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Diet and Cancer

Learn more about the link between diet and cancer including data and myths.
© University of Turin

The World Health Organization estimated that up to 30% of cancer-related deaths could be prevented by modifying lifestyle, including diet and physical activity patterns.

While the link between cancer and diet is far from being fully understood, a growing body of evidence has reported that certain foods and nutrients may lower the risk of—or, conversely, contribute to—certain types of cancer.

Some risk factors related to cancer development, such as genetics and environment, are unmodifiable. However, it has been estimated that they represent less than 30% of a person’s lifetime risk of getting cancer. Preventing obesity and following a healthy dietary pattern should be part of the recommendations to both the general population and cancer survivors as these strategies are convincingly linked to a reduced risk of primary or secondary cancers.

Over the past few decades, a growing number of observational studies have linked different dietetic patterns to some types of cancers. Obesity, for example, has been linked to aggressive prostate cancer as well as oral and pharynx cancers. Additionally, an increased risk of stomach cancer has been linked to salted preserved foods and alcohol consumption, which is also associated with kidney cancer. The risk of oesophagus cancer has been linked to consuming very hot drinks. The expert panels also concluded that a diet with a high-glycaemic load probably increased the risk of endometrial cancer.

On the other hand, several dietary factors can reduce the risk of several cancers, such as colorectal cancer. Coffee, for example, was found in one study to probably be protective for liver and endometrial cancer, but these observations were judged too strong by some researchers and potentially affected by some methodological bias. While definitive conclusions cannot be drawn in this field, some considerations are worth noting:

What About the Connection Between Processed Meat and Red Meat With Cancer?

Eating around 50 grams a day of processed meat is associated with about a 20% increase in colorectal cancer risk. Growing evidence is showing that colorectal cancers can be attributed to the breakdown of the protective mucosal barrier of the gut.

Furthermore, colorectal carcinogenesis has also been linked to inflammation and oxidative stress in the colic epithelium. Overall, consuming processed meats, red meats, and alcohol, as well as smoking, physical inactivity, and obesity, is associated with colorectal cancer, revealing the aetiological importance of the gut microbiome and its composition.

Are Sugary Drinks Linked to an Increased Risk of Cancer?

Carbohydrates with a high-glycaemic index (a measure of how fast carbohydrates turn into sugar in the blood), such as those contained in sugar-sweetened soft drinks, have been associated with a greater risk for prostate cancer and lung cancer. Conversely, the consumption of carbohydrates with a low-glycaemic index (such as those contained in lentils, and peas) were associated with a lower risk of prostate and colorectal cancers.

Can Fruit and Vegetables Be Important Determinants of Cancer Risk?

Findings have evolved in recent years – from early case-control studies indicating higher intakes of fruit and vegetables were associated with a lower risk of several types of cancer to subsequent prospective studies producing weaker findings.

The 2018 World Cancer Research Fund, for example, reported that neither fruits nor vegetables were considered to be convincingly or probably associated with the risk of any cancer. There has been suggestive evidence of specific components of certain fruits and vegetables that might possess protective properties against some types of cancers.

Do Vitamins and Minerals Reduce Cancer Risk?

Higher levels of consumption of vitamin or mineral supplements have not been linked to reducing cancer risk in well-nourished populations. In fact, this might increase cancer risk. For example, high consumption of β carotene might increase the risk of lung cancer.

Although vitamin and mineral supplements can be important for other aspects of health, they should not be used for cancer prevention. Of course, deficiencies of vitamins and essential minerals cause a decline in health, including increased vulnerability to some types of cancer, but details of these adverse effects still need further investigation.

Authors: Dr. Savino Sciascia, and Dr. Gregory Winston Gilcrease.

© University of Turin
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