Can these popular foods cause cancer?

By Naveed Saleh, MD, MS
Published June 22, 2020

Key Takeaways

Care to hazard a guess as to how much food the average American scarfs down in a year? According to 2007-2010 food consumption data collected by the United States Department of Agriculture, the average American eats roughly 1,996 lb of food a year—including 630 lb of dairy, 185 lb of poultry and meat, 197 lb of wheat and grain, and 273 lb of fruit. With all that exposure to food, it’s worth looking at whether any of these food choices could seriously endanger your health (apart from weight gain, of course). 

Obesity is only one aspect of health, and food (which is the fuel of life) is undoubtedly tied to a myriad of diseases—the scariest probably being cancer. So, how do some of our favorite foods increase cancer risk? The answers may be surprising.

Ultra-processed foods

Throughout the world, consumption of ultra-processed foods, such as junk foods and packaged breads, has exploded in recent decades. Manufacturers of these foods employ a variety of dubious practices during creation—including variegating physical, biological, and/or chemical processes—to render these foodstuffs convenient, microbiologically safe, tasty, and affordable. Various surveys—including those conducted in the United States, Canada, and Europe—have shown that between 25% and 50% of the average diet consists of ultra-processed foods.

A variety of food groups can be ultra-processed, with the most common forms being sugary products, drinks, starchy foods/breakfast cereals, and some fruits and vegetables.

Ultra-processed foods are unhealthy for a variety of reasons. First, they harbor higher total fat content, saturated fat content, added sugar and salt, as well as lower fiber and vitamin density. In addition, during their production, new contaminants—specifically carcinogens—may form secondary to heat processing, including acrylamide, heterocyclic amines, and polycyclic aromatic hydrocarbons. Not only that, but the packaging of these foods may also contain materials that are in contact with the food and have carcinogenic endocrine-disrupting properties, such as bisphenol A. Finally, food additives found in ultra-processed foods—such as sodium nitrite in processed meat or titanium oxide (a food whitener)—have demonstrated carcinogenic properties in preclinical studies.

In a high-power, population-based cohort study, researchers found that a 10% increase in the amount of ultra-processed foods consumed correlated with a greater than 10% increase in the risks of overall cancer and breast cancer. 

Sugary drinks

The association between sugary drinks and cardiometabolic disease has been sufficiently sussed out and comes as a surprise to no one. However, the link between sugary drinks and cancer hasn’t been as well researched. 

In a large prospective study published in the BMJ, researchers found that the intake of sugar-sweetened beverages was correlated with an increased risk of overall cancer and breast cancer. Moreover, 100% fruit juices were also linked to overall cancer. The authors suggested that consumption of sugar-sweetened beverages may be a modifiable risk factor to curb cancer risk.

The authors expounded on potential mechanisms underlying an association between cancer and sugary drinks. “Indeed, sugary drinks are convincingly associated with the risk of obesity, which in turn, is recognised as a strong risk factor for many cancers,” they wrote.

They continued: “Apart from the obesity and adiposity pathways, mechanisms underlying a link between sugary drinks and cancer might involve insulin resistance caused by their high glycaemic index or glycaemic load, which have been related to breast cancer, hepatocellular cancer, and diabetes related carcinomas. The chemical compounds in sugary drinks, such as 4-methylimidazole in drinks containing caramel colourings (defined as possibly carcinogenic to humans by the International Agency for Research on Cancer, IARC), pesticides in fruit juices, or artificial sweeteners such as aspartame might play a role in carcinogenesis.”

Baked goods (potassium bromate)

Gluten found in bread binds dough secondary to oxidation with air. Potassium bromate is a powerful oxidizing agent used in commercial baking (when nobody has time to knead bread by hand). It has been in use in the United States since 1914, but is banned in the European Union, Canada, Brazil, and other countries after results from preclinical studies showed that it had carcinogenic potential in rats. For example, one preclinical study showed that rats fed potassium bromate in distilled water had higher rates of renal cell tumors and mesotheliomas of the peritoneum.

When potassium bromate is added to dough that is baked for long enough and at a high-enough temperature, it is converted to potassium bromide, an innocuous substance. But, this transformation doesn’t always occur completely, and some potassium bromate can remain. In the United States, many bakeries no longer use potassium bromate due to concerns over safety, and California law requires that products baked with it be labeled as such.

Cured and processed meats (nitrite)

Nitrites are abundant in cured meats, but are they safe? This compound is used as preservatives to fend against harmful bacteria in processed and cured meats like ham and salami. But, under certain conditions in the human body—dependent on a host of factors like the food and bacteria in your gut as well as the amount of nitrite ingested— nitrites can damage cells and even transform into cancer-causing molecules. 

According to the IARC, there is some evidence supporting the carcinogenicity of nitrites in food, with these compounds tied to stomach cancer:

“Nitrosating agents that arise from nitrite under acidic gastric conditions react readily with nitrosatable compounds, especially secondary amines and amides, to generate N-nitroso compounds. These nitrosating conditions are enhanced following ingestion of additional nitrate, nitrite or nitrosatable compounds. Some of the N-nitroso compounds that could be formed in humans under these conditions are known carcinogens.”

Artificially sweetened foods and drinks (aspartame)

This widely consumed, non-nutritive sweetener has a controversial track record. Although hundreds of studies support aspartame’s safety, countless others do not. High aspartame intake has been shown to induce or exacerbate headaches, and some researchers have linked the artificial sweetener to higher risks of dementia and seizures. But, what about cancer? Studies in murine models have demonstrated mixed results with respect to the carcinogenicity of aspartame. Nonetheless, the IARC is concerned over the consumption of aspartame with respect to human health.

“The Advisory  Group  accorded  aspartame  a  high  priority  for  review  by  the  IARC Monographs  because of  its  widespread  use,  lingering  concern  over  its  carcinogenic  potential,  and  recent reports of positive findings in studies of carcinogenicity in animals,” they wrote.

Aflatoxin-containing foods

This group of toxins is formed by certain fungi found in peanuts and corn. Fungi that produce aflatoxins include Aspergillus flavus and Aspergillus parasiticus, which thrive in warm and humid regions. These fungi can contaminate crops in the field, during harvest, and while in storage.

Exposure to aflatoxins occurs when humans eat contaminated peanuts or other plant products. Exposure can also occur after eating meat or dairy from animals exposed to aflatoxin in feed. Aflatoxins increase the risk of liver cancer.

“You can reduce your aflatoxin exposure by buying only major commercial brands of nuts and nut butters and by discarding nuts that look moldy, discolored, or shriveled,” wrote the National Cancer Institute. “To help minimize risk, the US Food and Drug Administration (FDA) tests foods that may contain aflatoxins, such as peanuts and peanut butter. To date, no outbreak of human illness caused by aflatoxins has been reported in the United States, but such outbreaks have occurred in some developing countries.”

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