As someone who is interested in food you may have noticed a bit of a hoo ha going on recently in the media regarding meat, at least in the UK. While no ‘expert’ is saying eat as much meat as you like, or that no one should eat meat, there seems to be a bit of misunderstanding of some of the issues as reported in the press and what I am reading online. This wholly biased and only vaguely scientific post is my beef about the reporting of beef. It is my opinion only and shouldn’t be used as the basis of making any decisions about whether or not to eat meat.
This misunderstanding has been going on for quite awhile. I was at the World Cancer Research Fund “Nutrition, Physical Activity and Cancer Prevention: Current Challenges, New Horizons” conference in 2007 (snappy title, I know). Global experts looked at how diet, physical activity and weight management affect cancer risk. All very interesting, of course. No, really. But the conference made the headlines with their challenging findings on meat. Basically, we in the developed countries need to cut down on our meat eating. It was fascinating to see how newspapers reported on this. The immensely popular tabloid paper The Sun, had as its main headline “Save Our Bacon: Butty Battle”. As if bacon and sausages were suddenly going to be swept from the supermarket shelves and onto a giant pyre (ironically causing more cancer-causing compounds).
Alarmist headlines notwithstanding, the media often misrepresent scientific data. They don’t have the space, the time or the expertise to fully cover complex and detailed study findings, nor compare and contrast with other studies and sources. And we the public want our information sanitised and in bite-sized portions. I am not an expert, and this humble recipe-driven blog is perhaps not the place for a discursive essay on the merits and demerits of meat but I feel very strongly that some of the issues – as I see them – are not being addressed, or at least, not in one article, so here goes.
Before I put in my two cents’ worth on pros and cons of meat it is perhaps useful to touch on meat’s social anthropological significance – why we love meat so much. Although up for debate, it is generally held as true that humans evolved as omnivores, meaning that we eat a diet that includes foods of both plant and animal origin. Our teeth, digestive tract and the way we metabolise food for energy points to the importance of a mixed diet for optimal health. Our digestive tract, gut flora and teeth are particularly adaptable to any diet: there are tribes that eat very few plants and, more commonly, there are groups who consume no animal products whatsoever. Whether they are all healthy is debatable. We certainly can survive very well without animal products but it is recognized that vegans (who have no animal products whatsoever) have to be very clever with food combinations to make sure they get adequate useable protein and vitamin B12. The point here is that although people may choose to be vegan or vegetarian, we can digest and use most animals and edible plants.
Anyway, because many people enjoy the taste of meat and because meat-eating is seen globally as a sign of relative affluence, availability and consumption of meat – and red meat in particular – tends to increase as relative income rises. Even in societies where meat is scarce or unaffordable, meat is often a part of feast rituals and celebrations. In affluent societies, non-meat eaters do so mainly for religious or ethical reasons, although more recently health considerations are part of the decision matrix. Compared with the early part of the last century, nutritional deficiencies arising from poverty are a dwindling public health concern, at least in the West. The current health agenda in Western societies and in the rapidly developing East is increasingly focused on ‘over-nutrition’ – basically too much of a good thing. Alongside numerous other so-called lifestyle factors, an overabundance of meat is seen as causing a rise in obesity, diabetes, cardiovascular disease and some cancers. I will have a brief look at colorectal cancer – cancers of the lower digestive tract and rectum, which is at the centre of the present debate about meat.
Colorectal cancer is the third most commonly diagnosed cancer, after breast and lung. It is the second leading cause of death from cancer in the US. In the UK it causes more deaths than breast and cervical cancer combined. Despite the limitations of studying diet and disease, credible studies are increasingly pointing the finger at our collective love of burgers, bacon and sausages as a risk factor for developing colorectal cancer. A 2009 study analyzing cancer statistics in all five continents found that colorectal cancer incidence rates for both males and females increased in 27 of 51 countries worldwide between 1983 and 2002, and indentified “increasing Westernization as being a likely culprit.” It noted that “many of the established and suspected modifiable risk factors for colorectal cancer, including obesity, physical inactivity, smoking, heavy alcohol consumption, a diet high in red or processed meats, and inadequate consumption of fruits and vegetables, are also factors associated with economic development or westernization.” Pretty damning, and little reported in the press.
Splashing all over the media in February was the UK government advice for us to all cut back on our meat intake. They based their advice on research from the Scientific Advisory Committee on Nutrition (SACN), which found that people who eat 90g of red and processed meat or more a day are at an increased risk of bowel cancer. The committee advised reducing this to an average of 70g a day by eating smaller portions or consuming red meat less often. The commercial interests of those sitting on this committee make me wary of any of their pronouncements, especially as the evidence in their report seems to describe problems associated with processed meat but lumps red meat in for good measure (pun intended). But, the globally recognized World Cancer Research Fund (WCRF) have, over the years, flagged up high quality research that does make it clear that the more red and processed meat one eats the more we increase our risk of colorectal cancer (which includes the lower part of the intestinal tract as well as the rectum). Since 2007 their advice has been to eat not more than 500 grams of cooked meat a week (about 700 grams before cooking). Consistently much over this amount is associated with increased risk of colorectal cancer. Exercise, alcohol and obesity are other controllable risk factors. The evidence for some other cancers is what they term ‘limited-suggestive’, meaning that although evidence points to a link the studies may be limited by methodology or size. Other cancers that may be influenced by meat include esophageal, lung, pancreatic, endometrial, stomach and prostate.
