Meat, Fish & Dairy Products and Cancer Risk

Following on from the previous blog, which looked at how the methods used in processing and preserving your food can ramp up the nasty possibility that one day your doc will mention the ‘C’ word ¹ , we’ll look today at the cancer risks involved in eating meat, fish and dairy products.

The Continuous Update Project (CUP), which analyses research on what causes cancer and how it can be prevented, operates under the auspices of the WCRF/AICR (World Cancer Research Fund/American Institute for Cancer Research). The following information is taken from their Third Expert Report ² released in 2018.

The major findings of this Report are:

There’s strong evidence that consuming:
- processed meat INCREASES the risk of colorectal cancer (covered already ¹ )
- red meat INCREASES the risk of colorectal cancer
- Cantonese-style salted fish INCREASES the risk of nasopharyngeal cancer (covered already ¹ )
- dairy products DECREASE the risk of colorectal cancer
There’s limited evidence that consuming:
- fish DECREASES the risk of liver cancer and colorectum cancer
- red meat INCREASES the risk of nasopharyngeal cancer, lung cancer and pancreatic cancer
- processed meat INCREASES the risk of nasopharyngeal cancer, oesophageal cancer, lung cancer, stomach cancer and pancreatic cancer
- foods containing haem iron INCREASE the risk of colorectal cancer
- grilled or barbecued meat or fish INCREASE the risk of stomach cancer
- dairy products DECREASE the risk of breast (premenopausal) cancer
- dairy products INCREASE the risk of prostate cancer
- diets high in calcium DECREASE breast (premenopausal & postmenopausal) cancer
- diets high in calcium INCREASE prostate cancer

The following is a chart which shows the above information in a more graphic format.

Full details are available at as a downloadable PDF file ³ .

As mentioned above, the salted fish and any processed meats should simply be avoided at all costs – if, that is, you want to do the best you can to avoid cancer risk.

Mechanisms involved in cancer risk

Red meat and cancer

A number of mechanisms are involved, including:

cooking meats at high temperatures results in the formation of heterocyclic amines ⁴ and polycyclic aromatic hydrocarbons ⁵ , both of which have been linked to colorectal cancer
haem iron, which is present at high levels in red meat, has been shown ⁶ to promote colorectal tumorigenesis (the process involved in the production of a new tumour or tumours) by stimulating the endogenous formation of carcinogenic N-nitroso compounds ⁷

The Report adds: “Polycyclic aromatic hydrocarbons, which are formed when organic substances like meat are burnt incompletely, may also have carcinogenic potential. Grilling (broiling) and barbecuing (charbroiling) meat, fish, or other foods with intense heat over a direct flame results in fat dropping on the hot fire, causing flames; these flames contain polycyclic aromatic hydrocarbons that stick to the surface of food.”

Processed meat and cancer

A number of mechanisms are involved (covered in the previous blog ¹ ), including:

similar to red meat, processed meat is rich in fat ⁸ , protein ⁹ and haem iron ⁶ , which can promote tumorigenesis (the process involved in the production of a new tumour or tumours)
processed meats are often cooked at high temperatures, which can lead to increased exposure to heterocyclic amines ⁴ and polycyclic aromatic hydrocarbons ⁵
processed meat is invariably higher in fat content than red meat, which may promote carcinogenesis through synthesis of secondary bile acids ¹⁰ ; however, the Report suggests that human data only offers weak support of this hypothesis at the moment, with more research being needed
processed meat is also a source of exogenously derived N-nitroso compounds ¹¹ ¹² , which may have carcinogenic potential.

Dairy and cancer

A number of mechanisms are involved, including:

their high calcium content (see below in Joe’s Comments for a discussion of this)
the lactic acid-producing bacteria in dairy may also be protective ¹³ ¹⁴
casein [the protein in dairy] and lactose [a sugar in dairy] in milk may increase calcium bioavailability
other nutrients or bioactive constituents in dairy products, such as lactoferrin ¹⁵ , vitamin D (from fortified dairy products) or the short-chain fatty acid butyrate [see blog ¹⁶ for more on this amazing acid] may also impart some protective functions

The CUP Panel stated that the above require much better research, and that: “…the evidence was generally consistent for dairy products, milk, cheese and dietary calcium, and showed a decreased risk of colorectal cancer with higher consumption.”

