THE #1 MUSCLE BUILDING AMINO ACID

The Leucine Threshold Guide

Name: CompareWhey
Rating: 4.8

Discover why 2.5-3g of leucine per serving is the golden standard for maximizing muscle protein synthesis

2.5g

Minimum Threshold

3.0g

Optimal Amount

10-11%

Of Total Protein

What is Leucine?

Leucine is the most important amino acid for muscle building. It's one of the three branched-chain amino acids (BCAAs) and acts as the primary trigger for muscle protein synthesis (MPS) through activation of the mTOR pathway.

Triggers MPS

Activates mTOR pathway

Essential Amino

Must come from diet

Anabolic Signal

Promotes muscle growth

The Leucine Threshold Concept

Research shows that 2.5-3.0 grams of leucine per meal is needed to maximally stimulate muscle protein synthesis. This is known as the "leucine threshold" or "leucine trigger."

Below Threshold (<2.5g)Suboptimal MPS

At Threshold (2.5-3g)Optimal MPS

Above Threshold (>3g)No Additional Benefit

Key Finding: Once you hit 2.5-3g of leucine, consuming more doesn't provide additional muscle-building benefits. This is why understanding leucine content in your protein is crucial for optimizing your supplementation.

Leucine Content by Protein Type

Not all proteins are created equal when it comes to leucine content. Here's how different protein sources compare:

Whey Isolate

2.7g

per 25g protein serving

Whey Concentrate

2.5g

per 24g protein serving

Casein

per 24g protein serving

Soy Protein

1.8g

per 20g protein serving

Pea Protein

1.6g

per 20g protein serving

Whey protein naturally contains the highest leucine content (10-11% of total protein), making it the most effective protein source for muscle building.

Highest Leucine Products in Our Database

Brand	Product	Leucine	Serving Size	Type
Optimum Nutrition	Serious Mass	5.5g	336g	Mass Gainer
MuscleTech	Mass Tech Extreme	5g	285g	Mass Gainer
BSN	True Mass 1200	4.8g	310g	Mass Gainer
MuscleTech	Nitro Tech	3.3g	46g	Blend
Optimum Nutrition	Platinum Hydrowhey	3.2g	39g	Hydrolyzed

Note: Mass gainers have higher leucine due to larger serving sizes, but may not be practical for everyone.

Timing and Dosage Recommendations

Optimal Timing

Post-Workout

Within 2 hours after training for maximum MPS when muscles are most receptive

With Meals

Add to lower-protein meals to reach the leucine threshold

Daily Distribution

For optimal results, aim to hit the leucine threshold 3-4 times per day:

Breakfast: 25-30g whey protein (2.5-3g leucine)
Lunch: Whole food protein (aim for 2.5g+ leucine)
Post-Workout: 25-30g whey protein (2.5-3g leucine)
Dinner: Whole food protein (aim for 2.5g+ leucine)

Important: While leucine is crucial, total daily protein intake (0.8-1.2g per lb body weight) and overall calorie balance are equally important for muscle growth.

The Science Behind Leucine

Key Research Findings:

✓
Moore et al. (2009): Found that 20-25g of high-quality protein (containing ~2.5g leucine) maximally stimulated MPS in young men.
✓
Witard et al. (2014): Demonstrated that 20g whey protein (2.5g leucine) was sufficient to maximally stimulate MPS post-exercise.
✓
Devries & Phillips (2015): Showed that leucine content is the primary driver of the muscle protein synthetic response to protein feeding.

The mTOR Pathway

Leucine activates mTORC1 (mechanistic target of rapamycin complex 1), which is the master regulator of protein synthesis. This activation leads to increased translation of mRNA into new muscle proteins.

Practical Tips for Meeting Your Leucine Needs

Choose the Right Protein

Look for proteins with 2.5g+ leucine per serving
Whey isolate typically has the highest leucine content
Check our database for exact leucine content

Whole Food Sources

Chicken breast (3oz): ~2.2g leucine
Greek yogurt (1 cup): ~2.5g leucine
Eggs (3 large): ~1.8g leucine

Find Your Perfect High-Leucine Protein

Browse our database of 89 proteins, all with verified leucine content, to find the perfect match for your muscle-building goals.

Browse High-Leucine Proteins Calculate Your Leucine Needs →