A diet rich in protein helps to maintain healthy, steady blood glucose levels.  If you are not getting enough carbs, you may find yourself turning to protein to try and make up for your energy deficit.  You may feel weak, tired, and foggy.
  • You have dull skin and hair. You might even be losing hair.  Both collagen and keratin, the main tissues that make up your skin and hair, are made out of protein.  If you are not getting enough protein, your body has a hard time manufacturing these tissues.
  • You are struggling to put on muscle mass in the gym, and may even be losing it. Nothing is worse than working out relentlessly week after week and looking in the mirror each day at depressing results.  Sure, the numbers on the scale are dropping, but not necessarily for the reasons you were hoping.
  • It is taking longer than you expect to heal from injuries, especially those you have sustained through working out.
  • In extreme and unlikely cases, you might experience more serious symptoms. If you were totally undernourished in terms of protein, you would develop a condition called protein energy malnutrition (PEM).  This condition results in anemia, skin inflammation, and a degenerating liver.  Another possible condition which could develop is called marasmus.  With marasmus, your muscles waste away and you become susceptible to illness.  Eventually, organ failure can result from protein deficiency.  Again, none of this is likely ever to happen to you unless you are starving, but it does highlight just how important protein is in your body!

If you are experiencing one or more of these symptoms and you know your diet is lacking in protein, then you could probably benefit from a protein supplement.  A protein shake now and again can help you get through your day with the energy you need, and can supply your body with the nutrition it needs to build healthy muscle, skin, and hair tissue.

How Much Protein is Too Much?

Can you get too much of a good thing?  According to Mayo Clinic, “a high-protein diet generally isn’t harmful.”  Researchers are still studying the long-term effects.  So far, scientists have concluded that there are a few potential health problems which can result from eating a high-protein diet or a long time period.

Side-effects of a high-protein diet over the long term may include:

  • Constipation resulting from insufficient fiber intake
  • Headache
  • Bad breath
  • Higher risk of heart disease associated with foods high in saturated fats
  • Kidney function damage in people who suffer from kidney disease

Take note: you only increase your risk of heart disease if you are using red meats and other protein sources which are high in saturated fats in order to boost your protein intake!  If you are sticking with protein shakes, you can avoid this so long as you shop for protein powders that are low in saturated fats!

Biggest Protein Myths

While we are on the topic of side-effects, this is a great time to go into some of the most persistent protein myths.  Like I mentioned earlier, there is a ton of misinformation out there.  I am going to tell you about research studies which reveal the truth about high-protein diets!

Can a High-Protein Diet Harm Kidney Function?

A moment ago I mentioned kidney damage.  Those two words cause panic in a lot of people, and understandably so.  That being said, unless you have kidney disease, there is really nothing for you to worry about with a high-protein diet.  As of right now, there are no research studies indicating that high-protein diets lead to kidney problems in people with healthy kidneys.  You only need to be concerned about this issue if you already have kidney disease.  See the studies here and here.

And actually, it is possible that a higher intake of protein could help to prevent kidney disease if you have healthy kidneys now!  Boosting your protein can help to reduce your blood pressure and prevent diabetes.  Both are risk factors in kidney disease.  See the research on diabetes here, and on blood pressure, here and here.

Does High Protein Cause Osteoporosis?

There is a persistent theory that eating a diet high in protein can leach calcium out of your bones, potentially leading to osteoporosis.  The thinking goes that a high-protein diet boosts the amount of acid in your body.  In an attempt to neutralize this acid, your body pulls calcium content out of your bones.

This actually does happen in the short term, but over the long term, the effects do not appear to persist.  In fact, the long-term effects of high (but not excessive) protein on your bones appear to be positive, just going off of the research.  This study for example actually concluded that increasing protein may result in improved bone health for older men and women!  Other scientific research also backs this up.

All of that said, there is still some disagreement in the scientific community on this, so the best advice would be to proceed with caution.  You can be pretty optimistic about eating a high-protein diet, but there is no reason to go overboard.

