Scary stuff, eh?

This image has been made available by Purdue University, with the official caption:

Researchers at Purdue have precisely measured the impact of a high-fat diet on the spread of cancer, finding that excessive dietary fat caused a 300 percent increase in metastasizing tumor cells in laboratory animals. Here, lipid-rich cancer cells (the two round objects) attach to collagen fibrils, simultaneously visualized using coherent anti-Stokes Raman scattering and sum frequency generation imaging. Cancer cells attach to collagen before spreading to organs in the body. (Weldon School of Biomedical Engineering, Purdue University)

As I said, scary stuff. So a high-fat diet causes a 300% increase in metastasising tumour cells in mice? The official press release continues:

"These findings demonstrate that an increase in lipids leads directly to a rise in cancer metastasis." Ji-Xin Cheng of Purdue's Weldon School of Biomedical Engineering and Department of Chemistry.

Then there's:

Results showed the increase in lipids had no impact on the original tumors implanted in the mice. However, the rate of metastasis rose a dramatic 300 percent in the mice fed a high-fat diet.

and:

The researches used the imaging and cell-counting tools to document that linoleic acid, which is predominant in polyunsaturated fats, caused increasing membrane phase separation, whereas oleic acid, found in monounsaturated fats, did not. Increased membrane phase separation could improve the opportunity of circulating tumor cells to adhere to blood vessel walls and escape to organs far from the original tumor site.

What's the truth behind the headlines and the scary graphic?

It's something that has been known for years.

Something that nutritionists and governments alike are not only ignoring, but actively encouraging the world to do.

What is it?

"The new findings support earlier evidence from other research that consuming high amounts of polyunsaturated fat may increase the risk of cancer spreading."

Yes, polyunsaturated fats - those 'healthy' vegetable oils - may help the spread of cancer through the body. The researchers fed the mice on linoleic acid - Omega-6 - a PUFA.

Don't believe me? Read the study here.

How long will it be before Dr Susan Jebb, the Food Standards Agency, and the World Cancer Resarch Fund et al start citing this study as proof positive that we must never, ever, ever, eat saturated fats?

Let's just see, shall we?

Friday and the promised email.

Yes, the email promised by World Cancer Research Fund UK arrived, with the explanation that the science team "has taken into account many different sources as the aim was always to be as evidence-based as possible".

The link provided led me to the actual report, together with a list of 1,028 references.

My first reaction was amazement that there were so many studies on the relationship between red meat and cancer, but I quickly discovered my mistake. The titles of the studies contained in the 1,028 references told quite a different tale. These are just some of them chosen at random:

Taxing snack foods
Effectiveness of physical activity programs at worksites with respect to work-related outcomes
Why don't you grow your own?
Does returning to work after childbirth affect breastfeeding practices?
Government perspective: food labeling
Major factors influencing breastfeeding rates: mother’s perception of father’s attitude and milk supply.
Estimation of food demand patterns in South Africa based on a survey of households.

So I searched for "red meat", and came up with these results:

Tzoulaki I, Brown IJ, Chan Q, et al. Relation of iron and red meat intake to blood pressure: cross sectional epidemiological study. BMJ (Clin Res Ed) 2008;337:a258.
Conclusions: Haem iron showed direct weak associations with blood pressure. Haem iron is found mainly in red meat, poultry, and seafood; it is a major component of total iron intake in Western diets.e
Does this show that red meat causes cancer? Nope! Does it even show that red meat raises blood pressure to a dangerous level? Nope!

van den Brandt PA, Botterweck AAM, Goldbohm RA. Salt intake, cured meat consumption, refrigerator use and stomach cancer incidence: a prospective cohort study (Netherlands). Cancer
Causes Control 2003;14:427-38.
CONCLUSION: The present findings suggest that intake of dietary salt and several types of cured meat were weakly positively associated with stomach cancer risk.
So, does this one show that red meat causes cancer? Nope!

That's it, folks - just two studies with 'red meat' in the title.

