Ranked by how strong the human evidence is — best supported first.
Best supportedEnergy metabolismNot enough evidence· no source yetThen, in order
Beef or lamb liver dried at low temperature and milled into powder or capsules, concentrating it to roughly a quarter of its fresh weight. It is a food in tablet form rather than an extract.
Desiccated liver is one of the few supplements where the nutritional content is genuinely dense and genuinely documented, because it is simply liver. That is also the problem. Liver is the single richest common source of preformed vitamin A, and drying concentrates it: a daily serving of capsules can supply several times the recommended intake of retinol and approach or exceed the tolerable upper limit, which is the one nutrient where chronic excess causes real damage — liver injury, bone loss and, in pregnancy, birth defects. It is also very high in copper and in heme iron. None of this is a reason to avoid liver as a food; it is a reason to regard a daily capsule habit as a nutritional intervention with an upper bound, which is not how it is marketed.
Regulation: Sold as a dietary supplement in the US with no pre-market efficacy or safety review, and with no requirement to declare the vitamin A content that makes it worth thinking about. Sourcing claims such as "grass-fed" and "New Zealand" are not independently verified.
The amounts, forms and durations published trials of Desiccated liver actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Typical retail serving
3–6 g
Dried liver powder, roughly 4–8 capsules daily
Equivalent to somewhere between twelve and twenty-five grams of fresh liver. There is no trial establishing a dose; the relevant number is not efficacy but the retinol, copper and iron it carries, which products rarely quantify.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
Taken with meals for tolerability and because retinol is fat-soluble. No timing comparison has been published.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Liver is dense in B vitamins required by energy-producing pathways, which is a nutrient fact rather than a demonstrated effect on fatigue. No trial has tested desiccated liver for energy in people who are not deficient.
Not enough evidence. Not enough human research to say anything useful yet.
Liver supplies heme iron, which is absorbed considerably better than the non-heme iron in plants, alongside vitamin B12 and folate. That nutrient content is well documented; whether capsules of dried liver improve iron status has not been tested in a controlled trial.
Not enough evidence. Not enough human research to say anything useful yet.
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Too much
Liver is the densest common source of retinol, and drying concentrates it roughly fourfold. A daily capsule serving can supply several times the recommended intake and approach the tolerable upper limit, on top of whatever else is in the diet. Chronic excess causes headaches, hair loss, bone thinning and liver damage. Stacking desiccated liver with a multivitamin or cod liver oil makes this considerably more likely.
Avoid
High intakes of preformed vitamin A in early pregnancy are associated with birth defects, which is why pregnant women are advised to avoid liver as a food in the UK and elsewhere. A concentrated liver capsule is the same exposure in a less visible form.
Worth knowing
Liver is very high in copper and in readily absorbed heme iron. That is a problem for anyone with haemochromatosis, Wilson's disease, or simply a high iron status, where extra absorbed iron accumulates rather than being excreted. Men and postmenopausal women rarely need supplemental iron at all.
Worth knowing
The liver is the organ that processes what an animal is exposed to, so residues and metals matter. Country of origin, farming system and any published contaminant testing are the relevant questions, and most brands answer none of them beyond a marketing phrase.
Worth knowing
Liver is not classed among the tissues of highest BSE risk, but bovine sourcing generally remains a live question for anyone who wants it to be. Products from countries with documented BSE controls and traceable herds are the reasonable answer.
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.