Do You Need a Huge Amount of Protein to Bulk Out?

Speaking of going overboard, another common myth relating to protein is that you need to eat a massive amount of it in order to get ripped—and that more is always better.  If you are increasing the amount of exercise you do, you probably do need more protein than you normally would eat.  But do you really need to eat double the RDA set by the Food and Nutrition Board?

Actually, if you are exercising the same amount as usual, adding more protein may not help at all if you add too much.  It may even be detrimental to your workout plan.  According to Gail Butterfield, PhD, RD, who works as the Director of Nutrition Studies at the Palo Alto Veterans’ Administration Medical Center, the extra caloric intake may mean you end up putting on extra muscle mass, but probably an equal amount of extra fat as well.

Worse, if you have a diet where protein is making up around 30% of your daily caloric intake, there can be a build up of ketones in your body.  These ketones are toxic and put a lot of stress on your kidneys.  In their desperation to flush out the toxins, your kidneys also flush out extra water, which can lead to dehydration.  While working out, this can be dangerous.  It may even lead to the loss of muscle mass as well as bone calcium (this may explain why so many people believe protein is directly responsible for bone and kidney problems).

So How Much Protein Do You Actually Need?


In truth, you may only need a small increase in your protein intake if you are trying to build muscle or experience other added benefits that come from eating extra protein.  There is no need to overdo it.  Use the guidelines for your age and sex to fill any nutritional gaps in your diet, and boost your intake just a little bit if you are doing mild to moderate exercise or trying to feel fuller throughout the day.

As just discussed, if 30% of your daily caloric intake is coming from protein, you are probably eating too much.  This is not a high-protein diet; it is (usually) an excessive protein diet.  The Food and Nutrition Board sets the RDA for protein at roughly 0.36 grams per pound of body weight.  This should amount to roughly 15% of your daily caloric intake.

Now, keep in mind that the RDA above is for a person whose activity levels are close to average.  If you work out a lot, you may need more than the average amount of protein, maybe even significantly more.  This study delves into the debate.  While there are many researchers who feel that protein intake should stay close to the RDA, many athletes protest based on their experiences.  The researchers in this study conclude, “[T]here is good rationale for recommending to athletes protein intakes that are higher than the RDA … Elevated protein consumption, as high as 1.8-2.0 g … may be advantageous in preventing lean mass loss during periods of energy restriction to promote fat loss.”

What is the bottom line?  Use your common sense when you decide how much protein to eat and supplement.  If you are only lightly or moderately active, keep your protein intake close to the RDA.  If on the other hand you are doing a lot of intense resistance training, maybe you should be doubling your protein intake.  Use caution, take careful notes on your progress, and adjust your diet accordingly.

When To Use Protein?

The type and amount of protein you take is important, but so is timing your intake so that you maximize your benefits.  When is the right time of day to take protein?

Generally speaking, you are going to want to take protein relatively evenly throughout the day, whether you are working out or not.  That way you can maintain relatively consistent nutrition throughout the day.  This will help to regulate your blood glucose and energy levels.

If you are exercising, you will want to make sure that you take extra protein after your workouts.  Try to do this within thirty minutes.  Doing so will ensure that you are fueling your muscles with the nutrition they need to repair damage from exercise.  This will aid in the recovery process, protect your muscles from injury, and help them to grow.

Best Quality Protein Sources


Where should you get your protein?  Your first thought might be to go and get a slab of steak.  Yes, it would give you a ton of protein, that’s for sure, but it would also load up your body on saturated fat, and you don’t want that.  The trick with choosing protein sources is to pick foods which will give you those complete proteins we discussed earlier without the adverse cardiovascular consequences that come from eating too much red meat.

So what are the healthiest protein food sources?

