Coronary Heart Disease

In our brave new world, where questioning authority and searching for truth are championed as positive attributes, it is ironic that we tend to follow predictable behaviour patterns when faced with new information. Decisions which we consider to be impartial, or opinions that we hold about controversial issues based on evidence, balance and facts, may prove to be anything but when scrutinised further.

Take, for example, the preponderance of media articles suggesting that meat and dairy consumption are unhealthy – for us, the animals and the planet. One of the most recent, a plea from film-maker and deep-sea explorer James Cameron, plays upon three phenomena relating to decision-making – cultural cognition, bad news bias and confirmation bias.

We assume that we make impartial, balanced decisions, but we’re far more subject to bias than we may think. Graphic from Capper (2017) Cattle Practice.

Celebrities have been used to sell products, messages and ideologies for centuries, from the Royal Family endorsing Wedgewood pottery in the 1760s, to Bette Davis advertising shampoo in the 1950s and Joanna Lumley now gaining publicity for activist causes. However, fame doesn’t imply any degree of expertise, knowledge or understanding of the issue, just a belief that the solution lies with X, whatever X might be.

Most of us aim to be like our heroes, whether they are famous based on appearance, acting ability, athletic skill or career prominence; thus we are prone to cultural cognition. If I believe that celebrity A believes that something is right/wrong and I aspire to being like this celebrity, I am more likely to adopt their message without question. The fact that a famous Hollywood film maker (and deep-sea explorer – seriously, who doesn’t aspire to be a deep-sea explorer?) has sufficient belief to write an op-ed in The Guardian claiming that we should all reduce meat and dairy consumption, therefore resonates with us far more highly than the same message from a non-famous individual.

The inevitable “this is killing us and the planet” rhetoric adds an extra layer of credibility via bad news bias, in that we are preconditioned to believe negative news over positive news. “Bad news sells” is clichéd, yet true (and explains the popularity of “X Causes Cancer” stories in the Daily Mail) and we need five pieces of positive information to negate each piece of negative information.

Confirmation bias is the final layer in this anti-meat and dairy club sandwich. It’s difficult, if not impossible, to have missed media coverage of potential impacts of meat and dairy consumption on health. If we consciously (or subconsciously) absorb the message that these foods are bad, then Cameron’s claims that “eating too much meat and dairy is making us sick, greatly increasing our risk of heart disease, type 2 diabetes, several major cancers (including breast, liver and prostate) and obesity” agree with our existing bias and we are likely to believe them. However, these claims do not accord with (nor are linked to) current scientific literature on dairy consumption.

This would include, for example, a meta-analysis in Breast Cancer Research and Treatment, which demonstrated a negative association between dairy consumption and breast cancer, i.e. increasing dairy product consumption may be associated with a reduced risk of breast cancer. In addition, a dose-response meta-analysis in the European Journal of Epidemiology reported neutral associations (i.e. no clear positive or negative association) between dairy product consumption and cardiovascular and all-cause mortality. Perhaps even the recent article in Nutrition Research Reviews, which concluded that recommending reduced dairy consumption in order to lower saturated fatty acid intakes (and thus the risk of type II diabetes and cardiovascular disease) would have limited, or possibly negative effects.

Ice-cream (and other dairy products) may reduce the risk of breast cancer.

When the subject under discussion is the fictional lives of blue-skinned human hybrids (as per the film Avatar, directed by Cameron), it’s perhaps easier to use imagination than rely on scientific veracity. However, having an evidence basis for claims made in media articles is increasingly important, especially when the claims are made by those who are only prominent for their excellence in other (non-scientific) areas.

In the meantime, eat, drink and be merry over the next two weeks – content in the knowledge that clotted cream with your mince pie will not have adverse health effects, and may even prevent against cancer. Merry Christmas and a Happy New Year!

I know Harvard researchers are smart, I really do. Yet I have to question the latest study reporting that eating red meat is associated with premature death. Published in the Archives of Internal Medicine, the paper analyzed the relationship between mortality and red meat consumption in a total of 121,342 healthcare professionals and concluded that:

Greater consumption of unprocessed and processed red meats is associated with higher mortality risk… replacement of red meat with alternative healthy dietary components may lower the mortality risk.

As a researcher, I know full well that it’s almost impossible to prove a cause-effect relationship. This is particularly difficult in human studies where other dietary and lifestyle factors have to be accounted for. After all, if you have ketchup on your steak, does the lycopene prevent against prostate cancer? “Associated with” is therefore absolutely the correct terminology for the paper’s authors to use. Alas, in the minds of so many, “associated with” translates to “causes” (especially when it’s a bad news story), and everybody panics accordingly.

The results of this report need to be put into context with our other lifestyle choices. If, as reported, eating unprocessed or processed red meat increases the relative risk of mortality by 13% and 20% respectively, how does that compare to all our other daily activities – driving a car, drinking a glass of wine or eating a candy bar? How do we weigh the risk of consuming a steak or slice of pepperoni pizza against the bottle of Mountain Dew or unwashed raw carrot? After all, during the BSE crisis in the UK, data suggested that the risk of dying from falling out of bed and suffering a fatal head injury was far greater than that from contracting vCJD, yet there was immense consumer concern relating to the perceived dangers of beef consumption.

Relative risk is not a measure that many people understand. Within this study, the absolute mortality risks (i.e. the probability of any one person dying) paint a rather different picture. Out of every 100 men, 1.23 men consuming three servings of unprocessed meat (the equivalent of one 9-oz steak) per week were likely to die, versus 1.30 men eating 6 oz of processed meat (bacon, sausage etc) per day (42 oz per week). Given the small difference in those mortality risks (which were similar for women) yet the huge difference (9 oz vs. 42 oz) in weekly meat consumption, we would be better served by focusing more on other factors (bodyweight, exercise, genetic propensity to specific diseases) that contribute the vast majority of our absolute mortality risk rather than assuming that we can live forever if we only replace a hamburger with a vegetarian meatloaf.

Since this study hit the headlines my Facebook newsfeed predictably been over-run by anecdotes about grandparents who lived to the ripe of age of 101 years while eating bacon and eggs for breakfast, corned-beef hash for lunch and three pork chops (with extra heavy cream in the whipped potatoes) for dinner. Without wishing to be flippant, the one certainty in this life is that we’ll all die at some point – if I restricted my meat intake to the suggested 3 oz per day (or less) I have a sneaking feeling that I might not live forever, but it’d sure feel like it.