Processed meat and cancer. What does the scientific classification actually say?
The short answer is that it is not directly comparable. The comparison oversimplifies the scientific evidence and can be misleading. Understanding what is actually being compared is key to avoid unnecessary alarm and to make informed decisions about our diet.
In 2015, an international group of experts reviewed hundreds of studies on diet and cancer. Their conclusion was clear: regular consumption of processed meat may increase the risk of colorectal cancer.
This statement is based on solid scientific evidence. The issue, however, lies not with the data itself, but with how it was interpreted. When it was announced that processed meat had been placed in the same classification group as tobacco, many assumed this meant the risks were equivalent. And they are not.
The difference between “can cause cancer” and “carries a risk”
In epidemiology, there are two key concepts:
-
Danger: indicates whether something has the potential to cause cancer.
-
Risk: indicates the actual likelihood of it happening and its impact on the population.
When processed meat is placed on the same category as tobacco, this refers to the level of scientific evidence for a cause-effect relationship, not to the level of risk.
The same strength of scientific evidence does not mean the health risks are equivalent. Smoking remains far more harmful to public health than the consumption of cured meats.
How much does eating cured meat increase cancer risk?
This is the question that really matters. Consuming 50 grams of processed meat per day, roughly equivalent to two or three slices of ham or a single sausage, has been associated with an 18% increase in the relative risk of colorectal cancer.
What does this actually mean?
If, in a given population, 5 out of every 100 people develop colorectal cancer over their lifetime (the absolute risk), eating processed meat would increase this figure to approximately 6 out of 100 people (reflecting the 18% relative risk increase).
The risk rises, but it does not increase exponentially. The difference becomes even clearer when looking at global mortality figures:
-
Around 34,000 deaths per year worldwide are associated with diets high in processed meat.
-
About 1,000,000 cancer deaths per year are attributed to tobacco use.
-
Approximately 600,000 deaths per year are associated with alcohol consumption.
This quantitative difference explains why it is inaccurate to claim that cured meats are "as carcinogenic as tobacco".
What exactly is considered processed meat?
When we talk about processed meat, we are not only referring solely to industrially manufactured products. The term includes any meat that has undergone any of the following processing methods:
-
Salting
-
Curing
-
Smoking
-
Fermentation
-
Canning
Examples of foods in this category include:
-
Ham
-
Deli meats or sliced luncheon meats
-
Sausages and frankfurters
-
Bacon
-
Canned meat
-
Dried meat
These processes help preserve meat and prevent the growth of harmful microorganisms. However, adding nitrites and nitrates during processing, combined with cooking at high temperatures, can lead to the formation of compounds such as nitrosamines, which have been linked to cancer.
It is also important to distinguish processed meat from fresh red meat, which falls into a different category and has a lower level of evidence. How much cured meat can you eat without risk?
There is no absolute “safe threshold” at which risk drops to zero. In public health, risk tends to operate along a spectrum: the greater the quantity and frequency of consumption, the higher the probability of an effect.
Many processed meats now contain antioxidants, such as vitamin C, to slow down the formation of compounds like nitrosamines. Nevertheless, the recommendation to moderate consumption remains in place as a precaution.
Dietary guidelines recommend limiting the consumption of processed meats and prioritising a Mediterranean diet.
In this model, red and cured meats are eaten only occasionally. Such a diet is associated not only with a lower risk of colorectal cancer, but also with reduced rates of cardiovascular disease, type 2 diabetes and a greater life expectancy.
That said, the evidence also indicates that the way these foods are prepared and what they are served with, can influence the formation of harmful compounds. Therefore, it is recommended to prioritise cooking methods such as steaming or baking at moderate temperatures, while grilling, pan frying or cooking over a high heat should be limited.
Moreover, pairing the consumption of processed meats with fibre-rich foods, such as pulses, vegetables or fruit, reduces the time that potentially carcinogenic substances are in contact with the intestine.
The antioxidants, present in many plant-based foods, may help counteract some of the harmful effects of nitrosamines. If you do eat processed meat, it should always be as part of a meal rich in vegetables. There is a big difference between a bacon sandwich on its own and peas sautéed with bacon.
Why does this debate keep coming back?
Although the scientific classification was published years ago, the debate often resurfaces whenever new dietary guidelines are discussed or when the role of animal protein in health is questioned.
Simplified headlines grab more attention than nuanced explanations. But the reality is more complex: risk is influenced by the overall diet, the frequency of consumption, and general lifestyle factors.
Currently, there is broad consensus within the scientific community that a balanced diet, rich in plant-based foods, is associated with better long-term health outcomes.
INFORMATION DOCUMENTED BY:
Dr Joan Trabal, Endocrinology and Nutrition Department, Hospital Clínic Barcelona.
