Leucine as one key signal

Leucine is one key signal for muscle protein synthesis, but total essential amino acid intake and resistance training also matter. Leucine plays a key signaling role in activating the mTOR pathway, which contributes to initiating muscle protein synthesis — low leucine can weaken the muscle protein synthesis response, especially when total essential amino acids are also low. Animal proteins often provide higher proportions of digestible essential amino acids per serving, including leucine, than m

What this means in practice

Whey and 🥚 eggs are often among the more efficiently retained protein sources on biological value scales. Beans and lentils often score lower on biological value, meaning more total grams or complementary protein sources may be needed to match the nitrogen retention of a smaller serving of animal protein. Combining plant proteins — beans with rice, lentils with dairy — can improve the overall amino acid profile and effective biological value of a meal.

Foodbe

March 4, 2025

Protein Biological Value: Why Not All Protein Is Equal

Biological value is a measure based on the proportion of absorbed nitrogen the body retains rather than excretes — specifically, how efficiently absorbed protein is used for tissue synthesis. Egg protein has historically been used as a reference standard at 100 on the biological value scale.

Whey is often listed as equal to or slightly above egg in some biological value scales, but exact scores vary by method and source. Beans and legumes often score lower, partly because limiting amino acids and digestibility factors can reduce nitrogen retention unless total intake or complementary proteins compensate.

The calculation is nitrogen retained divided by nitrogen absorbed, multiplied by 100. This distinction matters — protein quantity alone is incomplete if the body cannot retain what it absorbs. Proteins low in one or more essential amino acids may have a lower biological value unless total intake or complementary proteins compensate.

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Foodbe.ai exists to inform consumers about the food they buy and eat. Every claim is cited. Sources: NIH, USDA, FDA, Smithsonian, and JSTOR. Found an error? Email us at admin@foodbe.ai to report any source or fact issues.