Organ meats, bone broth and the forgotten parts

There is an image many of us carry from childhood. Liver with onions on the table. The smell drifting through the whole flat. And at least one person pulling a face.

Maybe you were that child. Maybe you cook for yourself today and still would never buy a beef liver. That is not a quirk, it is a shift across two generations.

In my consultations beef liver still comes up regularly, usually from two directions. Some people have read that liver is the most nutrient dense food there is. Others have heard that liver is dangerous. Each group has not read the other half. The same goes for bone broth. I bring both worlds together here, with numbers instead of adjectives.

How we shrank from the whole animal to one muscle cut

Ask your grandmother what she cooked on Sundays. Often the answer is tongue, kidney, heart or liver dumplings. Ask her great grandchildren the same question. The answer is chicken breast.

What lies between those two answers is not a medical insight. It is refrigeration, prosperity and the self service aisle. Organ meats spoil quickly, smell strong and need craft. Muscle meat can be portioned and standardised. It simply fits an industry better.

How far the retreat has gone shows up in a footnote of official statistics. Since 2022 the German meat supply balance assigns by-products to the carcass, and a separate balance for offal no longer exists. The category has lost its place in the bookkeeping.

This text continues another one. The article on meat, cancer, origin and processing is about which meat was processed how. Here we look at the question before that: which parts still appear at all. The Paleo and AIP perspective picks this up too, usually without the safety side.

What is in liver, and why the number is almost uncomfortable

I pulled the values straight from the nutrient database of the US Department of Agriculture so you can check them yourself. Raw beef liver against lean beef steak, per 100 g. The calorie content is almost identical, 135 against 131. Everything else is not.

USDA FoodData Central, SR Legacy, fdcId 169451 and 174055, queried on 20 August 2026. European values may differ, especially for vitamin A.

Picture the liver as a warehouse and the muscle as a workshop. The liver stores, processes, distributes. That is why the fat soluble vitamins, the copper and the vitamin B12 sit there. A warehouse always holds more than a workshop.

Two points of context. The iron in liver is largely heme iron, and everything about that sits in the article on iron absorption. And these vitamins are not numbers for their own sake, they are cofactors in energy metabolism, see the piece on the cofactors between calorie and energy.

The limit that comes with that density: vitamin A

Here comes the part that enthusiastic liver pages usually leave out. Not out of bad intent, but because it complicates a nice story.

The same vitamin A that makes liver so valuable is a storage compound. Fat soluble, not easily excreted, with an upper limit. The European food safety authority reviewed it in 2024 and kept it at 3,000 µg retinol equivalents per day, for adults, explicitly including women of childbearing age.

So one serving does not sit just below the limit, it sits two thirds above it. And now the sentence that appears almost nowhere in the popular guides, even though you can read it in an agency document.

Once a month or less. Not once a week. The weekly rule circulates everywhere, yet I find no agency source for it. No scandal, just a number that took on a life of its own.

A second safety thread concerns men and older people. In a Swedish cohort of 2,322 men followed over thirty years, the highest fifth of serum retinol showed a rate ratio of 1.64 for fractures and 2.47 for hip fractures, while beta-carotene showed none. A meta-analysis of 13 studies confirms the direction and makes the finding smaller: hip fractures yes, relative risk 1.29, overall fracture risk no.

Copper, purines and the question of where the animal lived

Vitamin A is the best known limit, but not the only one. As far as I can see, nobody does the arithmetic on the second one.

Copper appears on the plus side in almost every text about liver. It sits in enzymes of energy metabolism, in iron metabolism and in connective tissue. All correct. Except that 100 g of beef liver contain 9.755 mg of it.

The third limit is called purines and concerns only some people. A Japanese research group analysed 270 foods by HPLC: chicken liver 312.2 mg total purines per 100 g, pork liver 284.8 mg, beef liver 219.8 mg. The frequently cited daily recommendation for gout prevention sits under 400 mg. A 150 g serving of chicken liver fills that account on its own.

One nuance belongs here, otherwise this turns into a blanket verdict. In a prospective cohort of 47,150 men over twelve years, meat and seafood raised gout risk, while purine rich vegetables and total protein intake did not. So purine is not simply purine, and protein as such is not the issue. How much of it makes sense sits in the article on how much protein you need.

And now you know why with organ meats I talk more about origin and frequency than about the amount on the plate.

Why a carrot is not the same as liver for some people

At this point almost everyone says: then I will just eat carrots, there is vitamin A in those too.

Sort of. A carrot contains beta-carotene, a precursor. Your body has to convert it into retinol first, and for that it needs the enzyme BCMO1. Picture a factory hall where raw material becomes product. Some people have a fast hall, some a slow one. That is partly genetic.

This is one of the lenses that interests me most in integrative work: the genetic one. It explains why two people eating the same way can have different blood values. More on that in the article about genes, ancestry and metabolism.

