This post (Bacon Cancer) will explain what we know and what we don’t know about eating meat as a cause of cancer. The following post (Meat Cancer Prevention) will take a practical approach: what we can do to minimize our risk, without removing all the joy (and nutrition) from our diets.
Now WHO is the Party Spoiler?
According to the World Health Organization, our holiday feast abounds with carcinogens from meats:
– Perhaps you have a red-blooded main course: standing rib roast, pork roast, ham.
– Perhaps your main gobbles and waddles – but is there pork sausage in that turkey stuffing?
– How about the sides? My baked potato wants butter, sour cream and bacon, if you please.
Even an un-stuffed turkey brings dangers, if it’s smoked. click to show bad joke
The idea of cancer from bacon – in fact, cancer from meats of all kinds – is pretty alarming. After all, Bacon is one of the four pillars of the ideal American Diet (the other three being of course Chocolate, Wine and Cheese). So WHO caused a terrible fuss a few weeks ago when they announced the results from a meeting of 22 scientists from 10 countries, meeting in Lyon, France. They had reviewed 800 research studies relating cancer to human food consumption and concluded that:
(1) processed meat definitely causes cancer; and that
(2) all red meat may cause cancer.
Bacon Cancer: Panic and Ridicule
The WHO announcement was followed by a flurry of headlines:
– Chicken Little sky-is-falling alarms (The Guardian: Processed meats rank alongside smoking as cancer causes)
– Puritanical finger-wagging (Slate.com: Do Bacon and Red Meat Cause Cancer? You can’t always eat what you want)
– Passionate denials (Financial Times: A false alarm on red meat and cancer)
The most biting barbs came from that bastion of thoughtful journalism, the New York Post:
…let’s say the scarier numbers mentioned by Cancer Research UK are correct, and eating meat causes 10 additional people in a thousand to get bowel cancer. Ten in a thousand equals one in a hundred. That’s all you get for the expense, difficulty, preparation time and perpetual buzzkill of being a vegan?
One in a hundred for being the guy who brings the sad quinoa patty to every tailgate and insists, “But this is the FIRM kind of tofu” at every barbecue?
One in a hundred for being the dietary pain in the ass your friends mocked behind your back at the epic Five Napkin Burger outing to which you weren’t invited?
One in a hundred for being a lifelong prosciutto-prohibitionist, pepperoni-punter and pâté-pooper?
Homer Simpson is laughing so hard he is choking on his baloney, liverwurst and olive-loaf sandwich.
Bacon Cancer: Just the Facts, Ma’am
When the WHO announcement came out I knew that I wanted – no, needed – to blog about it. However, the subject turns out to be fiendishly complicated. Every news article takes a different angle, and the twenty research articles cited by WHO often present contradictory conclusions.
After reading more than fifty articles I have boiled down the data for you. However, I couldn’t fit it into a single blog – hence, this blog on Bacon Cancer, plus the following one on Meat Cancer Prevention.
The plan truth is that cancer in humans is very poorly understood, and difficult to even study: it’s relatively rare and slow to develop; it depends on heredity, environment, diet, behavior and other factors; and you can’t run the same comprehensive studies on people as you can on, say, rats.
What science understands about cancer and cancer prevention is a patchwork of several kinds of inconclusive research work:
– Epidemiological studies look for correlations between what people eat and the kinds of cancer they may or may not contract. Cancer is sufficiently uncommon that a study may need to look at fifty or a hundred thousand people, and study them for fifteen or twenty years! But just showing that eating something is correlated with acquiring a certain kind of cancer does not show causation. Even after correcting for all the factors you can think of (exercise, social status, other health conditions, and so on), any apparent link might always be due to some factor that you haven’t thought to exclude.
– Animal researchers use control populations for comparison, so you can be sure that when your test group gets cancer, it’s due only to the single factor that you are studying. But questions still persist. Cancer is still rare enough that you need rats that are either genetically susceptible, or are treated with chemicals that make them vulnerable to cancer; otherwise, you wouldn’t collect statistically significant data during the researcher’s lifetime (or, more likely, during the tenure of the grad student who may be doing all the grunt work). In addition, although some people may be rats, rats are not people, and what we learn about cancer in rats does not automatically apply to humans.
– Molecular biology looks at suspected carcinogens and traces the many steps that lead to an actual cancerous tumor. However, stopping cancer is not a matter of killing a single strain of bacteria or viruses. Cancer is a group of diseases involving abnormal cell growth; a given tumor may arise from multiple causes and may involve multiple malfunctions within the cell. It’s seems that you can’t thoroughly understand cancer, an abnormal manifestation of life, without understanding life itself.
