What it does in the body
- Primary activator of mTORC1 muscle protein synthesis pathway
- Skeletal muscle energy substrate during exercise
- Insulin secretion stimulation
- Wound healing and tissue repair signaling
- Regulation of muscle satellite cell proliferation
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | 39mg/kg/day (~2.7g for 70kg minimum; 7-12g optimal for athletes) | WHO/FAO/UNU |
| Adult female | 39mg/kg/day (~2.3g for 60kg) | WHO/FAO/UNU |
| Pregnancy | 50mg/kg/day | WHO |
| Children | 44-73mg/kg/day depending on age | WHO |
| Older adults | 39mg/kg/day minimum; 2.5-3g per meal recommended for anabolic threshold | ESPEN/PROT-AGE |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Whey protein isolate | 14g per 100g | global |
| Parmesan cheese | 3.5g per 100g | europe |
| Chicken breast (cooked) | 2.4g per 100g | global |
| Beef (lean, cooked) | 2.2g per 100g | global |
| Tuna (cooked) | 2.1g per 100g | global |
| Soybeans (cooked) | 1.2g per 100g | east-asia |
| Pumpkin seeds | 1.4g per 100g | mesoamerica |
| Spirulina (dried) | 4.9g per 100g | global |
If you don't get enough
Mild: Reduced muscle protein synthesis response to meals, slower recovery
Moderate: Accelerated muscle loss, impaired wound healing, fatigue, metabolic dysfunction
Severe: Profound sarcopenia, failure to thrive in children, severely impaired immune function
Time to onset: Blunted anabolic response within days of subthreshold intake; clinical sarcopenia over months
Too much
Upper limit: No established UL; doses up to 12g/day used in clinical studies. Very high chronic intake may deplete valine and isoleucine
Nausea, ammonia buildup (in liver disease), potential valine/isoleucine depletion causing pellagra-like symptoms
How well you absorb it
92-97% from animal sources; 80-90% from plant sources
Helped by: Whey protein (fastest leucine delivery), Insulin co-secretion from carbohydrate co-ingestion, Vitamin B6
Hindered by: Excess isoleucine and valine (competitive absorption), Impaired gut absorption in celiac/IBD
Cooking & storage
Heat-stable; normal cooking and baking preserve leucine. Maillard reaction at very high temperatures can reduce available leucine. Milk pasteurization has negligible effect on leucine content.
Nutrisize Health totals every nutrient from what you actually eat, against targets set for your age and sex, and flags what's short — across 4,995 foods, on your device.