Joe’s Comments

The findings on red meat are interesting in relation to cancer risk – basically, there is zero evidence that eating it will help to prevent cancer – indeed, quite the reverse appears to be the case. So why bother with it?

Equally revealing is the evidence about fish (not the Cantonese salted stuff, but just general fish). It may well be that there is some evidence that eating it may protect against two forms of cancer (liver and colorectal), but this doesn’t take into account the other health problems associated with eating fish, covered in an earlier blog ¹⁷ . And, in any event, this Report does not look at whether or not you would stand a better chance of avoiding liver and colorectal cancer by dumping fish altogether and eating a whole food plant-based diet instead. This is always the issue with this type of research – the research team always needs to limit their field of enquiry (reductionism vs wholism ¹⁸ in order to get funding and draw ‘neat’ conclusions.

Additionally, did you notice the part about foods high in calcium? If you look at the full report ³ , you will see that they are mainly talking about high calcium sources being derived from dairy products – “In countries with high intakes of dairy products, these products are the main source of calcium.” What the Report does not mention (because of milk industry pressure?!) is that dairy consumption is associated with increased rates of osteoporosis/hip fractures and that dairy appears to leach calcium from bones rather than build up bones ¹⁹ ²⁰ ²¹ ²² ²³ ²⁴ ²⁵ .

Yes, there are many other studies that suggest that the calcium in dairy is great for your bones, but the very fact that there are good research studies that suggest otherwise makes dairy one more ‘smoking gun’ ²⁶ that does no harm to avoid – especially since, as the report itself states ²⁷ ²⁸ , you can get all your calcium from plants ²⁹ ³⁰ . In any event, avoid calcium supplements ³¹ ³² .

And this isn’t the only issue to worry about when it comes to dairy products. As the Report authors themselves state:

“The Panel did not base a recommendation on the strong evidence that the consumption of dairy products decreases the risk of colorectal cancer as there is some other evidence that is suggestive of an increased risk of prostate cancer, although that evidence fell below the general threshold required for making a recommendation. For more information on when the evidence is divergent between cancer sites.”

Once more, there always appears to be that ‘smoking gun’ ²⁶ when it comes to animal foods that is simply not an issue when dealing with plant foods.

In the next blog, we will take a quick look at what the Report had to say about the relationship between cancer risk and wholegrains, vegetables and fruit. Want to guess whether they’ll be more factors that decrease or increase cancer risk?

References

Food Processing & Preserving Causes Cancer

Following on from the previous blog which looked at how even the smallest consumption of alcohol is not safe, in terms of its ability to increase your risk of certain cancers, this blog looks at how the methods used in processing and preserving your food can also ramp up the nasty possibility that one day your doc will mention the ‘C’ word.

The Continuous Update Project (CUP), which analyses research on what causes cancer and how it can be prevented, operates under the auspices of the WCRF/AICR (World Cancer Research Fund/American Institute for Cancer Research). The following information is taken from their Third Expert Report ¹ released in 2018.

The major findings of this Report are:

there’s strong evidence that consuming:
- processed meat INCREASES the risk of colorectal cancer
- Cantonese-style salted fish INCREASES the risk of nasopharyngeal cancer
- foods preserved by salting INCREASES the risk of stomach cancer
there’s limited evidence that consuming:
- preserved non-starchy vegetables INCREASES the risk of nasopharyngeal cancer
- processed meat INCREASES the risk of:
  - nasopharyngeal cancer
  - oesophageal cancer
  - lung cancer
  - stomach cancer (non-cardia ² )
  - pancreatic cancer

This information can be seen in the following chart.

