Vitamin A and vitamin C have opposite temperaments.C is water-soluble — surplus is flushed out in urine, so overdose is rare. A is fat-soluble — surplus is stored.
Stored where? In the liver. About nine-tenths of the body's vitamin A sits in the liver's stellate cells.
So the slice of pork liver in your hand is that pig's lifetime vitamin A warehouse. Eating liver is not topping up a little; it is moving somebody else's entire stock into yours — and that one line is where everything below starts.
2 · One serving is nearly twice the ceiling
One 100 g serving of cooked pork liver exceeds the adult daily vitamin A ceiling; the warehouse absorbs it occasionally, but meal after meal its headroom runs out.The adult tolerable upper intake level () is 3000 µg per day. And 100 g of cooked pork liver carries about 5400 µg RAE.
One serving is 1.8× the ceiling. The US Recommended Dietary Allowance () is 700 µg RAE for adult women and 900 µg for men — so one serving is six to eight days' worth of the RDA.
That does not mean one meal harms you. The warehouse has headroom and can absorb an occasional delivery. What matters is the next line: what absorbs it is headroom, not throughput. Meal after meal, the headroom runs out, and the surplus has nowhere to go — which is where the trouble starts.
3 · Once full, it starts to spill
Once the warehouse is full, free retinol spills into the blood and acts on cell membranes, so the signs of excess cluster in four places: brain, skin, bone and liver.Brain — membrane permeability is disturbed, the making and clearing of cerebrospinal fluid falls out of balance, intracranial pressure rises: headache, nausea and vomiting, blurred vision, double vision when severeSkin — the junctions between epidermal cells are weakened and the horny layer lifts off in sheets: cracking, flaking, large-area peeling when severeBone — bone is torn down and rebuilt throughout life; excess speeds tearing down and slows building up, so the balance tips: bone pain, and brittleness over timeThe liver itself — stellate cells held distended for long enough switch from storing fat to making scar, laying fibre around themselves. Not one burn, a slow hardening Acute and chronic are two timescales of one mechanism. Acute comes fast and clears fast (stop, and the liver takes the circulating batch back). Chronic has no dramatic start, so the signs get blamed on something else — bone pain on overuse, dry skin on the season — and recovery takes months, because the liver's stock has to be spent down.
4 · Hold the warehouse, and you can do the arithmetic
For a fat-soluble nutrient what matters is the average over time, not any one day — for anything that accumulates, a heavy day and a light day cancel out.So the portion is calculated, not guessed: 1-2 times a week, 50-100 g each time. A week's 100-200 g of cooked pork liver is 5400-10800 µg ; spread over seven days that is 770-1540 µg RAE a day — comfortably under the while still one to two times the US , enough to fill a gap.
Children are worked back from their own ceilings (600 µg RAE at 1-3, 900 at 4-8, 1700 at 9-13), which lands on once a week, 30-50 g. The point is that children have much lower ceilings of their own; it is not about liver size (for their body weight, children actually have proportionally larger livers than adults).
Hold those three ideas and these stop needing to be looked up:
Cod liver oil counts against the quota; carrots do not — cod liver oil is preformed vitamin A and goes straight into the warehouse, while carrots are raw material converted on demand. So "I had carrots today, I'll eat less liver" is bad accounting, and "I had liver today, I'll take the cod liver oil anyway" is the dangerous oneThe same serving is a supply to someone depleted and a load to someone replete — what a dose means depends on your stock. Which is why "it is nutritious" never implies "you should eat more of it" 🔴 Pregnancy is a different matter, and a stricter one. In a prospective cohort, preformed vitamin A from supplements above roughly 10,000 a day was associated with cranial-neural-crest birth defects ( 4.8, 95% 2.2-10.5); the band above 15,000 IU a day from food plus supplements carried a prevalence ratio of 3.5; beta-carotene from fruit and vegetables is not teratogenic. 100 g of cooked pork liver converts to 18,000 IU — halved to 50 g it is still 9,000 IU, right against the line. So "halve the portion" is not enough in pregnancy, and the UK NHS simply puts liver and liver products (pâté included) on the do-not-eat list. Guidelines differ between limiting and avoiding, but until your own obstetrician says otherwise, avoiding is the safer default.
General information only. Persistent bone pain, unexplained headache or widespread flaking needs a doctor, not a symptom search.