WHAT
Leucine is a branched-chain amino acid (BCAA) — just like valine and isoleucine — and is important for repairing and building muscle.

Amino acids are the building blocks of protein. Your body can make some types by itself, while it needs to obtain others from your diet. These are called essential amino acids.

WHY
Leucine intake is linked to numerous benefits:

• Getting enough leucine may prevent muscle wasting among older adults
• Also appears to help manage blood sugar levels 
• It's an mTOR activating amino acid. mTOR is a regulator of anabolic metabolism, the process of building new proteins and tissues.

HOW

• Eating foods that have complete protein gives enough of these amino acids. This includes foods such as meat, poultry, fish, eggs, and milk.
• For most adults, the current recommendation for leucine is a minimum daily intake of 121 mg per pound (55 mg per kg) of body weight, or approximately 4.4 grams per day for a 175-pound (80-kg) person
• In other recommendations, it is recommended 5 grams of leucine per meal to improve anabolic response. 
• For workout, up to 15 minutes pre-workout. If you are training in a fasting state, use 30 minutes before.
• Since leucine prolongs muscle protein synthesis after training and after meals, it can be effective for people to consume leucine 90 minutes after breakfast or lunch also, particularly where muscle gain is the goal.
• If you are concentrating on fat loss you can instead take it 30-45 minutes before a meal.