Organizations that try to understand and defeat cancer have to look at the results from many different studies and make sense of them. This involves guesswork, and hypotheses as to the mechanisms that are most important. Given the uncertainties in the research data and the complexity of the problem, perhaps it’s not surprising that there’s disagreement about such basic questions as, what should we do, and what should we eat, to avoid “bacon cancer” and achieve optimum health?
Bacon Cancer: Categories of Meat
There are so many kinds of food, and cancer is so rare, that it’s not practical for researchers to study the health effects of every individual food. Therefore, they group the data for foods that are expected to behave in similar ways, in order to learn the basic causes of cancer. Where meat is concerned, here are the definitions most commonly used when discussing carcinogens:
– Red meat means muscle meat from mammals: beef, veal, pork, lamb, mutton, goat and horse. (yes, I’m sorry, that is WHO’s list)
– White meat means the flesh of fish and poultry.
– Processed meat means meat treated by salting, curing, fermentation, smoking or other processes for flavor or preservation; the principal ingredient is often, but not exclusively, red meat.
Some studies of the causes of cancer deal with very large data bases. Thus researchers can look within these groups and tease out differences in carcinogenicity between, say, beef and pork, or between fowl and fish. The differences tend to be minor, and not very consistent from one study to the next. For example, some studies show that eating fish is weakly protective against cancer but eating poultry is not; however, other studies show just the opposite, or no difference at all.
Eating Meat is Much Less Dangerous than Smoking
A good entry point for understanding bacon cancer and other food-caused cancers is tobacco smoking.
After years of research by thousands of scientists, battling tobacco companies all the way, it’s now well known that smoking causes lung cancer. And we have a simple way to think about why that happens: burning tobacco creates poisonous chemicals that are carried in the tobacco smoke; those chemicals are inhaled and fill the delicate alveoli within the lungs; they irritate those tender tissues and cause the cells to go rogue, mutating into cancer cells. That is not the whole story, of course, but it’s a fair approximation.
Just as smoking causes cancers in the respiratory tract (lungs, mouth, throat), eating can cause cancers in the digestive tract (esophagus, stomach and intestines). But there are some key differences between smoking and eating:
– Eating is much less dangerous than smoking. Thanks to millions of years of evolution, our bodies are well equipped to process food without suffering ill effects; that’s one reason that digestive tract cancers are less prevalent than smoking-caused lesions. Nevertheless, colorectal cancer (the principal digestive cancer) is still worth preventing, since it’s the third most common cancer worldwide, behind lung and breast cancer.
– Food changes much more within the body than smoke does. Tobacco smoke does not undergo much chemical change as it passes through the respiratory apparatus; however, food undergoes many complex chemical changes during digestion and excretion. As a result, there are two general ways that food can cause cancer: foods may be carcinogenic when we consume them; or initially harmless foods may be converted to carcinogens by our digestive process.
Since we are using tobacco as an introduction to meat-produced cancers, it’s worth pointing out a good reference article from Cancer Research UK. It has excellent graphics that illustrate that, although we should rightly worry about digestive tract cancer, it is far less prevalent than, say, lung cancer: they calculate 8,800 cases per year in the UK of meat-caused cancer, versus 64,500 cases of cancer caused by smoking.
Bacon Cancer: Evil Spirits in the Diet
With that introduction, we can take a short cut through the forest of conflicting esoteric studies and summarize the bad actors, our best guess as to the perpetrators of digestive cancers. There are four:
– Meat processing products. Meats are processed to preserve them and to enhance their flavor. However, the production of processed meat can create chemicals known to cause cancer, including nitrosamines and polycyclic aromatic hydrocarbons (PAH).
– Meat cooking products. Meats are cooked to improve taste and digestibility, and to eliminate harmful microorganisms. However, the process of cooking meat also generates carcinogens, including heterocyclic amines (HCA) and PAH, especially at higher temperatures and longer cooking times.
– Meat processing additives. Meats are frequently cured with the addition of nitrites and nitrates. These are converted to carcinogenic nitrosamines both during cooking and during digestion.
– Intrinsic chemicals in meat. Red meat, especially beef, contains a large amount of heme. Heme is an iron-containing component of hemoglobin that enables the blood to carry oxygen. The iron in heme can promote cancer by enhancing the production of free radicals, by enabling the proliferation of tumor cells and by forming nitrosamines in the colon. Note that heme is intrinsic to meat, especially red meat: if you eat red meat, or in fact any kind of meat, you will consume heme.
This gives you an overview of the bad stuff, the substances in meat that lead to bacon cancer and other meat-caused cancers. Next week’s installment of this blog will discuss what we can do about it, under the heading of Meat Cancer Prevention.