We often hear people saying 'oh, this food is carcinogenic' and 'eating this causes cancer', but many of us don't really know why this is.
How does a food become carcinogenic? Does eating them definitely cause cancer? Should we avoid these things altogether?
To get the answers to these important questions, The Huffington Post Australia talked to Cancer Council NSW spokesperson and nutrition program manager, Clare Hughes.
What does it mean for a food to be carcinogenic?
"Put simply, a carcinogen is something that causes cancer," Hughes told HuffPost Australia. "It can be substances like tobacco and other chemicals, or it can be something you're exposed to like UV radiation or particular viruses."
For a food to be carcinogenic, there must be strong evidence linking consumption of the product to an increased incidence of specific cancers, as well as evidence about how that food can cause cancer to develop.
"The carcinogenic foods with the greatest evidence are alcohol, processed meat and red meat," Hughes said.
However, it's important to emphasise that carcinogenic foods means there's a link to cancer, not how much cancer a food causes.
"It's important to understand that when a food is classified as a carcinogen, this is an indication of how strong the evidence is of the link between consumption and cancer," Hughes explained. "It is not an indication of how much cancer that food causes or how much of that food would give you cancer."
Here are some everyday foods and drinks that are labeled as carcinogenic:
- Processed meats such as bacon, sausages, hot dogs, pepperoni, prosciutto, beef jerky and salami (any meat that has been preserved by curing, salting or smoking, or by adding chemical preservatives)
- Alcoholic beverages
- Salted fish (Chinese style)
- Burned or heavily barbecued foods
- Red meat including, beef, veal, pork, lamb, mutton, horse and goat
- Hot beverages above 65°C
- Polluted air and water
Alcohol
"There are a whole range of ways that different carcinogens cause cancer to develop," Hughes told HuffPost Australia. "Even the same carcinogen, such as alcohol, causes cancer in different ways in different parts of the body."
Alcohol is classified as a 'Group 1 carcinogen' which means that, like processed meat, the evidence that alcohol can be linked to cancer is extremely strong, Hughes explained -- particularly cancer of the mouth, throat, esophagus, breast, liver, stomach and bowel.
"It's estimated that around 3,200 cancer cases in Australia are attributed to alcohol consumption each year."
The reason why alcohol is linked to cancer is because alcohol can damage the lining of the mouth and throat, causing cancer in these parts of the body.
"Alcohol can also impact the levels of hormones that are linked to breast cancer," Hughes said.
Red and processed meats
The World Health Organisation has classified processed meats including ham, salami, sausages and hot dogs as a 'Group 1 carcinogen', which means that there's strong evidence that processed meats is linked to cancer, Hughes said.
"Red meat, such as beef, lamb and pork, has been classified as a Group 2A carcinogen which means it's a 'probable' cause of cancer," Hughes added.
The reason why red meat and processed meats are carcinogenic is due to the chemicals they contain.
"Current research indicates that there are certain chemicals in red and processed meats -- both added and naturally occurring -- that cause these foods to be carcinogenic," Hughes explained.
In terms of cancer risk there is no reason to cut meat completely from your diet but Cancer Council does recommend eating only moderate amounts, which is approximately 65-100g of cooked red meat 3-4 times a week.
"For example, when a chemical in red meat called haem is broken down in the gut, N-nitroso chemicals are formed and these have been found to damage the cells that line the bowel, which can lead to bowel cancer.
"These same chemicals also form when processed meat is digested. The nitrite preservatives used to preserve processed meat also produce these N-nitroso chemicals and can lead to bowel cancer."
However, it's not as though you only need to eat one big serving of bacon to get cancer.
"The risk of developing cancer based on ingesting foods classified as carcinogenic also depends on other factors including how the individual is exposed to the product, how much they eat and for how long they have been eating it," Hughes said.
How much can we eat of these before the risk potentially becomes great?
This is where things get a bit tricky. While carcinogens like cigarettes should be avoided altogether, foods like red meat have some benefits, too.
"Lean red meat can be an important source of iron, zinc, vitamin B12 and protein," Hughes told HuffPost Australia.
"In terms of cancer risk there is no reason to cut meat completely from your diet but Cancer Council does recommend eating only moderate amounts, which is approximately 65-100g of cooked red meat 3-4 times a week.
"You could also try adding egg, beans, lentils, fish or chicken to your meals for a protein hit."
When it comes to processed meat, Hughes recommends saving these as a 'sometimes' food, or removing them completely.
"Keep processed meat to an absolute minimum or, better yet, cut it out completely," Hughes said. "Swap the prosciutto or ham pizza topping by adding chicken, mushrooms or capsicum instead or try marinated chicken, grilled fish or lentil patties.
As for alcohol, while zero intake is ideal (but unachievable), limiting alcohol consumption to less than two standard drinks a day is a good idea.
"Any level of alcohol increases your cancer risk," Hughes said. "The more you drink the greater your risk of developing cancer. And if you drink alcohol and smoke your risk is even higher, as the effect of smoking and alcohol on the body is more significant than the individual behaviours alone.
"To reduce cancer risk, Cancer Council recommends people limit alcohol consumption. People who choose to drink should drink only within the National Health and Medical Research Council Alcohol Guidelines, consuming no more than two standard drinks each day."