
If you're lifting and eating plenty of protein but still not seeing the muscle you expected, zoom in one level: **amino acids**. They're the building blocks of protein, and a few specific ones are disproportionately important for **muscle protein synthesis (MPS)**. The good news: once you know which ones matter, it's easy to adjust your meals so your training actually shows.

## The headliners

**Leucine (the "on" switch).**

Leucine is the key amino acid that flips on mTOR, the pathway that kick-starts MPS. Think of it as the ignition for your post-workout meal. You'll find it in whey, dairy, eggs, beef, chicken, and soy (tempeh/edamame).

**Essential amino acids (EAAs).**

Your body can't make EAAs, so you have to eat them. Leucine gets a lot of hype, but the **full set of EAAs** is what actually **builds** new muscle proteins. In practice, that means whole protein sources (whey, dairy, eggs, meat, fish, soy, mixed plant proteins) beat BCAA-only powders.

**Lysine (easy to miss if you're grain-heavy).**

Lysine is often the **limiting amino acid** in cereal grains – one reason lifters who eat mostly grain-based proteins may want to lean harder on legumes/soy. If your meals are bean/soy-forward, you're usually covered.

## BCAA vs EAA vs whole protein (what actually works)

Short version: **BCAAs alone aren't enough** to maximize MPS; studies show they don't outperform complete protein or EAA blends. Your best bet is simply **protein-rich foods** (or whey/soy) that deliver all the EAAs, with enough **leucine** to flip the switch.

## How much protein and how to spread it

Across meta-analyses, total daily protein around **~1.6 g/kg body weight** tends to maximize strength and size with resistance training (going much higher shows little extra benefit for most people). Spreading protein more evenly across meals appears to boost 24-hour MPS—practically, that looks like **~25–40 g protein per meal**, which usually brings **~2–3 g leucine** from high-quality sources. Older lifters may benefit from the **upper end** of that range due to "anabolic resistance."

## If you're plant-forward

You can absolutely build muscle on plants. Two tips keep it simple:

- **Prioritize leucine-rich plant proteins:** soy foods (tofu, tempeh, edamame), pea protein, *plus* legumes.
- **Mix your sources:** grains are often low in **lysine**, while legumes are lower in **methionine,** together they cover each other's gaps.

## Quick meal ideas that check the boxes

- Greek yogurt + whey + fruit (dairy + whey = leucine rich)
- Tofu stir-fry with edamame and rice (soy + grain = EAA complete, good lysine)
- Omelet with cheese + potatoes (egg/dairy combo = high leucine)
- Lentil pasta with tempeh crumble (legume + soy for coverage)

## The bottom line

To build muscle, aim for **enough total protein**, **evenly split across meals**, and make sure each meal delivers a solid **leucine punch** within a **complete EAA package**. Whole foods make this easier than you think; supplements are just a convenience tool.

If you'd rather not guess, **tracking your amino acids** helps you see whether each day's meals hit your targets, especially **leucine** and total **EAAs**. In **Microgram**, you can track amino acids alongside protein and other macros/micros, spot low-leucine meals, and fix gaps fast so you're getting **the right amount** for your goals.

## References

- Drummond MJ, Rasmussen BB. Leucine-enriched nutrients activate mTOR to stimulate muscle protein synthesis. *Curr Opin Clin Nutr Metab Care.* 2008. [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC5096790/)
- Wolfe RR. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? *J Int Soc Sports Nutr.* 2017. (BCAA alone ≠ superior to whole protein/EAA.) [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC5568273/)
- Church DD, et al. Essential amino acids are required to increase muscle and whole-body protein synthesis. *Nutrients.* 2020. [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC7760188/)
- FAO/WHO. *Dietary protein quality evaluation in human nutrition (DIAAS report).* 2013. [FAO](https://www.fao.org/ag/humannutrition/35978-02317b979a686a57aa4593304ffc17f06.pdf)
- Poutanen KS, et al. Grains as protein: lysine often limiting in cereals. *Nutr Rev.* 2022. [PubMed](https://pubmed.ncbi.nlm.nih.gov/34741520/)
- Morton RW, et al. Protein intake ~1.6 g/kg/day maximizes hypertrophy with resistance training. *Br J Sports Med.* 2018. [PubMed](https://pubmed.ncbi.nlm.nih.gov/28698222/)
- Layman DK, et al. Protein distribution (≈30 g/meal; ~2.5 g leucine) improves 24-h MPS vs skewed intake. *Nutrients.* 2024. [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC11099237/)
- Paulussen KJM, et al. Older adults show higher leucine needs (anabolic resistance). *Nutrients.* 2021. [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC8131552/)
- Ferrando AA, et al. Higher-leucine EAA mix increases MPS vs lower-leucine profile. *Clin Nutr.* 2023. [PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10561576/)
- Casperson SL, et al. Leucine supplementation and muscle protein synthesis (mTOR). *Metabolism.* 2012. [ScienceDirect](https://www.sciencedirect.com/science/article/abs/pii/S0261561412000210)

*Educational only; not medical advice. Always confirm supplement use with your clinician.*


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