The warning from the WHO about cancer risks from processed meats on Oct 26, 2015 was not really a surprise. The fact that cancers can arise from such food has been known for quite a long time and now, finally, processed meats has been placed in the same category as known human carcinogens such as plutonium, asbestos, tobacco and alcohol.

The justification for the ban is somewhat less obvious, apart from the usual “it’s bad for you because some scientists say so after some studies”. So for those who are curious, following are some of the pertinent reasons why the warning was issued.

Don’t we all process meat?

For a start, it would not hurt to understand the term “processed meats”. Frankly, anything done to meat in a kitchen can be considered as “processing” – this includes marinating, frying, boiling, roasting, whatever. It is actually practically impossible to eat meat without some form of processing. But this is not the form of processing meant by the WHO. What they meant by “processed meats” is meat that has been modified chemically, or via curing or smoking processes, to extend its shelf life or to change its taste. Mincing meat through a meat grinder does not result in “processed meat”, unless other ingredients are added. And similarly, cooking raw meat in the kitchen also does not result in “processed meat” in the WHO context.

So ultimately, the problem is mainly to do with the inclusion of chemical compounds into good raw meat – some compounds are added deliberately or created by curing processes such as smoking and perhaps the slow Maillard reaction (eg. for dry-cured hams). There is an additional, lesser warning about red meats too but we will deal with that another time.

Our stomachs are nitrosamine factories

The chemical compounds are included usually as a means to prolong the shelf life or to enhance the taste of the meat. The main culprit appears to be nitrites, which under certain conditions, including the acidic environment in the human stomach, turns into nitrosamines – and most nitrosamines have been identified as significantly carcinogenic. How nitrites turn into nitrosamines is relatively straightforward – in acidic conditions, nitrites form nitrous acid which is highly reactive with amines which are base compounds which arise from the breakdown of proteins. So, in simple terms, nitrous acid plus amine becomes a nitrosamine – therefore the stomach itself creates nitrosamines during digestion. Note that amino acids in meat are amines – they form part of the structure of meat proteins so processed meat will always create nitrosamines in the gut. As an aside, some well-known amines are neurotransmitters such as epinephrine, norepinephrine, dopamine, serotonin and histamine – so they are part of a complex chemical family essential to life itself. However, nitrosamines are not amines – nitrosamines are rather more dangerous compounds and it should be noted that they can also be formed when nitrites are heated with amines during cooking.

In the late 1950s, research had established that 90% of known nitrosamines causes cancers in laboratory animals – and this was confirmed in the 1970s when farm animals in Norway were found to have abnormal rates of liver cancer (due to their feed which contained fish meal preserved with sodium nitrite which had reacted with the amino acids in fish protein to form a nitrosamine called dimethylnitrosamine). Interestingly, nitrosamines are also used in the production of latex products such as balloons and condoms, but unless one is particularly prone to eating balloons, there isn’t too much risk from using rubber products – in particular, a study has shown that condoms are really safe, unless they are somehow ingested (for whatever unknown reasons).


Some researchers have concluded that polycyclic aromatic hydrocarbons (PAHs) present in meats are also involved in cancers. The PAHs would have been introduced into meats via processes that involve smoking with wood and other aromatic compounds, and particularly if food has been cooked over sooty wood or raw fires. By the same token, it is also never ever a good idea to grill or barbecue meat or food over an open kerosene or hydrocarbon-based flame.

Processed meats, including hotdogs and bacon, cook in a frying pan in Miami, Florida. Photo: AFP

Processed meats, including hotdogs and bacon, cook in a frying pan in Miami, Florida. Photo: AFP

Nitrites are not going away

So what are nitrites doing in our meats? One obvious reason is that they prolong the shelf life of meat – in particular, nitrites are very effective against anaerobic bacteria that can produce clostridium botulinum toxin (botulism). Although the United States had considered banning the use of nitrites in meat since the 1970s, the food industry has always fought and won against such actions. Without the use of preservatives such as nitrites, the cost to the processed meat industry would be enormous. However, the US Department of Agriculture did manage to introduce a measure which compelled the food industry to include sodium ascorbate (or sodium erythorbate) in the production of bacon – this was an interesting development for it seems that sodium ascorbate (a derivative of Vitamin C) does seem to inhibit the formation of some nitrosamines (mainly one called nitrosopyrrolidine) in bacon when it is fried.

One interesting but cosmetic aspect of using nitrites in meat is that the compounds help keep meat looking pink and fresh – a quite desirable side effect for meat producers. By chance, I recently had a chance to try in Barcelona, Spain some slices of a jamón Ibérico Bellotta (dried cured ham) which contained no nitrites – and the first thing that hit me was that it was not so attractive visually (being rather brownish in colour). Taste wise, the untreated jamón was also a little less succulent than the usual jamón with nitrites, but it was still very delicious – and expensive.