  • Seafood.  Seafood is a great choice because it is generally low in fat.  Along with protein, seafood also offers you other types of nutrition you need and which many of us are short on, in particular omega-3 fatty acids.  This is the good type of fat, the kind that actually boosts your cardiovascular health!  Omega-3 fatty acids boost brain power, stabilize moods, and reduce inflammation throughout your body as well.
  • Poultry.  Poultry is a great lean source of protein, especially if you stick with the white meat and steer clear of the dark meat.  Dark meat has more fat in it than white meat.  Also, be aware that the skin has tons of saturated fat in it, so remove it before you cook the meat.
  • Eggs.  For many years, eggs got a bad rap, and a lot of us have learned to avoid them as a result.  But eggs are actually loaded with nutrition, especially protein!  In moderation, they are very good for you.  An egg a day is an easy, healthy, and delicious way to get the protein you need.
  • Dairy foods.  Eating foods like cheese, milk, and yogurt is not only a great way to get the protein you need each day, but also calcium to nourish your bones.  If you like cottage cheese, that is one of the best sources you are going to find!  A cup of cottage cheese has around 25 grams of protein!
  • Almonds.  An ounce of almonds contains six grams of protein, along with other awesome nutrients like vitamin E, magnesium, manganese, and dietary fiber.
  • Beans.  Did you know you can get the same amount of protein in half a cup of beans as you can from an ounce of steak?  This is a great vegan source!
  • Lentils.  While we’re at it, we can’t forget to mention legumes!  They are another excellent vegan option, containing tons of protein along with potassium, magnesium, folate, iron, fiber, copper, and manganese.
  • Lean beef.  You don’t have to give up red meat altogether.  In fact, if you shop specifically for lean beef, you can steer clear of saturated fat while still enjoying all the other nutritional benefits of red meat.  Beef includes protein, iron, zinc, vitamin B12, and lots of other great stuff you need to function at your best.
  • Oats.  Just half a cup of raw oats contains a whopping 13 grams of protein.  Oats also contain a healthy dose of vitamin B1, magnesium, manganese, and fiber.  That is why oatmeal is one of the most nutritious breakfasts around.
  • Protein supplements.  Earlier I introduced you to a variety of different types of protein supplements.  Whey powder and other types of protein supplements still make some of the best choices for boosting your protein intake.  In particular, if you are pressed for time and do not want to cook a protein-rich meal, or if you are an athlete who really does need a much higher amount of protein than the RDA, you cannot go wrong with supplements.  Just blend a healthy shake, head to the gym, and enjoy the results!

If you decide to use protein supplements, make sure to read the label carefully!  Not all supplements have the same level of quality.  Some may use inferior protein sources or contain unwanted additives.  Still others may be healthy, but contain dairy products you do not want in your diet if you are a vegan.  If you have gluten sensitivity, watch out for protein powders containing gluten.  Also steer clear of soy products if you have difficulty digesting soy or have a hormonal imbalance like estrogen dominance which soy could have an adverse impact on.

Protein Do’s and Don’ts


Learning about a topic like protein in-depth can be eye-opening, but it can also be overwhelming, because there is just so much to remember.  The fact that there is still a great deal of contention even among researchers can cause confusion.  Then there is the fact that the recommendations you follow may not be the same recommendations that someone else should follow.  The RDA can guide your protein intake, but your own individual needs may require that you make adjustments.

So let’s go over a list of quick reminders.  If you forget some of what you learned in this article, this list should be your go-to source.

When eating and supplementing protein, DO:

  • Assess your individual needs based on your sex, age, weight, and activity level.  Use the RDA as a starting point, but do not assume that it is an exact assessment of your individual requirements.
  • Ask yourself what you are trying to accomplish.  Before you know how much protein you need in your diet, you need to first figure out why you need it.  Are you trying to cover gaps in your existing diet so that you meet the RDA?  Are you trying to boost protein in conjunction with a more intense resistance training program so you can bulk out?  Are you just trying to stay full so you can lose weight?
  • Increase protein intake proportionally to the increase in your activity levels.
  • Eat more healthy sources of protein which provide you with other nutritional value.
  • Use whey protein powders and other protein supplements as needed to meet your requirements.
  • Continuously measure your progress toward your goals.  Consider how you look and feel physically.  Check to see if you are losing, maintaining, or gaining weight over time.  Is it in the form of muscle mass or fat or both?  Make adjustments as you go.

