In July of last year, the International Agency for Research on Cancer (IARC), a branch of the World Health Organization (WHO), made a decision about a common ingredient in sugar-free products worldwide: it included the artificial sweetener aspartame on the list of “possibly carcinogenic” items. The category, officially called 2B, refers to items that evidence suggests a relationship with tumors, but in a limited way in both animal and human studies. This decision may come as a surprise, but IARC’s classification also includes a series of other common foods in our daily lives, such as red and processed meats.
Is aspartame carcinogenic?
But is aspartame really carcinogenic? What other items can increase the risk of cancer? And what are the recommended safe intake limits? Regarding aspartame, the WHO authority points out that the few studies found a possible association with hepatocellular carcinoma, a type of liver tumor.
However, the Joint FAO/WHO Expert Committee on Food Additives decided that these findings were not sufficient to change the established safe daily consumption limit of 40 mg per kg of body weight. Nevertheless, experts suggest that there are reasons to reduce the substance, as it has been shown to be not as harmless as previously thought when it was discovered in the 1960s. For example, the National Cancer Institute (Inca) published a technical note after the WHO decision, advocating to “avoid the consumption of any type of artificial sweetener”: “it is imperative to carefully evaluate the use of this substance.”
Most studies are done in animal models because we cannot directly test the effects of consumption in humans. The studies we have (with humans) are observational, but they did show an association indeed. We know that the animal studies used very high doses, but since we cannot replicate this in humans, it is difficult to establish the exact amount that would be truly safe. So the best approach is to avoid it, especially if you have other risk factors – recommends Andrea Pereira, a medical nutritionist and member of the Multiprofessional Committee of the Brazilian Society of Clinical Oncology (SBOC).
Red and processed meats
While the discussion about aspartame is ongoing, other items are more consistently related to cancer. In its prevention guidelines, Inca highlights five of them: red meats, processed meats, ultra-processed foods in general, alcohol, and the consumption of very hot beverages.
Red meat, such as beef, pork, lamb, and goat, which are significantly present in the Brazilian population’s diet, can be surprising. The IARC classifies red meat in category 2A, as “probably carcinogenic.” This means that there is more robust evidence, especially among animals, linking this food to colorectal, pancreatic, and prostate tumors. According to Inca, red meat is rich in important nutrients such as vitamins and minerals, but it contains a form of iron called heme, derived from red blood cells and muscle cells, which, in excess, increases the risk of cancer. Therefore, both the Brazilian institute and the International Agency for Research on Cancer recommend limiting consumption to 500g per week, which is equivalent to about three servings.
However, more worryingly, processed or processed meats, linked to colorectal and stomach cancers, are classified in group 1 of the IARC table, as proven carcinogens. Some examples are ham, sausage, bacon, salami, bologna, and turkey breast.
These are some of the foods that are most related to cancer. They generally contain substances called heterocyclic amines and nitrosamines, which are proven carcinogens. They are formed due to high temperatures and the industrialization process of these items. The crust that forms on grilled red meat also contains these compounds. So we need to consider reducing the intake of these products – says nutritional doctor Durval Ribas Filho, president of the Brazilian Association of Nutrology (Abran) and fellow of the Obesity Society FTOS – USA.
In this case, there is no recommended safe limit – consumption should be avoided as much as possible. The same is advised regarding ultra-processed foods in general, those ready-to-eat or heat foods, usually packaged, such as lasagna, snacks, biscuits, fast food, sugary drinks, among others.
Although these items are not specified in the IARC table, as they encompass a wide variety, it is known today that their preparation, which involves a high amount of additives, preservatives, salt, and sugar to increase their durability and palatability, is harmful. One of the ways they can increase the risk of cancer is by being highly likely to cause obesity, explain the specialists.
Alcoholic and very hot beverages
When it comes to beverages, there are warnings in two scenarios: alcoholic and very hot beverages. In relation to alcohol, it is also classified in the highest category 1 by IARC. The substance is proven to be associated with various types of tumors, such as mouth, pharynx, and larynx, esophagus, liver, colorectal, breast, and stomach.
Alcohol has two pathways that can cause cancer. We have the mutagenic pathway, due to the potential to cause mutations in cells that can lead to cancer. But in women, we know that there is also a hormonal pathway involved that can increase this risk – says Andrea Pereira, from SBOC.
There is no safe limit set by the main health authorities. However, experts say there are guidelines that suggest a less harmful amount: up to two doses per day for men and one per day for women. One dose corresponds to approximately 14 g of alcohol, equivalent to a can of beer, a glass of wine, or a shot of spirits.
As for very hot beverages, the WHO agency classifies those with temperatures above 65°C in category 2A, as “probably carcinogenic,” just like red meat. This is due to a link found with an increased risk of esophageal cancer.
Inca points out that the problem is the temperature and recommends that it should be below 60°C at the time of consumption. To achieve this, “turn off the heat when bubbles begin to form at the bottom of the pan or kettle and wait five minutes before placing it in the thermos or consuming the drink,” it says.
Dietary pattern is what matters
In general, nutritionist Annete Marum, a PhD in Nutritional Genomics from the Federal University of São Paulo (Unifesp), emphasizes that it is not a single food that can cause cancer, but rather a dietary pattern that involves excessive intake of these harmful ingredients, as well as the absence of other protective factors.
We often talk about a dietary pattern, a habit of excessive exposure to chemicals, low consumption of vitamins and nutrients, a state of obesity. So health depends on nutrition. Fruits, vegetables, and legumes, for example, have vitamins, minerals, bioactive compounds, polyphenols that protect against oxidative stress, protect the body from inflammatory stress. So low consumption of these foods also favors the onset of the disease – she explains.
Ribas Filho points out that the lack of education about the properties of each food is a problem in the country: – A good part of the population does not have specific knowledge about what a functional food is, such as fruits and vegetables, and a carcinogen, for example. This teaching has to start in schools, with children and teenagers.
According to Pamela Almeida, an oncologist and also a member of the Multiprofessional Committee of SBOC, a measure that could help is clearer communication on labels about the risks:
Foods should clearly indicate their components and even their classifications by the WHO in terms of harm to health. This way, the population could better select foods and start playing their role in preventing cancer and other diseases related to an unhealthy diet.