The stats

In any case, it seems that nitrites (and in some cases, nitrates which breakdown into nitrites) are here to stay in our processed meats. So what is the real danger of ingesting nitrosamines? Several sources have indicated that it is not nearly as dangerous as smoking or sniffing asbestos – and in this they are correct. Statistics from the BBC indicate that around 6% of the UK population will get bowel cancer at some point in life regardless of their diet – and eating 50 grams of bacon daily by the whole population will increase that risk to approximately 7%, an increase of about 18%. Overall, including processed meats with red meat, it is estimated that they cause 21% of all bowel cancers. Note that this 21% refers to incidence of bowel cancer only and not to cancers as a whole. As an occurrence, bowel cancer only happens to 6% of the UK population and not all are fatal – in fact, the survival rate is around 57%.

Lung cancer, by comparison, has a survival rate of only 5% – and is responsible in the UK for 13% of all new cancers annually, over 30% of all cancer deaths. A sobering 86% of all lung cancers are caused by smoking. In hard numbers, some 45,000 people in the UK are diagnosed with lung cancer annually with around 35,000 dying from the disease. Interestingly, non-smokers have only a 4% chance of developing lung cancer so the causative link is much clearer between tobacco and cancer, compared to processed meat and cancer. Put simply, if smoking had never existed, the number of people with lung cancer in the UK will fall from 45,000 to less than 14,000 annually. Maybe you are now wondering why people get cancer at all – this is a valid question which will be explained later in the next sections.

Why I’m still eating processed meats

One important aspect about the WHO recommendation against processed meats should be noted: the statistics on which the recommendation was based comes from general dietary consumption data. It does not take into account the precise consumption patterns of the people who develop bowel cancer. Vegans and pure meat-lovers are both lumped in with the general population data. There’s a higher probability that someone who likes bacon and burgers is likely to eat them in sugary buns with all the trimmings (including artificial cheese slices) – and is also inclined to eat less fruit and vegetables, drink more alcohol (another known carcinogen) while devouring more grilled meats, processed meals and other foods which may have large quantities of other additives, colourings and Advanced Glycation End products (AGEs). All this is likely to have a negative effect on the intestinal flora which is important for maintaining a healthy body. This type of diet is inherently more risky by any definition, perhaps exponentially so if persisted over a long time – and the point is that no guidance was provided by the WHO about the risk levels of cancer against the volumes of consumption of processed meats. On the other hand, I can understand that perhaps it was too impractical to derive such statistics – and technically, on balance, the WHO is plausibly correct to link processed meat with cancer, if only because of the nitrosamines.

However, one would also suggest that a reasonably controlled consumption of such meat would probably not raise the chances of getting cancer significantly. At least, I personally won’t be cutting down on my infrequent consumption of bacon, sausages and ham.

Juicy sausages and succulent smoked meats made the artisanal way. Photo: The Star/Yap Chee Hong

Juicy sausages and succulent smoked meats made the artisanal way. Photo: The Star/Yap Chee Hong

The immutable forces

Some cynics have often said, rather indignantly, that it seems that modern society is caught between two immutable forces – a food industry that wants to make money by selling the most expedient products, seemingly regardless of the consequences, and a medical industry that wants to help combat the effects of our own lousy life choices but at a huge financial cost. Although it is true that doctors cannot make money while you are healthy, I cannot subscribe to such a paranoid view – and it is certainly generally simple to avoid ingesting food which is really unhealthy for your body.

I had originally not intended to write anything about cancers as it is a difficult subject – 3 of my closest friends all died of cancers prematurely and I am also aware of the immensely emotional reactions to this disease by many people. However, there are some points which are worth knowing, even though some are not necessarily very palatable.

An unfortunate predisposition

One point is that humans are more or less genetically predisposed to developing cancer. In Palaeolithic times, humans rarely lived beyond the age of 28 or so, and hence the human body had evolved to hold only limited copies of a tumour antigen gene, known as TP53 – the reason is simply that humans are not designed to live as long as they are doing today. If you’re curious, TP53 is the gene which encodes proteins to bind to DNA and importantly, also regulates gene expression to prevent mutations of the genetic structure of cells.

Cancer happens due to semi-random or wholly random mutations of our internal body cells – semi-random mutations are probably caused by environmental carcinogens – and as such, it would be reasonable to assume that mammals with more cells would simply be more prone to cancer. Hence it was surprising to learn that elephants only have a 5% chance of developing cancers, despite having over 100 times more cells than humans. This compares to the over 30% chance of a human developing cancer over a lifetime.

