Amino acids are the building blocks of life, and dietary proteins are the body’s source of new amino acids. Therefore, the nutritional effect seen with dietary protein intake is in fact a result of the absorption of amino acids. But unlike protein sources, which must be broken down into their various individual amino acids before they can be used by the body, amino acid supplements don't have to go through the process of protein metabolism and thus come ready for complete absorption. In light of this fact, you might be left wondering which is really better—dietary protein or amino acid supplements.
There are a number of factors to consider when answering this question. So, in this article, we’re going to delve into these issues, weigh the pros and cons of each, and discuss what you need to know to choose the best approach.
Dietary Proteins—the “Natural” Way to Obtain Amino Acids
The quality of a dietary protein, as scored by the Digestible Indispensable Amino Score (DIAAS), a scoring system devised by the Food and Agriculture Organization of the United Nations (FAO), is determined by the extent to which its constituent amino acids are digested and absorbed as well as the profile of the amino acids—the amount of each amino acid relative to the others—in relation to the body’s requirements.
This includes the levels of essential amino acids as compared to the levels of nonessential amino acids. Even though the human body uses 20 different amino acids to create all the proteins it uses to function, it can, under normal circumstances, manufacture the 11 nonessential amino acids on its own. However, the nine essential amino acids must be obtained from food.
Now, there’s a school of thought in the nutrition community that says natural food sources are always better than supplements. However, the scientific basis for this perception is unclear. For example, individuals who have had large portions of their intestines removed surgically can live for many years entirely on artificial nutrition given intravenously.
The waters become particularly muddied in the case of dietary protein vs. amino acid supplements.
Amino acids in general are not only natural components of the diet (albeit packaged in the form of protein), but essential amino acids specifically are also the only macronutrients required for survival. What’s more, the nutritional purpose of dietary protein is to deliver amino acids to the body.
This being so, can we truly say that dietary protein is more “natural” than supplementary amino acids?
A further complication in distinguishing between the advantages of dietary protein and those of amino acid supplements arises when considering specific protein dietary supplements, such as whey protein powder.
Should we consider whey protein a natural protein food source?
While whey protein occurs in its unaltered form in the plastic tub of powder you buy at your local health food store, it’s still a byproduct of cheese-making—which means that milk is its original food source.
So, clearly, when it comes to distinguishing between “natural” protein food sources and amino acid supplements, there’s a lot of room for interpretation.
But rather than worry if a nutritional supplement is natural, it’s actually more important to consider whether there’s a quantifiable difference between the nutritional benefits seen with the protein that occurs as part of a normal diet and those found when using amino acid supplements.
Why Use Amino Acid or Protein Supplements?
Protein is a fundamental part of our diet—almost every biological process in the body depends on it—and optimal amino acid and protein nutrition starts with the protein component of our meals.
However, the amount of protein in an individual’s regular diet often isn’t enough to provide sufficient levels of the amino acids the body needs to thrive. There can be many reasons for this, from eating habits to lifestyle choices to health problems.
For example, college students living away from home for the first time may indulge in far more carbohydrates and junk food than high-quality protein sources. Similarly, older adults may lack sufficient protein due to loss of appetite, dental problems, or financial difficulties. And without careful food choices, people who follow a vegetarian or vegan diet are particularly at risk of protein deficiency.
In addition, there are circumstances that can increase an individual’s dietary protein needs. Participation in heavy exercise, whether aerobic or resistance training, is one example.
A 2018 study published in the European Journal of Applied Physiology (Eur J Appl Physiol) found that protein supplementation after prolonged aerobic exercise enhanced the anabolic response required for the process of muscle-building (muscle protein synthesis). And a 2008 study published in the American Journal of Clinical Nutrition (Am J Clin Nutr) demonstrated that 20 grams of high-quality protein was needed to achieve maximum muscle protein synthesis after resistance exercise.
These studies are just two among the many that have documented the positive effect of protein and amino acid supplementation on muscle mass and strength as well as physical performance.
The natural aging process illustrates another situation in which protein requirements increase. This is because the body’s muscle protein synthetic response decreases with age, leaving older adults more at risk of sarcopenia. A 2019 study published in the journal Sports Medicine (Sports Med) found that this anabolic resistance is even more pronounced in older women.
Moreover, conditions such as serious illness, injury, and surgery can all increase the body’s need for a high-protein diet.
However, any mismatch that exists between optimal protein requirements—as opposed to the recommended dietary allowance, or RDA, which is a guideline based on a variety of factors, including sex, age, and activity level—and the amount actually eaten can be addressed by taking a protein or amino acid supplement.
Protein supplements may come as relatively pure preparations (whey protein isolate is a good example). Alternatively, protein may be a component of a more complete food product that also contains carbohydrates and fat. Examples of these types of protein supplements are protein bars and meal replacement beverages.
