Professor Mike Archer is well known for his advocacy of eating kangaroos. Just before Christmas, Archer penned a singularly provocative article on “The Conversation” called: Ordering the vegetarian meal? There’s more animal blood on your hands”. I’ll discuss the article more generally in a separate post, but for the moment I want to focus on some health claims for kangaroo meat that were made in comments following the article by both Archer and colleague Rosie Cooney from UNSW.
You can say what you want in a blog, but has anybody seen a label on packaged kangaroo meat saying “This meat has anti-cancer properties”?
No? Of course not. Health claims on packaging are regulated by law and require evidence. Consult the Food Standards Australia website for details. The legislation is currently under review. It isn’t brilliant, but it does have a few teeth. You don’t see those labels on kangaroo meat because there isn’t any evidence that it has any cancer fighting or prevention properties.
On the other hand it is the judgement of the 150 expert scientific authors of the World Cancer Research Fund’s 2007 report that red meat causes bowel cancer. No ifs, no buts, no caveats. It probably causes other cancers also, but the causal link with bowel cancer has been convincingly shown. Professor Graham Giles of Cancer Council Australia has estimated the PAF (population attributable fraction) of Australia’s new bowel cancer cases due to more than 1 red meat meal per week as 48 percent based on his team’s analysis of the Melbourne Collaborative Cohort of over 40,000 people (personal communication based on his teams input to the WCRF process). This is over 6,000 new cases of bowel cancer every year due to red meat.
Kangaroo meat is red meat and its high heme iron content makes it likely, but not certain, that it is an even more potent cause of bowel cancer than other red meats. Given Australia’s world leading position in bowel cancer rates and the predominance of grass fed beef on the local market, the common bleating of US organic grass fed meat propagandists that it is only grain fed meat that can possibly be bad for you is total rubbish.
If Archer and Cooney want to make health claims about red meat and cancer, any kind of cancer, then the techniques for testing the meat’s capacity to cause DNA damage in colon cells aren’t a secret and UNSW would more than likely have people with the necessary skills. Alternatively, they could send some meat to the UK Dunn Human Nutrition lab for testing. But I’m guessing they are more interested in a “Don’t ask, don’t tell” policy.
Archer and Cooney aren’t just going a little beyond the evidence. It’s pretty clear they didn’t bother to do any basic fact checking before making the claims. Been there, done that, very embarrassing.
Cooney, in her praise for kangaroo meat stated: “I would have thought the extraordinarily high CLA content of kangaroo meat, generally thought to be so anti-carcinogenic, including wrt colon cancer, would have outweighed this sort of damage though.”
The damage she is referring to is the damage found in colon cell DNA after a red meat meal. It isn’t just that such damage has been experimentally confirmed in humans, the damage has been shown to be the same kind of damage that is seen in bowel cancer patients. This involved far more sophisticated science.
Like a poker playing polishing a bluff, Archer saw Cooney’s “I would have thought that”, raised it to “generally thought [that]” and then bet on it as a health reason for eating kangaroo meat. He stated in a comment: “Further, the 2% fat and the extraordinarily high CLA content of kangaroo meat (see Rosie Cooney’s post), generally thought to be anti-carcinogenic including wrt colon cancer, are human health reasons for why this should be the first choice among environmentally-friendly meats for the more discerning omnivores.”
There it is again, CLA levels aren’t just high in kangaroo meat, but “extraordinarily high”! And what the hell is CLA anyway.
What the hell are CLAs anyway?
CLAs are a type of fat molecule found in some plants and animals. You can find pictures of their atomic structure on Wikipedia.
The form found in cattle, kangaroos and other animals is conjugated linoleic acid and that found in some plants is conjugated linolenic acid. Spot the difference? lenic Vs leic. Very subtle. But it gets worse. There are some dozens of types of these molecules which have the same chemical formula but slightly different arrangements of the atoms … such groups are called isomers.
The isomer found in beef and kangaroos is c9t11 CLA. It is indeed being tested for its efficacy in a range of conditions ranging from elevated blood sugar levels through to cancer. The dosages given to humans in such research range from about 1 gram per person per day to over 4 grams and typically the trials can take weeks to see any effect … and sometimes nothing at all happens. To say that this chemistry is way more complex than rocket science or fossils is a grand understatment.
Which brings us to the level of CLA in kangaroo meat. What is this “extraordinary” level? The highest average level recorded in a study commissioned by RIRDC was 17 milli grams per 100 grams of meat with a quite large standard deviation.
So how much kangaroo meat would you need to get a 1 gram CLA dose? About 5.8 kilograms … every day for weeks.
But it gets worse. There is CLA in beef and dairy products also. Which has more CLA? Beef or kangaroo? Again, the devil is in the detail. Kangaroo meat has more CLA than beef meat, but beef fat has more CLA than kangaroo fatand there is more fat in beef meat than in kangaroo meat. Is that clear? The point is that the CLA in a slice of beef may well be similar to that in a slice of kangaroo … despite the roo meat itself technically richer. It’s all in the RIRDC report. So if the CLA in beef doesn’t protect you from bowel cancer, why would anybody expect anything different with kangaroo meat?
Lastly, there is one final nail that needs to go in this coffin. Those pesky isomers. Studies don’t always use the naturally occuring isomer, the c9t11 kind found in red meat and dairy products. It appears that mixing that isomer with another works much better.
So it seems pretty clear that evolution hasn’t miraculously equipped kangaroos to donate a compound to fight the effects on our bowels of eating them. The best available science says kangaroos will at least get some posthumus revenge in the nation’s cancer wards.