Glycine and methionine: the balance few people talk about

Now comes the part that fascinates me most professionally and where I also have to phrase things most carefully.

When you eat a steak, you eat muscle. When your grandmother cooked a soup with shank, rind and cartilage, she ate connective tissue along with it. Biochemically those are not the same food. Their amino acid profiles differ, and not by a little.

Glycine is the smallest amino acid there is, and in collagen it occupies every third position of the helix. It is also needed for heme, creatine, bile acids and glutathione. Picture glycine as a person standing in four queues at the same time. That works as long as there is enough of it.

Why is that more than playing with numbers? Because methionine sits abundantly in muscle meat and glycine mostly in connective tissue. A review classes glycine as conditionally essential and names glutathione as the main consumer, see the article on glutathione and detoxification.

A second image is almost too neat. Cheetahs in captivity are fed muscle meat, while in the wild they eat whole prey. A South African group supplemented ten cheetahs with glycine for four weeks in 2025, after which certain metabolic pathways shifted measurably. The authors themselves call the health relevance unknown. Ten big cats are an illustration, not a proof.

In humans there is so far one well conducted but very small study. 24 older adults received glycine plus N-acetylcysteine or placebo for 16 weeks, after which glutathione levels, oxidative stress and physical function improved. One centre, small sample, combination product. That proves nothing for glycine alone and nothing for bone broth.

Bone broth: what is in it, what gets oversold, and the open lead question

Maybe you have seen a jar of bone broth for seven euros and wondered whether that is a food or a supplement. The answer decides which expectation is reasonable.

What is actually in it: during long cooking, collagen from bones, cartilage and skin breaks down into gelatine. That is why a good broth gels in the fridge. Gelatine consists largely of glycine and proline. That is the measurable core of the story.

And the minerals? A Taiwanese group looked at this under controlled conditions. Lowering the pH from 8.38 to 5.32, meaning the classic splash of vinegar, raised calcium and magnesium extraction by a factor of 17.4 and 15.3 respectively, and cooking times beyond eight hours did the same. Even so, both stayed below five percent of the daily intake per serving. The vinegar trick works measurably, it just does not change the order of magnitude.

Two findings that often get told too big belong here for fairness. In a mouse model of chemically induced colitis, pre-treatment with beef bone broth reduced histological damage: a possible mechanism, not an argument for people with bowel disease. And the famous chicken soup study from 2000 slowed the migration of neutrophils in a chamber in the lab, not in a person with a cold.

Collagen: the myth, the peptides and the sober meta-analysis

The idea is seductive and printed on many packages. You eat collagen, it travels into your skin, your wrinkles get fewer. Digestion does not work that way.

Collagen is a protein and gets taken apart like any other. A brick house you transport does not arrive as a house, it arrives as bricks. What gets built from them is decided by the building site, not by the transport. Except that the findings are now finer than that picture.

For joint complaints there are several positive randomised studies. 139 active people with knee problems took 5 g of collagen peptides for twelve weeks, with a significant improvement in activity related pain. Of 147 randomised athletes, 97 remained evaluable after 24 weeks on 10 g of collagen hydrolysate, and six pain parameters improved in them. And in 131 postmenopausal women the T-score rose slightly over twelve months, while it fell in the control group.

If I stopped here, you would have read an advertisement.

One piece of transparency I consider important. Several of the positive collagen studies come from the same constellation, the University of Freiburg together with a collagen research institute in Kiel. That does not make them wrong, but it belongs in the assessment.

For skin the picture looks more robust. Three independent meta-analyses with 19, 26 and 14 studies found improvements in skin moisture and elasticity compared with placebo. The largest one names several risks of bias itself. Almost all participants were women, and the endpoints are device measurements.

What makes sense if you never want to become an offal eater

Maybe you have read this far and are thinking: nice, but I am still not buying liver. Completely fine. Disgust is a real signal, and eating against yourself is rarely a good idea.

The way out is a change of perspective. Do not think in foods, think in nutrients. Liver is not a magical unit, it is a bundle of six or seven things, and you can get most of them elsewhere.

If instead your curiosity is piqued, small portions and long gaps are the whole trick. This is not about a superfood, it is about the quality of what sits on the plate. That is also what the articles on unprocessed food, the calorie myth and omega-3 from plants, animals and algae revolve around.

In my consultations I see a recurring pattern. People arrive with a yes or no question about liver and leave with a different one: what does my own course look like, which values do I know, which stage of life am I in right now. No blog article can do that sorting for you. If you would like to discuss it in person, you will find the option to book an appointment below this article.

And now you know why the forgotten parts of the animal are neither a superfood nor a risk, but a food with very clear instructions for use.

Common questions about organ meats, liver and bone broth

Where this topic leads next

Organ meats and bone broth touch on more than the question of what sits on the plate. They lead to the liver as an organ, to connective tissue, to the fat soluble vitamins and to glycine in entirely different contexts. Here are four ways out of this article.