What is red meat

Does it have a scientific definition?

Health, environmental and ideological objections are regularly levelled against our evolutionary super-fuel, red meat. What once provided the energy and the nutrients for expanding our brain size, and for us to be us, is now vilified. So, if red meat is bad, how is it defined?

For example, is it defined by its colour — red? Are duck, tuna, sardines and chicken livers red meats? How red does it have to be — is pork (marketed in Australia as ‘that other white meat’), rabbit or goat red meat? What about pink (salmon)? The light and dark meat of chickens?

The World Health Organisation (WHO) avoid these conundrums (while creating others) by using a taxonomic definition for red meat.

The WHO definition

The WHO provided this definition for red meat in their high-impact but discredited 2015 report claiming a probable link to colorectal cancer (CRC): ‘Red meat refers to all mammalian muscle meat, including, beef, veal, pork, lamb, mutton, horse, and goat.’ This might be the US Department of Agriculture definition as well (although I haven’t been able to confirm that directly — the USDA definition, if there is one, is conspicuous by its elusiveness).

So, red meat = mammal meat. The definition of red meat is based on a taxonomic Class (Mammalia), and not on meat colour.

Rabbit, kangaroo, venison and other game are, therefore, red meat. Note the inclusion of ‘muscle’ in the WHO definition. Therefore, beef/lamb kidney and liver are not red meat because they are not muscle, despite being deeply red and coming from mammals. Everything that is not a mammal is not red, regardless of its colour — for example, birds with red flesh (duck, emu, quail), other reptiles (crocodile, turtle), amphibians (frogs), and all seafood and fresh-water fish (including animals with red flesh such as tuna, but excluding sea-going mammals such as whales and seals).

The rationale

The WHO did not elaborate on their rationale for this definition. Other definitions exist in the literature, such as all ‘livestock’ (e.g. 4-legged farm animals), or arbitrary lists: e.g. ‘beef, pork, lamb, and goat from domesticated animals’ (American Institute for Cancer Research). A health-based rationale for these definitions is also not to be found — what is the significance of having 4 legs or being domesticated, for example. While there are some commonalities across these definitions, significant differences remain. Without a firm definition of red meat, and a plausible biological basis for that definition, we should go no further.

The mechanism?

The WHO was also silent as to why mammalian muscle might be a risk-factor for CRC, other than to point out that meat contains haem-iron (HI), and imply that HI could be a causative factor without saying so outright. HI is most often alluded to in the literature on whether meat might be harmful. It is an attractive ‘explanation’, because HI is only found in animals, not in plants (plants contain iron but not haem).

HI and colour

The WHO create a new problem by alluding to HI, because HI is found to varying degrees in all animals, not just mammals. It is also present in internal organs such as liver and kidney. As well, HI is what makes meat red (in general more HI means darker red). The conundrum that the WHO create is that red-fleshed non-mammals should also pose a health risk if HI is a risk, and that we should categorise red meat according to its colour, or at least its HI content, not its taxonomy. Furthermore, if their concern about HI is genuine, then the levels of HI in cuts of meat should be provided on food labels and the public educated.

Where does this get us?

We have a definition of red meat that does not refer to red, and a putative explanation that does. This is what happens when there isn’t a sensible definition from the outset — contradictions arise. This makes any conclusions drawn about red meat suspiciously opinion-based rather than scientific.

HI and non-haem iron

I will expand on HI (and non-haem iron) in a separate post — it makes an interesting story, and a relevant one considering the widespread prevalence of iron deficiencies in the population (estimated at 2 billion people worldwide) and the associated health risks arising from that, especially for children.

The final irony

Meat containing HI is one of our best dietary sources of readily-digestible iron.

Further information

The WHO provide a short Q&A of their opinion piece. An good critique of their report has been provided by Georgina Ede , and there are more general comments in a video interview with Nina Teicholz.