Milk, whey and soy are the protein sources FEERO prioritises in its development brief, alongside other approved options. For our bar, soy isolate is our choice over pea protein. Soy has a strong mix of amino acids and a larger set of muscle studies behind it.
That is a clear choice based on the job. A protein source should deliver useful amino acids in a recipe that tastes good and keeps calories controlled.
Why milk and whey make sense
Milk protein contains casein and whey. Both supply the essential amino acids needed to build body proteins. Whey also has a high share of leucine, an amino acid involved in the muscle building response. [1]
These are proven sources for foods with lots of protein. There is no need to reject them for sounding more processed than a handful of nuts.
A source with lots of protein is useful when space is tight. That is exactly the problem a small bar needs to solve.
Why soy is our plant preference
Soy supplies all nine essential amino acids. A 2025 review combined 17 trials of soy and milk protein. It found no clear difference in muscle mass between them. That gives soy a serious evidence base. [2]
Pea has a different amino acid pattern, with weaker levels of some sulphur containing amino acids. Soy is our preferred starting point for this job. [3]
That review does not prove soy beats pea in every direct comparison. We choose soy for its mix of amino acids and the amount of research. We are not claiming a trial proved a result it did not test.
Judge the finished serving
A source name does not tell you how much protein the bar contains. Check the grams, then the calorie cost. Use the label checklist to see where protein sources sit in the list of ingredients.
A great source in a poor ratio still leaves you with an inefficient snack. Taste and texture also need to work.
FEERO's approach is to start with strong protein options and build a useful food around them. Choosing the source is the first step. Delivering enough of it without wasted calories is the standard the finished bar must meet.