So I tried "meat" on its own, and fared rather better! The first 'meat' only study is this one. Its findings are very interesting:

Cordain L, Eaton SB,Miller JB, et al. The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. Eur J Clin Nutr 2002;56 Suppl 1:S42-52.
CONCLUSION: The high reliance upon animal-based foods would not have necessarily elicited unfavorable blood lipid profiles because of the hypolipidemic effects of high dietary protein (19-35% energy) and the relatively low level of dietary carbohydrate (22-40% energy). Although fat intake (28-58% energy) would have been similar to or higher than that found in Western diets, it is likely that important qualitative differences in fat intake, including relatively high levels of MUFA and PUFA and a lower omega-6/omega-3 fatty acid ratio, would have served to inhibit the development of CVD.
So, a high-fat, high-protein, low-carbohydrate, low-polyunsaturated fats diet "inhibits the development" of cardiovascular disease! Yes, but what about cancer? Sorry - no mention of red meat causing cancer!

Next was this, with very interesting conclusions:
CrawfordMA,WoodfordMH, Casped NM. Comparative studies on fatty acid composition of wild and domestic meats. Int J Biochem 1970;1:295-305.
Conclusions: Literature comparisons showed tissue lipids of North American and African ruminants were similar to pasture-fed cattle, but dissimilar to grain-fed cattle. The lipid composition of wild ruminant tissues may serve as a model for dietary lipid recommendations in treating and preventing chronic disease.
Grass-fed cattle should be recommended to treat and prevent chronic disease, but not grain-fed cattle. Why? Because cattle are now being fed soy to make their meat more 'healthy' for humans! This means that what we think of as 'saturated animal fat' is more like plant polyunsaturates.

Then came:

Lazaridis P. Household meat demand in Greece: a demand systems approach
using microdata agribusiness. Agribusiness 2003;19:43-59.
Nothing to do with cancer.

Mata RG, VillalonMFV, Salazar JAG, et al. Econometric model for determining the
factors affecting the swine meat market inMexico. Interciencia 2004;29:214-420.
Hsu L. Gradual structural changes of meat consumption in Taiwan. J Int Food Agribus Mark 2000;11:33-50.
Nothing to do with cancer.

Hsu L. Gradual structural changes of meat consumption in Taiwan. J Int Food Agribus Mark 2000;11:33-50.
Nothing to do with cancer.

Mata RG, VillalonMFV, Salazar JAG, et al. Econometric model for determining the factors affecting the swine meat market inMexico. Interciencia 2004;29:214-420.
Nothing to do with cancer.

By this time I was more than a third of the way through the references, so decided to start searching the document itself for specific references. And can you guess what I found?

"Using the UK NDNS dietary data for 19–64 year olds, exposures for individual red meats (beef, pork, etc.) were aggregated into a single variable (red meat)."

Yes, it's our old friend NDNS 2000-2001 with it's flawed surveys once again! So on what else is the warning based? I've no idea as I've not been able to find anything else, except for confirmation that: "‘Red meat’ refers to beef, pork, lamb, and goat from domesticated animals including that contained in processed foods" (p 382), and the bald, unsupported statement:

Evidence
The evidence that red meat, and particularly processed meat, is a cause of colorectal cancer is stronger now than it was in the mid-1990s.

Much of the report centres on the economy of agricultures, and I encountered such phrases as "All food items (except other red meat) had an inelastic own-price elasticity of demand over the study period.". One such area studied in some depth is the former Soviet Union. That particular section concludes:

"No definite conclusions can be drawn since none of the studies explicitly measured the impact of agricultural policies on dietary outcomes."

Quite!

Tomorrow I intend looking at the other side of the coin - the good that grass-fed red meat does for us, including how it actually protects us from cancer.

Footnote: I'm now told by the WCRF press officer that the "advice on red meat comes from the companion report to this report, whichwas published in 2007" which is on this link. I've yet to find it, but if I do I'll post it!