Understanding Protein: Which protein is best? What is the difference between a meal replacement and a protein supplement?

by Dr Suk Cho July 24, 2018

Understanding Protein: Which protein is best? What is the difference between a meal replacement and a protein supplement?

Protein is present in every cell, and thus every part, of your body. Protein plays an important role in building, repairing and maintaining your cells and your body. It is also the most satiating macronutrient, which makes it an especially important part of a diet when you’re trying to lose weight.

According to NPD market group research, about 78% of consumers want more protein in their diet to lose weight, get stronger and support age-related muscle loss. Thus, consumers are willing to look beyond meat in order to meet their protein needs. Linking protein-rich diets to weight loss has caught marketer’s and consumer’s attention. Hence the rise of high protein and low carb diets like Paleo, Atkins, South Beach, the Zone, etc. It is evident that protein is more popular than ever, and protein-related topics pop up in social media, web-based ads and many commercials lately.  

What is protein?

Proteins are large molecules composed of a polymeric chain of 20 or fewer different amino acids. Amino acids consist of carbon, oxygen and hydrogen as well as some sulfur and phosphorous. They are different from fats and carbohydrates in terms of nutritive benefit, metabolism and biochemical importance. Most of us know that proteins help build and maintain muscles but they also have many other functions. Proteins may serve to build structural materials like collagen or keratin in skin and hair, as enzymes to metabolize or breakdown molecules, as transporters to carry minerals, and as regulators for the immune system and gene expression.


What properties are best for proteins?

Proteins from different sources (i.e., milk, pea, soy, etc.) differ in their amino acid content, their bioavailability, and their rate of absorption.  These factors vary the ability of proteins to help with satiety, provide blood amino acids to repair and grow muscle as well as rate of protein absorption for people who need a slower absorption to feel fuller or quick uptake of proteins needed in geriatric populations.  That is, proteins from different sources have different characteristics and behave differently in our bodies.  Formulators develop a wide range of products using proteins, from infant formula, to diabetic products, and muscle building protein shakes.  To create the most effective formulas, it is critical to have knowledge of types of proteins, how much proteins per serving is required, how many servings per day, the protein absorption and amino acid profile.


What is the best protein source for lean muscle build up for sport and weight loss?

The proteins with branched-chain amino acids (BCAAs) are best used for building and repairing muscles.  BCAAs provide an important source of energy, and they promote protein synthesis in muscles and prevent muscle breakdown.  In a controlled study, the group that took BCAA supplements gained more lean mass and lost more weight compare to men who did not take BCAAs with resistance training.  BCAAs are three essential amino acids that you must obtain through your diet (your body does not produce them).  They are leucine, isoleucine and valine, and you can count on getting varying amounts of all three amino acids from protein-containing foods.  The best sources of BCAAs are meat, chicken, fish, dairy products and eggs. Whey protein concentrates is another great source for boosting your intake of BCAAs.  

Although many plant based proteins may lack one or two essential amino acid (EAA), you may still be able to obtain BCAAs from plant based food like soy beans, brown rice, and nuts.  Though at higher dose might be necessary to get an equal amount of BCAAs. 

Recently, the market for amino acid supplementation has increased significantly.  While bodybuilders and hard-core athletes have popularized the use of BCAAs for muscle growth and maintenance, there is evidence that all EAAs including BCAAs should be taken in the form of protein instead of simple amino acids as certain small polypeptides have other significant roles in our body like cellular communicators (cytokines, etc).  And unbranched chain essential amino acid can play other roles like stimulating the production of cellular energy and promoting cellular repair.  I personally believe having whole protein with all EAAs and higher BCAAs would be more beneficial and nutritive than simple amino acid supplementation.

There are fast-digesting proteins and slow-digesting proteins. Which is desirable? It depends on the goal.

Proteins have many property differences like digestion ease and absorption.  Whey protein digests quickly, making amino acids and their muscle-repairing benefits quickly available to the body which is great for post-workout recovery.  Soy protein and Casein, by contrast, is slower to digest and absorb.  Some studies also suggest that consuming whey protein during and/or after exercise may improve strength and support muscle function and fatigue. 

Protein digestibility is most commonly measured by a ratings system called the Protein Digestibility Corrected Amino Acid Score and some examples are represented below.


Protein Source

Protein Absorption Time

Whey protein isolate

60-90 minutes

Whey protein concentrate

2-3 hours


3-4 hours

Soy Protein

3-4 hours


3-4 hours



Bioavailability is the percentage of the absorbed protein that can be used by your cells thus your body. The higher the number the better the protein is used by your body.

Protein Source

Bioavailability Index

Whey Protein Concentrate


Whole Egg


Cow’s Milk


Egg White






















Protein Meal Replacement vs Protein supplements?

Many people have asked me about the differences between meal replacements and protein supplements. There are no scientific definitions to distinguish them and there are some similar general characteristics of these products.  Simply put, meal replacements are intended to replace a meal therefore they are designed to be more filling and contain more calories and offer a balance of other nutrients compared to a typical protein supplement.   In addition, though meal replacement claims are regulated in countries like Australia and Canada, they are somewhat antiquated.  And as far as I know, there are no regulations in the US for meal replacements. 

Meal replacements and protein supplements can both support your body composition and athletic performance goals. They do have differences in their targeted intentions, nutritional profiles and benefits.  While exact nutritional specifications differ between brands, many products share the same general characteristics.   There are a number of differences in calories and protein content as well as other macronutrient and micronutrient content between these two categories of products.

In my experience over several decades of research and product development, the best meal replacement is a well-balanced shake with high protein (Whey-based) and high dietary fiber to provide satiety and keep you fuller longer without being so high that it causes gastric issues. Also, it contains complement of other nutrients like healthy fats and reasonable percentage of the Recommended Daily Intake (RDI) of vitamins and minerals (some brands exceed 500% of RDI for vitamins!)


Although meal replacements are higher in calorie than protein shakes, they tend to be lower in calories than actual meals, which can aid in dieting and weight loss programs.  Meal replacement shakes typically contain between 250 and 400 calories.  Most protein supplements appear to be designed to be supplement for body building or sports that require additional protein supplementation.  They tend to be whey protein isolates with 100-150 calories per serving.

Protein Content

Protein shakes typically provide about 25 g of protein per serving, while the range of protein in meal replacements differs widely.  Meal replacements intended for general health (or what is  typically prescribed to cancer patients) may be lower in protein with around 10 g per shake.  Those intended for muscle building and dieting may contain up to 35 g.  

Carbohydrate Content

Protein supplements typically have very few carbohydrate, typically less than 5 g of carbohydrates, as they are not intended to be a meal replacement. Meal replacement products tend to contain carbohydrates to make the nutritional profile like a real meal. Both carbs and added sugars can vary significantly from brand to brand. Meal replacements that are beneficial for dieting will contain dietary fiber, a nutrient that helps in digestion and makes you feel fuller thereby helping you consume fewer calories throughout the day.

Fat Content

Protein supplements are typically low in fat, with 3g or fewer, while the fat content in meal replacements varies. Meal replacements that are lower in carbohydrates tend to be higher in fat, and may be useful for low-carbohydrate diets or more balanced in terms of fat and carbohydrate content.

Vitamins and Minerals

Protein supplements tend not to contain any added vitamins and minerals other than those provided by the protein source. Although not all meal replacements contain added vitamins and minerals, many do.



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  3. European Journal of Applied Physiology and Occupational Physiology

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  1. The Journal of Strength & Conditioning Research: April 2010 - Volume 24 - Issue 4 - p 1125-1130
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Dr Suk Cho
Dr Suk Cho

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