加载中…
Place · Level 3 · Condition
HPO 轴 4 期 · FIGO 正常上限 · 前列腺素 → NSAID 时机窗 · PMDD vs PMS · 经前/中/后三段实操 · 经期禁忌拆穿
cofactor · 1
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.
depletes · 1
↮Iron
Blood carries about 0.5 mg of iron per mL, and a period typically loses 30-40 mL — so 15-20 mg of iron leaves with it. That once-a-month exit is the main reason a menstruating woman's iron requirement is nearly double a man's (the recommendation is set near the heavy end of the range, not the average). Above 80 mL is heavy menstrual bleeding, and the iron ledger more than doubles.
Why the ledger does not balance itself
The debit side is simple: 15-20 mg of iron leaves with each period. The credit side is the hard one — iron is not 'you get what you eat'; it is throttled by **absorption**. Plant-source non-heme iron absorbs at only 2-20%, and swings hard with the meal (tannins in tea and coffee cut roughly 60%; calcium and phytate each take a share). Animal-source heme iron holds steady at 15-35%. That is why the RDA is **18 mg/day** for women against 8 mg for men — the near-doubling exists to cover that monthly exit. And note: that figure is set **near the heavy end of the range, not at the average**.
The warehouse empties before the blood does
The body does not wait for haemoglobin to fall before it feels this. The monthly exit draws first on the **ferritin warehouse** — about 60% in the liver, 25% in bone marrow. Clinically, serum ferritin is the most sensitive read on stored iron: **below 15 µg/L is absolute deficiency (an empty warehouse)**, 15-30 is borderline. Which means someone with a perfectly normal blood count can already be scraping the bottom — fatigue, hair shedding and dropping endurance often arrive before anaemia does. So checking iron cannot mean checking haemoglobin alone.
camaschella-2015When this stops being a nutrition problem
Losing more than **80 mL** meets the definition of heavy menstrual bleeding, and the iron ledger more than doubles — at that scale, diet cannot catch up. The practical trouble is that nobody can measure 80 mL at home. Usable proxies: needing to change a pad or tampon every one to two hours, having to get up at night to change, passing large clots, or bleeding longer than seven days. When those show up, the question to ask is **why is the bleeding this heavy**, not **how much iron should I take** — the latter is topping up a tap nobody turned off. This is education, not care; see a clinician for diagnosis.
regulates · 5
Endometriosis is oestrogen-driven: ectopic endometrial tissue proliferates, bleeds and inflames along with the cycle's hormonal swing, which is why the pain is cyclical rather than constant. The endometriosis story closes by pointing back at menstrual-cycle itself.
In the luteal phase the core-temperature threshold band narrows, so the same warmth feels hotter. That thermostat shares part of its KNDy neuron pathway with perimenopausal hot flushes — one set of switches under two experiences.
The HPO axis hangs off the body clock, so time-zone shifts and rotating shifts disturb the cycle — the same family of causes as stress, energy shortfall and rapid weight change: all of them telling the hypothalamus that now is a bad time.
Primary dysmenorrhoea is prostaglandin-driven, and 1-2 g/day of EPA/DHA shifts the balance away from the inflammatory prostaglandins — upstream of the same COX pathway NSAIDs act on, only slower and gentler.
B6 has limited but real evidence for premenstrual symptoms. It is also one of the few water-soluble vitamins that harms when overdone — chronic intake above 100 mg/day risks peripheral neuropathy. Remember both ends of this line.