heterocyclic amines and polycyclic aromatic hydrocarbons

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.

Tag: heterocyclic amines and polycyclic aromatic hydrocarbons

Food Processing & Preserving Causes Cancer