Amino acid supplements may also come as part of a more complete nutritional supplement that includes fat and carbohydrates, but you’ll usually find amino acids supplied in a more pure form, such as a beverage, capsule, or powdered blend.
Benefits of Protein and Amino Acid Supplements
As mentioned, protein is required for almost every biological process, and the amino acids absorbed from a protein supplement thus perform a wide range of functions, including production of both brain neurotransmitters and the chemicals required for the regulation of immune function and blood flow.
However, the predominant role played by amino acids is in stimulating the production of new body proteins—via the aforementioned anabolic response that results in a net gain in protein balance—particularly those that make up skeletal muscle. The value of protein supplements has therefore traditionally been evaluated in terms of their ability to perform this action.
The extent to which a protein supplement can stimulate the production of new muscle protein, and thus increase muscle mass, is highly dependent on the specific protein and how much of it is consumed.
For example, high-quality proteins like whey protein contain close to 50% essential amino acids, while collagen protein contains only about 10%. This is important because essential amino acids are the active components of dietary proteins—the nonessential amino acids present in protein actually have no impact on the production of new muscle protein.
Consequently, the positive effects of protein intake on muscle protein synthesis are dependent on the amount of essential amino acids contained in each particular protein. Further, all nine essential amino acids are required for sustained stimulation of muscle protein production. Therefore, incomplete proteins—proteins that lack sufficient levels or include only some of the essential amino acids—are not effective on their own.
What Protein Supplement Is Most Effective?
In terms of stimulating the production of new muscle protein, whey protein has been shown to be the most effective protein supplement. In general, incomplete plant-based proteins like pea protein are ineffective. Soy protein is the exception because it’s one of the only plant-based proteins that’s classified as a high-quality protein—though whey protein is still more effective.
As alluded to earlier, the body’s response to whey protein is somewhat dose-dependent, but progressively larger doses get less and less effective. And once the level reaches 30 grams, little added benefit is seen compared with lesser amounts.
In addition, the more pure form, whey protein isolate, is more effective than the whey protein contained in a meal replacement. In fact, meal replacement protein supplements have often been shown to have little to no beneficial effect.
The problem may lie in the addition of non-protein calories in the form of carbohydrates and fat, but it’s more likely that low-quality proteins have been included with the whey protein used in the formulation. However, this is difficult to determine because product labels may be required to list total protein content per serving, but they’re not required to list how much of each protein included in the mixture is contained in each serving.
Moreover, it’s quite common to include the low-quality protein collagen because it doesn’t cost much and is easily mixed into any formulation.
So if you’re interested in using a protein supplement, and muscle protein synthesis is your goal, it’s best to look for a product that’s composed of only whey protein. But if you choose one that contains a combination of proteins, be sure they’re all high-quality proteins.
Benefits of Amino Acid Supplements
Amino acid supplements have many benefits. To begin with, the profile of amino acids in dietary supplements is completely controlled, so only active amino acids are included. Moreover, amino acid supplements are fully and rapidly absorbed.
Peak concentrations of essential amino acids also reach a high level more quickly than when a similar amount of protein is consumed. As a result, a blend of essential amino acids may stimulate muscle protein synthesis 3 times as much—or more—as a similar amount of whey protein. Which means that a very small amount of essential amino acids (fewer than 4 grams) is enough to effectively stimulate muscle building.
While amino acid supplements, particularly those made with all nine essential amino acids, have many advantages over protein supplements, there are a few disadvantages to supplements that don’t include a dietary protein component such as whey.
For example, even though peak concentrations of amino acids are reached much faster than those seen with whey protein, concentrations also fall off much faster. Thus, the response to an amino acid supplement is not as sustained as the response that might occur with whey protein.
So Which Is It—Dietary Protein or Amino Acid Supplements?
It’s clear from the above discussion that essential amino acid and protein supplements, particularly whey protein isolate, both have benefits. But one is not necessarily better than the other, especially when they can be combined for maximum benefit.
The rapid, intense response to essential amino acids can be merged with whey protein to achieve a more sustained response in a flavorful product.
Moreover, there are some circumstances, such as before physical activity, in which the rapid absorption of amino acids makes them the preferable choice—especially if your goal is to increase exercise performance and improve muscle growth, body weight, and body composition.
However, in other cases, such as after intensive physical activity, a combination of essential amino acids and whey protein is the better choice for capitalizing on the benefits of each.
In summary, both amino acids and high-quality proteins like whey protein can be useful as dietary supplements. And while a mixture of essential amino acids has many important advantages, the rather short period of stimulation is a limitation in some circumstances that can be mitigated by ingesting whey protein at the same time.