It turns out that relative to humans, elephants have 20 times more TP53 genes expressed throughout their genetic structure – and as this gene has been known to suppress the onset of tumours, elephants are simply much more immune to developing cancers.

Human cancer rates may also be linked to lower levels of a complex polysaccharide called hyaluronan. This compound comes in the picture due to studies of naked mole rats, which never develop cancer, despite every known carcinogen thrown at or fed to them. It seems that hyaluronan affects the mechanical strength of cell walls as well as also regulating cell growth – and having 5 times as much hyaluronan as humans seem to confer naked mole rats protection against all forms of cancers.

But there’s nothing we can currently do with the information about TP53 and hyaluronan – maybe something may arise in the future as research has already started on them.

Watch for the wrong stuff

So the second thing to consider is that, if we don’t wish to develop cancer, then it is always a good idea to reduce the amount of actual or potential carcinogens that we ingest. This usually just involves reading the labels of the food packaging and eliminating or reducing foods loaded with nitrites, nitrates, added sugars and other unwholesome stuff. Avoid too much fried and takeaway convenience foods too, as you often don’t really know what is in them – and they are also likely to be packed with AGEs. Better still, cook at home more often and try to eliminate eating sugars and burnt foods. And of course, avoid people smoking around you, or breathing polluted air.

Fix it, quickly

The third thing to remember is that it is impossible to avoid eating food which may be unhealthy but too tasty to avoid (or maybe it’s just too inconvenient or impolite to refuse). The best thing then is to also ingest something which can help counter the unhealthy item, like fruits with Vitamin C, or fresh vegetables with a lot of fibre. There is no shortage of lists on the internet of healthy foods to eat so perhaps just follow a list that suits your circumstances best.

These following last two items are purely subjective and therefore definitely not medical advice so please note this.

Hot dogs rest on a a shelf for sale at a grocery store in Centreville, Maryland. Photo: AFP

Hot dogs rest on a a shelf for sale at a grocery store in Centreville, Maryland. Photo: AFP

Don’t feed a cancer

The first item is that if one does start to feel unwell, then a plausible suggestion may be never consent to feed the disease. The metabolism of cancer cells is an anaerobic process and it depends on receiving lots of glucose to feed a new tumour. This is because the mitochondria in cells are damaged so cancer cells need approximately 19 times the amount of glucose to survive compared to a normal cell – this fact is used by PET scans to track tumours. So an idea may be to cut down immediately on all kinds of sugars, to deprive the cancerous cells as much as possible of their food supply. Ignore all the rubbish about alkaline diets and other quack stuff – the main thing is to deprive such abnormal cells of their energy supply and then they would be less likely to metastase and spread.

Resetting the human immune system

The second item is related to a curious fact about the human body – the human immune system can be “reset” and boosted by fasting for between 3 to 5 days. By fasting, it doesn’t mean not eating anything – but it does mean eating less than, say, 200 calories a day and drinking as much mineral water as required. This is quite easily achievable with a diet of some lean meat combined with raw celery, cucumbers and other vegetables. The reasons why this puny diet works are not quite fully understood but it may be that the lowering of white blood cell counts during fasting triggers the immune system to produce new white blood cells. The initial fall of the white blood cells may be due to the body recycling existing cells or re-attuning them to current circumstances. Another factor may be the reduction of certain enzymes and hormones which may help rebalance the body’s internal functions. For example, the hormone IGF-1 is linked to ageing and tumour growth and this is lowered during fasting. Yet another possibility is that the metabolic system may be boosted to burn calories more efficiently across the whole body. Whatever the reasons, a strong healthy immune system is always a good weapon to have against cancer and other diseases.

Another point linked to fasting: Many people have some fixation about staying at a steady weight throughout the year – this is probably based largely on current dietary advice. However, our Palaeolithic ancestors did not have ready supplies of food available all year round and so it was highly probable that their body weights would have fluctuated significantly throughout the year. When they had a good hunting kill, a bountiful crop harvest or a plentiful fruit season, then they would gorge on the food and gain weight. At other times, they were probably verging on starvation and therefore lose weight as a result – and at times of such reduced food supply, the body probably recognised that it needed to beef up its defences against diseases and infections if it was to prolong its survival. So paradoxically, a very limited food supply for a period of time may actually significantly improve the body’s internal defence mechanisms.

Don’t do what I did at home

As mentioned, the above two items about the deprivation of sugar and fasting are only subjective thoughts, and although they are based on current scientific evidence, please understand clearly that they should never be attempted without prior medical consultation. As a little note, I recently tested on myself a four-day diet of 200 calories a day and there have been no negative effects at all – rather the opposite, as a chronic sinusitis condition appears to have gone away for the moment.