加载中…
Place · Level 3
20 个氨基酸 · 9 个必须吃来 · 一天的身体都在拆建 · 不同人群需求差很多
synergy · 3
mTORC1 activation requires both leucine threshold (~2.5 g) and mechanical signaling. Training + protein are the minimum sufficient conditions for hypertrophy; either alone collapses the other's value.
Post-exercise GLUT4 + Leu-mTORC1 share the insulin/AMPK window: glycogen reload + MPS run together (30-90 min). Protein + adequate carb beats protein alone for recovery.
→Zinc
Animal protein prises zinc out of phytate's grip in the gut lumen, so the plant-source zinc in the same meal absorbs better too — that's the other half of why vegans need more zinc.
cofactor · 13
Age-related 'anabolic resistance': per-meal leucine threshold rises from ~2 g (young) to ~3 g (old) — requires 30-40 g high-quality protein per meal + resistance training to drive mTORC1 and preserve muscle. 1.2-1.6 g protein / kg / d consensus (PROT-AGE 2013).
RDA 0.8 g/kg/day prevents deficiency; training adaptation needs more. Morton 2018 meta sets the breakpoint at 1.62 g/kg/day; trainees should target 1.6-2.2 g/kg/day.
Leucine is sensed inside the muscle cell and flips mTORC1, the master switch for protein synthesis. A meal of 25-40 g of quality protein captures most of the available response; larger doses still add something, and last longer (100 g drives a bigger, >12-hour response than 25 g — Trommelen 2023), just with diminishing returns. What actually builds muscle is the daily total (rising benefit up to roughly 1.6 g/kg — Morton 2018), not policing a per-meal ceiling.
What the body lacks is never the amino group but the carbon skeletons of the 9 essential amino acids: transaminases move an amino group from one molecule to another all day, and the coenzyme doing it is PLP, the active form of B6.
Antibodies, complement and immune cells are all built from protein, and older adults need more of it than the young (PROT-AGE puts healthy elderly at about 1.0-1.2 g/kg/day) — plus the exercise to use it. Falling short costs twice: muscle lost and immune raw material short.
Protein needs after menopause are badly underestimated: the 0.8 g/kg/day RDA is not enough and the real target is 1.2-1.6. With oestrogen gone the anabolic signal is weaker, so the same protein drives less synthesis and the shortfall has to be made up in quantity.
Bone is not only mineral: its matrix is collagen, and collagen needs protein. In fracture recovery or chronic illness the target is 1.2-1.5 g/kg/day, delivered as 25-40 g per meal with at least 2.5 g of leucine to drive synthesis — the distribution is easier to overlook than the total.
Biotin is cofactor for MCC and related carboxylases that catalyze branched-chain amino acid (Leu/Ile/Val) catabolism — a hidden BCAA pathway beyond the carbohydrate-metabolism story.
→HMB
HMB is a metabolite of roughly 5% of leucine and works on the anti-catabolic side; the mTOR synthesis trigger is leucine itself. Different switches — which is why adding HMB on top of adequate protein buys little.
Collagen synthesis needs an adequate amino-acid supply (glycine and proline especially), and that comes first from total daily protein, not from a special powder.
Resistance training plus enough protein is the pair that actually preserves muscle here: the 15-30% acute testosterone bump after a session is not the point — leucine driving muscle protein synthesis through mTOR is. No special testosterone-boosting programme required.
The body is doing different work at different points in the cycle: in the follicular phase, with oestrogen rising, strength and recovery usually beat the luteal phase — a window for intensity. Meanwhile the endometrium rebuilds monthly, and the raw material for that repair is 1.2-1.6 g/kg of protein a day.
Inadequate protein is the item most often skipped on a fatigue work-up; the people at risk are older adults and long-term dieters. Short of protein, muscle gets used as raw material and both strength and stamina fall together.
depletes · 1
Chronic alcohol → protein-energy malnutrition + B1/B12/folate malabsorption + accelerated sarcopenia. Alcoholic myopathy isn't only heavy-drinker territory — moderate intake + elderly = high risk.
contrast · 1
Protein harming kidneys is a common misreading: on the real CKD risk list it ranks low, behind diabetes, hypertension, nephrotoxic drugs and aristolochic acid. For healthy people 1.6-2.0 g/kg/day is safe.