Processing & Salting

The processing and preserving methods affect the chemical composition of foods as well as their nutritional value and carcinogenic potential.

Processed meats, as defined by the Report, are:

“meats (usually red meats) that have been preserved by salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation.

Examples of processed meat include ham, salami, bacon, pastrami and some sausages. These include sausages, bratwursts, chorizo, frankfurters and ‘hot dogs’ to which nitrites or nitrates or other preservatives are added.”

Around the world, raw fish is widely preserved by salting and, depending on the precise conditions, salt-preserved fish may also undergo fermentation.

Cantonese-style salted fish uses less salt and a higher degree of fermentation than other methods of fish preservation. Some diets around the world still include significant quantities of salt-preserved foods, including salted meat, fish, vegetables and sometimes even fruit.

The World Health Organisation (WHO) recommends a daily maximum salt consumption of less than 5 grams (equal to less than 2 grams of sodium). ³ The Report advises that nobody should consume Cantonese-style salted fish.

Additionally, they say it’s best not to consume any foods that have been preserved by salting.

The possible mechanisms involved

Processed meat and colorectal cancer

It’s likely that a number of mechanisms are involved, including the following:

similar to red meat, processed meat is rich in fat ⁴ , protein ⁵ and haem iron ⁶ , which can promote tumorigenesis (the process involved in the production of a new tumour or tumours)
processed meats are often cooked at high temperatures, which can lead to increased exposure to heterocyclic amines ⁷ and polycyclic aromatic hydrocarbons ⁸
processed meat is invariably higher in fat content than red meat, which may promote carcinogenesis through synthesis of secondary bile acids ⁹ ; however, the Report suggests that human data only offers weak support of this hypothesis at the moment, with more research being needed
processed meat is also a source of exogenously derived N-nitroso compounds ¹⁰ ¹¹ , which may have carcinogenic potential.

Cantonese-style salted fish and nasopharyngeal cancer

Cantonese-style salted fish contains nitrosamines and nitrosamine precursors ¹² . Some samples of Cantonese-style salted fish have been shown to have high levels of a nitrosamine called N-nitrosodimethylamine ¹³ and, in experimental models with animals, this has been found to found to induce cancer development.

Salt preservation and stomach cancer

There is good evidence that salt preservation can cause stomach cancer ¹⁴ . The following are suggested mechanisms:

high salt levels can alter the viscosity of the mucous protecting the stomach and, hence, enhance the formation of N-nitroso compounds
high salt intake may stimulate the colonisation of Helicobacter pylori (also known as H pylori, previously known as Campylobacter pylori, which is a gram-negative, microaerophilic bacterium usually found in the stomach) which is the strongest known risk factor for stomach cancer ¹⁵ ¹⁶
high salt levels have been shown to be responsible for the primary cellular damage which results in the promotion of stomach cancer development ¹⁷ ¹⁸

There’s more information available ¹⁹ on the process by which cancer develops. You may also be interested in a blog I wrote about the fascinating subject, intimately related to cancer development, of angiogenesis and the work of Dr William Li ²⁰ .

Final Recommendations of the Report

If you want to do all you can to avoid cancer, the Report recommends that: “[f]or people who eat meat, the recommendation is to eat little, if any, processed meat.”

Joe’s Comments

What stands out to me on the above chart is that there is nothing entered in the green column (i.e. evidence that these foods in any way decrease the risk of cancer. Isn’t this enough for any sensible person to conclude that such processed and salt-preserved foods should simply be removed from their diet – completely? Of course, we’re not all sensible people and even the sensible ones amongst us are not sensible all the time.

Of course sausage and bacon, salty and smoked fish taste wonderful and are so tempting – but I understand that injecting heroin is a wonderful (though transient) experience. Rushing out to buy some syringes?

Next blog

In the next blog we’ll take a quick look at the WCRF/AICR findings on how meat, fish and dairy consumption affects the risk of developing cancer.