The reasons for the link between meat eating and colon/bowel cancer are not clear, although this in itself is not clear in the popular media. This is due partly to the difficult nature of studying the relationship between lifestyle behaviours and incidence of disease. Numerous mechanisms have been proposed and it may be interplay between several known and unknown factors. Fat and saturated fat has been cited as a factor. Possibly, but changed animal husbandry has lowered the fat and saturated fat content in beef cattle. It may take time to see if bowel cancer rates decline in response to this change but dietary fat and cancer generally has been shown to be less of a factor than body weight and abdominal fatness. Another possible related issue is the unnatural diets of most commercially-raised beef cattle, despite what our recent brush with BSE has taught us. We eat what the animals we eat eats, and all that. I will try and read up on that one and report back.
Of more potential interest is the processing of meat, and how we cook meat. The combination of these two factors looks on the face of it quite convincing as a risk factor for colorectal cancer. First of all, chemicals known as heterocyclic amines (HCAs)and polycyclic aromatic hydrocarbons (PAHs) are formed when meat – all meat, not just red – is cooked. These compounds are known to cause DNA changes that increase our risk of cancer. Meat type, cooking method and ‘doneness’ affect the amount of these chemicals that are formed, but the higher the cooking temperature the greater the number of HCAs and PAHs. These compounds are formed in different ways with PAH development being more associated with charred and well-cooked meats while HCAs are associated with any type of cooking and any type of animal protein. Both compounds are damaging only after being activated by certain gut enzymes, which differ among us. This personal variability may account for differences in risk associated with HCAs and PAHs. This association isn’t terribly clear because these chemicals are formed in all cooked meat, including poultry, fish, pork and game. It does vary by meat, but enough to account for a lack of association between these other meats and colorectal cancer? It’s hard to say.
A better bet in the blame game is processed meats, full stop. Few large studies contradict the relationship between processed meat and colorectal cancer. There are a number of mechanisms proposed for cancer development in this area of the body: interaction between self-produced nitrates and ingested nitrates (very convincing), high levels of salt and nitrite (a biologically nasty combination), and iron-containing haem which in high levels can promote damaging free radical production. On the latter, all red meat has haem iron, it’s what makes meat red, but it’s negative effects may possibly be enhanced when combined with additive compounds.
Drawing associations between dietary factors and cancer is fraught with difficulty. The time between cancer initiation, development and progression can be considerable, making it impossible to study the immediate effects of certain foods on the risk of cancer. It is also hard to account for changes in dietary patterns and behaviours over time: think about how your own diet has changed from childhood until now. Additionally, we consume such a variety of foods and drinks, and prepare and consume them in such varying ways that it is difficult to assign estimated risks – or benefits – to certain foods. The interplay between this and other lifestyle factors such as level of physical activity or drinking habits, as well as factoring in the effects of the wider environment and our genetic inheritance, makes it incredibly challenging to offer broad public health advice on food and risk. With this in mind, findings of associations between foods and cancer always have to be considered with caution as it is impossible to account for all possible factors influencing the risk of disease.
I guess what I am trying to say in a massively round about way is that the relationships between what we eat and drink is rarely cut and dried. We are too variable as individuals, in not only our behaviours and exposures but also our genetic makeup, to be so sure of what may or may not protect us from cancer, and for that matter, other diseases as well. Although statistics are very important, they aren’t the entire picture. If what you hear on the TV or read in the newspapers concerns you, make it your business to get the whole story; read around and see how what you read and hear applies to you and how you live your life.
There is a huge body of evidence that indicates that a plant-based diet is a cancer-preventing diet. If you focus on the plants it’s perhaps not as necessary to get worried about the meat. When people eat a more plant-centred diet, using vegetables, pulses, whole grains and the like to form the basis of daily meals, they often find that they find they naturally eat less meat anyway. As for my own take on meat, I have read plenty that convinces me that although meat can can be a part of a balanced and healthy diet, my preference is for minimal red meat and more fish and plant-based proteins. Combined with a fairly high intake of vegetables and fruits, as well as modest amounts of wholegrains and some treats like wine and homemade cakes, my way of eating suits me perfectly. My diet is far from perfect (how boring would that be) but by combining a bit of knowledge with listening to my body I have found what works for me. You find what works for you.