"You can never be sure that you've wiped out all of these other confounders that go with eating a lot of red meat, things like being less well educated, eating more fat, exercising less, smoking more," Clifton says. "It's really hard to be 100 per cent sure that it's the red meat that's related to the cancers and death rate, or whether it's something else these people are eating or doing."

So, for instance, a 2007 Japanese study published in Cancer Science found no association between high red meat intake and colorectal cancer. And last month the American Journal of Clinical Nutrition published the results of another 10-year study, conducted by researchers from Oxford University, which found that there was absolutely no difference in mortality rates between meat eaters and vegetarians. Who knows what other factors may have confounded those results?

It might be as simple as the way we cook meat. Overcooking food — especially blackening or charring — produces cancer-forming chemicals such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HAs). But even there the science isn't straightforward. In animal studies, HAs are carcinogenic, but the evidence in human studies is still not clear.

And many in the Australian research community — from leading scientists and nutritionists to Meat and Livestock Australia — are quick to point out that one of the greatest confounders is the nature of the red meat itself, where "red meat" includes beef, lamb and pork.

"We do know that in Australia meat production is very different," says dietician Veronique Droulez, who heads the nutrition research department at Meat and Livestock Australia. "It's very lean and very trimmed. It has much less saturated fat than other countries." (It's the difference between being lot-fed or grain-fed and grass-fed.) "We consume meat quite differently. We eat beef and lamb; in the UK and Europe it's mainly pork. We know that we eat our meat with vegies. And in fact we see that the more red meat we eat, the more vegies we consume."

And studies by both MLA and the CSIRO find that eating red meat as part of a balanced diet — that is, with lots of fruit and vegetables — has a number of beneficial health effects. Indeed, the reason there's such a thing as a recommended intake is that just about everyone agrees eating some red meat is good for you.

Iron and zinc are essential for brain development, and general wellbeing (and iron deficiency is a significant health problem in Australia, according to the National Health and Medical Research Council). Red meat is not only a rich source of those nutrients, it's the one in which they're most "bio-available": that is, our bodies can absorb and make use of them easily and quickly. Red meat is a source of Omega 3 fatty acids, and various other important vitamins and minerals including B12. And just to confuse the issue further, research at the CSIRO has shown that lean red meat is associated with lowering cholesterol — helping prevent, rather than cause, heart disease.

Clifton says the chief problem with red meat "warnings" is that no one has been able to prove causality. "There's actually nothing that we know of in red meat that would actually cause some of these cancers, or general increased mortality," he says.

Professor Ian Olver, chief executive officer of Cancer Council Australia, agrees. "Population studies demonstrate these relationships between red meat and cancer deaths but are not able to prove that one causes the other," he says. "They do however give impetus for further, more specific, research." In the meantime: "The message for consumers is to eat a diet with a balance of all of the food groups, and foods such as red meat in moderation."

Of course, what constitutes moderation is another contentious issue. Clifton recommends 150-200 grams of lean red meat, three to four times a week. The official Australian dietary guidelines suggest 65-100 grams of lean red meat, three to four times a week. Medical journal Lancet recommends 50 grams per person per day. Others suggest as little as 30 grams, twice a week. It seems to depend on how much weight you give to the various negative and positive studies, how conservative you are, or — as one dietician and industry insider put it — "guesswork".

The study by the Royal Victorian Eye and Ear Hospital that established a link between red meat and vision loss found that link in people who ate red meat more than 10 times a week. That's a helluva lot of steak. Report author Dr Elaine Chong said when they looked at the study population, a quarter were eating what most people would consider excessive amounts of red meat — and it was at those excessive levels that problems started to emerge.

Lack of information

IF A quarter of the general population is eating red meat more than 10 times a week, it's no wonder we're getting crook. But for such a red-hot topic, there's surprisingly poor information available about how much red meat we actually consume.