When eating and supplementing protein, DO NOT:

  • Assume that what is right for someone else is automatically what is right for you.  For someone who isn’t working out much, the RDA may be perfect.  For your friend at the gym who does heavy resistance training, twice the RDA may make sense.  If you only do light to moderate exercise, the perfect amount for you probably is somewhere in between.
  • Increase your protein levels if you are not increasing your exercise and you are already getting enough protein.  You will not automatically start bulking out more if you are working out the same amount and eating more protein.  If you do put on more muscle, you can expect to put on more fat too.  There is also the chance you will just end up burning both.
  • Avoid adding more protein to your diet when it makes sense just because you have heard that high protein is always a bad idea.  If you are planning on working out a lot more than you used to and focusing on strength training, you probably do need more protein.
  • Try to increase your protein intake exclusively through incomplete protein sources.
  • Attempt to increase your protein intake by eating a ton of red meat which is high in saturated fat.
  • Assume what you are doing now is what you should keep doing later.  As you move closer to your workout goals and your overall body weight and composition starts to change, your protein intake needs will change too.
  • Believe everything you read or hear about protein.  There are so many misconceptions floating around, and remember, even scientists still do not fully agree on everything about protein.  Sometimes people mislead you on purpose, other times they mislead you because they themselves have been misled.  Your best bet is to do the research yourself.  If it makes sense for you to do so, try increasing your protein intake if you think you need to.  Let science be your guide, and draw your own conclusions based on what has the best positive impact on your health.


Nutritionists and athletes have known the vital importance of protein for a very long time, but our understanding of it is still imperfect.  What we do know is that protein is essential to numerous functions in your body, and is a key component in the composition of all your tissues.  Meeting your RDA is vital if you want to keep your body functioning at its best.

Should you exceed your RDA?  If you are sedentary or work out lightly, then you are probably just fine if you are getting what the Food and Nutrition Board recommends.  If you work out moderately, a moderate increase in protein through supplementation and diet changes may be just what you need.  If you are working out intensely, you may need a lot more protein.  You do not want to be excessive in your protein intake (too much of anything can harm you), but generally speaking, protein is healthy, not harmful.  So long as you are staying within reasonable bounds and what you are eating makes sense given your activity levels, then you should be in great shape!


  • How much protein do I need?

The amount of protein you need depends on various factors, such as age, weight, and activity level. However, as a general rule, adults need at least 0.8 grams of protein per kilogram of body weight per day.

  • What are the best sources of protein?

Some of the best protein sources include meat, fish, eggs, dairy products, beans, lentils, nuts, and seeds.

  • Can you get too much protein?

Yes, consuming too much protein can harm your health, particularly if you have kidney disease. Excessive protein intake can also lead to weight gain, as the excess protein is converted to fat in the body.

  • Do vegetarians and vegans get enough protein?

Yes, vegetarians and vegans can get enough protein from plant-based sources, such as beans, lentils, tofu, nuts, and seeds. However, they may need to consume a slightly higher amount of protein to compensate for the lower quality of plant-based protein.

  • What happens if I don’t get enough protein?

If you don’t get enough protein, your body may not be able to repair or replace tissues as quickly, which can lead to slower healing times and a weakened immune system. You may also experience fatigue, weakness, and muscle loss.

Andrew Brewer

Andrew Brewer

Andrew Brewer started Fastingapps.com to give people the guidance that he never received when he was first starting. His goal is to make your goals achievable and to offer you only the best fasting apps that the internet has to offer. You're not on your own - Andrew and the entire family of reviewers at Fastingapps.com are here with you every step of the way!