How Much Protein Can the Body Absorb?

Is there a limit to how much protein your body can absorb at one sitting? Nutrition Diva weighs in on this widespread rumor.

Monica Reinagel, MS, LD/N, CNS
4-minute read
Episode #256

Protein: The Body's Tinker Toy Set

Remember Tinker Toys? It's a collection of sticks and wheels that you can put together to build anything you want. You could build a Tinker Toy house, for example. Then, you could take apart the house and reconfigure the same pieces into an airplane. 

Protein is sort of like the body's Tinker Toy set.  Every protein is made up of special molecules called amino acids, which are like the individual Tinker Toy pieces. When you digest protein, your body breaks it down into the individual amino acids and then uses them to build enzymes, hormones, immune factors, transport and storage molecules, and all kinds of other useful things, including bigger biceps.

Protein is an essential nutrient because you can't get amino acids from fats or carbohydrates. No amino acids, no enzymes. No enzymes, no life. 

When the stakes are that high, it's not surprising that the body prioritizes its use of amino acids. Survival first; six-pack abs second.  But when the body has all the amino acids it needs, protein can also be used as an alternative source of energy or calories.  In other words, if you have some Tinker Toy pieces left over after building your house, you can burn the extras for heat! 

And this is the sense in which all of the protein you take in does get utilized. Protein beyond what your body needs to replenish its amino acid pool (or can put to use for muscle building) is metabolized into glucose and used for energy. And whenever you have more food energy than you need, the surplus is stored as fat. Nothing is wasted.

Advantages of Protein as an Energy Source

As long as you're not taking in more calories than you're burning each day, there's no harm in using protein as a source of energy.

So, is your post-workout shake with 50 grams of protein a waste? In terms of repairing and building up your muscles, a shake with 30 grams of protein might be just as effective. But as long as you're not taking in more calories than you're burning each day, there's no harm in using protein as a source of energy. In fact, there may be some advantages - all of which I've discussed in previous episodes. 

1. Protein takes longer to digest than carbohydrates, which means that calories from protein tend to keep you full longer than calories from carbohydrates. This can be very helpful in controlling calorie intake and managing your weight.

See also: 3 Tips on How to Eat Less Without Feeling Hungry

2. Protein doesn't cause sharp spikes in blood sugar, which reduces your risk of diabetes. 

See also: What Is High Glucose?

3. Protein can modestly boost your metabolism, or the rate at which your body burns calories.

How Much Protein Should You Eat?

There's a big range in the amount of protein that's considered to be acceptable - and it depends on what your goals are.

It doesn't take a whole lot of protein to keep the body's amino acid Tinker Toy set stocked - about 10% of calories or around 50 grams a day will do it for an average-sized person. Even vegetarians should have no trouble getting that amount.

The muscle building benefits of protein seem to max out around 20% of calories. And if you want to take advantage of protein's appetite-taming and metabolism-boosting abilities, it's OK to go as high as 30%-35% of calories from protein - as long as you don't have any medical issues (such as reduced kidney function).

One last tip: Your body does use extra water to digest protein. So, if you're increasing your protein intake, be sure to increase your fluid intake as well to avoid dehydration

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Protein sources images courtesy of Shutterstock.


About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.