Many factors can contribute to the development of chronic diseases, including certain types of cancer. The link between diet and cancer risk is complicated. However, certain dietary patterns and food choices do have associations with an increased risk of cancer. This article explains how diet may influence cancer risk.

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Illustration by Diego Sabogal

Researchers have predicted that cancer will become the leading cause of death in every country in the world by the end of this century, making cancer prevention a top priority in the healthcare field.

Although many factors can influence a person’s risk of developing cancer, research shows that environmental causes, including dietary choices, can also affect cancer risk.

In the early 1960s, researchers discovered that cancer rates varied between countries and identified that specific dietary patterns have correlations with certain types of cancer.

They also discovered that cancer rates in people from countries with a low cancer risk who migrated to countries with higher cancer risk matched or exceeded the cancer rates in the country they migrated to. This suggests that diet and lifestyle strongly impacted cancer development.

Since then, researchers have narrowed down the specific foods and dietary patterns that may increase the risk of certain cancers.

This article will focus primarily on food, yet it is important to remember that alcohol intake is also a known dietary risk factor for cancer development.

Research into diet and cancer risk is ongoing, and researchers still have much to learn about how and why food choices affect cancer risk.

Red and processed meats

Scientists know there is a strong link between processed meat intake and certain types of cancer.

In 2015, the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), classified processed meat as carcinogenic and unprocessed red meat as “probably” carcinogenic.

A 2018 review found that increasing intake of processed meat up to about 60 grams (g) per day and red meat up to 150 g per day increased colorectal cancer risk by about 20%.

Diets high in processed and red meat also have associations with an increased risk of other cancers, including stomach cancer and breast cancer.

Compounds created during high-temperature cooking and smoking processes can cause cellular damage, which can initiate the development of cancerous cells. The heme iron found in red and processed meats may also have a toxic effect on cells.

Ultra-processed foods

Ultra-processed foods often contain ingredients that result from industrial processing, such as protein isolates, hydrogenated oils, high-fructose corn syrup, flavor enhancers, artificial sweeteners, and thickeners.

Examples of ultra-processed foods and beverages include ultra-processed sweet and savory snack foods, soda and energy drinks, breakfast cereals, reconstituted meat products, frozen pizzas, candy, and more.

According to health experts, diets high in ultra-processed foods, including Western diets, significantly increase the risk of certain cancers.

A 2018 study that included data on almost 105,000 people found that increasing the dietary proportion of ultra-processed foods by 10% had associations with a significant 12% increased risk of overall cancer and an 11% increased chance of developing breast cancer.

Ultra-processed foods are rich in saturated fat, added sugar, and salt but low in protective nutrients, such as fiber, vitamins, and minerals. Ultra-processed foods also contain potentially carcinogenic compounds formed during processing, such as heterocyclic amines and polycyclic aromatic hydrocarbons.

Certain food additives and contamination by chemicals from food packaging may also contribute to the increased cancer risk associated with the consumption of ultra-processed food.

In addition to cancer, ultra-processed food intake has links to many other chronic conditions, including type 2 diabetes and heart disease, and an increased risk of death from all causes. It is important to try to limit consumption of ultra-processed products as much as possible to reduce the risk of developing these conditions.

High-salt diets

A diet high in added salt may increase the risk of certain cancers, particularly stomach cancer.

Scientists have suggested that high salt intake may increase the risk of infection caused by Helicobacter pylori bacteria. H. pylori infections significantly increase the risk of stomach cancer.

Also, eating high-salt foods may lead to the production of N-nitroso compounds (NOCs). The IARC has classified many of these as “probably” carcinogenic to humans.

Diets high in added salt have associations with an increased risk of certain cancers, including stomach cancer and esophageal cancer.

Scalding beverages

Drinking scalding hot beverages may increase cancer risk. The IARC has classified beverages with a temperature over 149°F (65°C) as “probably” carcinogenic to humans.

A 2015 review of 39 studies found that drinking hot beverages has associations with a significantly increased risk of esophageal cancer, especially in South American and Asian populations.

The study found that people who usually drank very hot or hot beverages were almost twice as likely to develop esophageal cancer than those who usually consumed warm or cold drinks.

Recurrent temperature-related injuries to esophagus cells may lead to the development of precancerous and cancerous lesions.

Other possible dietary risk factors

The IARC identified several other dietary factors that may lead to cancer progression. For example, following a diet with a high glycemic load may increase the risk of endometrial cancer.

Diets with a high-glycemic load adversely affect blood sugar and may lead to chronically elevated insulin levels and insulin resistance. This may adversely affect hormone levels and lead to an increased risk of developing endometrial cancer.

Diets with a high-glycemic load are typically rich in added sugars and refined carbohydrates, such as white bread and white rice.

Aflatoxin is a compound produced by a fungus that grows in foods, such as nuts, grains, and dried fruit, stored in hot, damp conditions. The IARC considers aflatoxin carcinogenic.

Long-term exposure to aflatoxins has links to an increased risk of gallbladder cancer and liver cancer.

Scientists consider exposure to Aflatoxin a significant risk factor for liver cancer in low-income countries, especially in people who have an active hepatitis infection, which affects the liver.

Before discussing which foods and dietary patterns may protect against cancer development, it is crucial to understand that engaging in activities that scientists consider significant cancer risk factors, such as cigarette smoking or excessive drinking, may counteract the potential protective effects of diet.

Avoiding smoking, reducing alcohol intake, managing body weight, and being active, are critical to reducing cancer risk.

Researchers have discovered that, just as some dietary patterns may increase cancer risk, nutritional choices can also have a protective effect against cancer.

For example, the Mediterranean diet, which is high in fiber, antioxidants, and anti-inflammatory compounds, and low in red and processed meat and ultra-processed foods, has associations with an overall protective effect against cancer and cancer-related death.

Studies have shown that diets high in fruits, vegetables, and other fiber-rich plant foods offer protection against cancer development. This is because these foods contain compounds that help protect against cellular damage.

Consuming a varied diet that provides optimal amounts of fiber, vitamins, minerals, and beneficial plant compounds is essential for overall health and cancer risk reduction.

In addition to consuming a diet rich in plant-based foods, reducing intake of processed and red meats, ultra-processed foods, and added sugars and salt may help reduce the risk of certain cancers and many other chronic conditions.

Though many factors can influence a person’s risk of developing cancer, including factors that a person cannot control, research shows that some dietary patterns and specific foods may increase the chance of developing certain cancers.

Evidence suggests that ultra-processed foods, processed meat products, diets high in added salt, and drinking scalding beverages may increase the risk of cancer development.

Although scientists still have much to learn about how diet impacts cancer development and progression, significantly reducing or avoiding these foods and adapting dietary patterns will likely improve overall health. This may also help reduce a person’s risk of developing certain cancers.