Don’t be fooled by the study which found lower cancer rates in vegetarians
Posted on 1 July 2009
I saw this morning reports on a study which has found links between vegetarianism and a reduced risk of certain cancers. The study, which assess nutritional habits and cancer risk in more than 61,000 men and women in the UK found that compared to meat-eaters, vegetarians had a 53, 45 and 74 per cent reduced risk in bladder, blood and lymph system (eg. leukaemia and lymphoma) and stomach cancers respectively [1]. Looking at all cancers combined, risk reduction was found to be 12 per cent. Something tells me that those keen on the vegetarian way will wave this study around as yet more ‘proof’ that the vegetarian diet is healthiest for us.
I do not dismiss this evidence out of hand, but I think it is important to bear in mind that this study was epidemiological in nature, and can only then tell us about associations between diet and cancer. But just because two things are associated does not mean one is causing the other. The usual assumption with studies of this nature is that there
Published July 1, 2009 . Filed under: Healthy Eating, Specific conditions, Unhealthy Eating!
It’s impossible to know what the research means without reading the primary research reports. You are right that researchers need to control for confounding or covarying variables. But your suggestion to only look at people who are “health conscious” risks restricting the range of overall variability – and you won’t get any relationships at all.
Also the classifications of “meat eaters” and “vegetarians” are artificial. Better to measure either the amount of meat (or fish) the subjects eat or the amount of animal protein the subjects eat. Furthermore, vegetarians or vegans have usually not been so since birth – so they may have lived many years as meat-eaters.
This does not invalidate all the research; it only makes it difficult to assess by looking at secondary research reports.
July 1, 2009 @ 11:04 pm
My main concern with this report is that the classification of “meat eater” contains a lot of different types of meat eater.
There is a huge difference between those relying on processed meat from industrially made sausage, pies, ready meals, and those buying meat only from free range, grass finished animals direct from the farm also eating organ meat regularly.
We may be just looking at the effect of a high omega 6 intake compared with a high omega 3 intake.
In the same way the classification of vegetarian includes the full range of those existing solely on industrially processed vegetarian meals to those making their own meals from organically grown fresh vegetables straight from the garden.
July 2, 2009 @ 9:28 am
[...] Correlation is not the same as causation. That’s basically what Dr. Briffa said on his blog: Don?t be fooled by the study which found lower cancer rates in vegetarians | Dr Briffa’s BlogI do not dismiss this evidence out of hand, but I think it is important to bear in mind that this [...]
July 3, 2009 @ 2:16 am
Surely we all have exactly the same Risk of Mortality in that we are all going to die, so what exactly does that mean? Some people die young and others linger on for many sad years in nursing homes.
Virtually no-one will have followed the same dietary plan for the whole of their lives.
These studies make headlines, but seem to have very little substance, other than an axe to grind.
I think that a vegetarian lifestyle must be so boring and fraught with flatulence and prohibitions,that it would just seem to be longer. Give me a nice steak any day, I`ll take my chances!
July 3, 2009 @ 9:54 am
Sherry
‘Risk of mortality’ refers to risk of death over a given period of time.
I’m with you on your sentiments regarding steak.
July 3, 2009 @ 10:00 am
‘Meat eater’ is too general a term. Wild/organic lean meat and oily fish is a different kettle of fish (sorry) than pies and sausage rolls.
Also if people eat meat they may eat fewer vegetables. Is the change in risk associated with the type of meat? The quantity of meat? Or is it that meat eaters consume far fewer vegetables. So if you could get the meat eaters to eat the same quantity of veggies as the vegetarians would this change the results?
We should probably all eat more veg and don’t need to eat as much meat, but I don’t think this makes the case for giving up meat altogether.
July 4, 2009 @ 1:49 pm
[...] Tim Key of Cancer Research UK at Oxford University
July 8, 2009 @ 11:26 am
With reductions of 53, 45 and 74 per cent for bladder, blood and lymph cancers respectively, yet an ovreall reduction in cancer risk of only 12 per cent, it follows that figures for some cancers must inevitably be much lower. In fact there must be some cancers where the risk must be higher in vegetarians than in meat eaters. The break down of the figures for all forms of cnacer would make interesting reading.
My suspicion is that meat per se isn’t the problem but that processes foods in some shape or form are – not all meats are equal just as with carbs and fats. It might also not be the inclusion of meats in the diet that is the problem but the inclusion or exclusion of something else.
The study has highlighted the biggest reduction in risks – fair enough, but some explanation of the disparity between those high percentages and the much lower reduced risk for all forms of cancer requires an explanation. The report might also have said ” vegetarians show reduced risks for x,y and z cancers and increased risk for a, b and c. This presumably might help to identify other factors at play – one of which may be statins or low cholesterol levels for example.
Paul.
July 8, 2009 @ 5:28 pm
[...] não tenha muita crença nestes estudos, que são, por regra, resultado de epidemiologia muito rebuscada e tendenciosa. Quanto à associação entre gorduras totais e mortalidade cardiovascular, ela [...]
July 11, 2009 @ 7:44 pm
Agree with the others. meat can be an indicator for a crap diet full of processed foodlike substances or an indicator for a primal diet full of healthy Real Foods, which will undoubtedly have differing health consequences.
I’m all for a vegetarian diet so long as you add plenty of meat and fish . . .
July 12, 2009 @ 8:51 pm
It all depends on what the vegetarian eats. A vegetarian can live on doughnuts and coca cola. I knew one who never ate fruit or veg while many meat eaters eat these in abundance. Hilda Glickman
July 17, 2009 @ 8:19 am
It wasn’t long ago that most people thought vegetarians would die young or be unhealthy.
July 19, 2009 @ 8:15 pm
[...] tem menos cancro que carnívoros e vegetarianos, e o mais provável é que vegetarianos só têm menos cancro que carnívoros pelo estilo de vida que seguem, e não propriamente por não consumirem carne, e/ou então pelas carnes [...]
March 20, 2010 @ 5:50 pm