The Australian Bureau of Statistics has data about "apparent" consumption: that is, the amount of meat available on the market. And it's measured in absolute raw weight — before butchering, preparation and cooking (all of which significantly reduce the amount of meat that actually goes into our mouths). Still, there has been a steady decline in apparent consumption in the past 40 years, to a total of 50.7 kilograms per person per year in 2007.

That decline in consumption coincides with a period when Western society started to change in all kinds of ways, including what we ate and why. In Australia we began embracing a more multicultural diet: fewer chops and three veg, more pasta and stir-fries. It was also the time at which ethical and environmental eating first started to gain ground.

Patrick Monaghan stopped eating meat as a teenager, after a violent and memorable bout of nausea. But as a young adult, his commitment to vegetarianism was consolidated by the information he started reading about meat versus veg. "The people I admired — which would have been musicians — were all vegetarians," he says. "The guys in the Clash, Johnny Marr in the Smiths, the only Beatle I thought was worthwhile, George Harrison — all these people who were significant to me culturally were vegetarian. I read about why they'd done it, and it started to make more and more sense to me; that it was an ethical thing to do. It was a better use of the planet."

Monaghan's first experiments with vegetarianism were fairly disastrous. Existing on fruit and vegetables, bowls of muesli, and way too much cheese, he was in hospital with gallstones by the time he was 22. These days he has a better handle on what he needs to eat to stay healthy, and the rash of research about the perils of eating meat do provide a sense of affirmation. "Validated," he says, "with the occasional hint of smugness."

And even among committed carnivores, the various health warnings do have an impact. "The most telling medical research I read was not about meat especially but just that we're eating too much food," says Nick Bastow. "I had a T-bone steak for the first time in ages the other day and it was just gigantic. I looked at it and thought, that's just ridiculous. How did we ever eat that on a regular basis?"

Bastow continues to eat meat because he likes the taste, and because he likes the culture. He's a huge fan of the old-fashioned butcher shop, the skill involved in preparing meat well, and the meat culture that's still alive and well in Melbourne's ethnic communities. Food is, after all, more than just fuel. "But I intrinsically have this feeling that meat is good for me, too," he says.

Bastow estimates he would eat "less than a kilo" of meat a week. The last detailed survey of actual consumption was in 1995, when we were eating about 600 grams a week for men and 300 grams a week for women. Which is about what at least some of the experts recommend.

Tony Stewart is probably typical of the educated, middle-class meat eater — and the reason the Australian scientific community remains largely sanguine about current negative studies. Like most of us, Stewart grew up eating meat, and still considers it "the fundamental backbone of food".

"I think it's probably healthy, and without it a meal doesn't seem complete," he says. But meat doesn't necessarily mean red meat, meat isn't on the menu every day, and the quality of what he and his family are eating — in terms of its provenance as well as its taste — is important.

Stewart's interested in the research, but not panicked by it. "The links between smoked or processed meat and cancer have had an effect," he says. "Ham, salami, smoked chicken, all these things, I'm a bit conscious of not overdoing it. But moderation and variety is my motto, as far as food goes."

The thing that bothers him most about eating meat — and he's not alone — is the idea of the slaughterhouse. But there's a big difference between believing meat is murder, and believing it's murderous.

The abattoir effect

STEWART Truswell, emeritus professor of human nutrition at the University of Sydney and a member of the editorial panel that reviewed Meat and Livestock Australia's report on the role of red meat in diet, doesn't like to think too closely about what goes on in an abattoir. "It's a horrible thought. And I have no problem with vegetarians, I respect their position," he says. "I just don't think the vegetarian argument that meat is bad for your health is anything like as good as the ethical and humanitarian arguments."

As an elder statesman of Australia's scientific community, Truswell has followed many research controversies, and considers the argy-bargy over red meat just another in that long line. It's all part of the scientific process. "These storms in teacups will come and go," he says. "But really, we'll be eating red meat until …" He can't bring himself to say "until the cows come home". But we know what he means.