In a recently published study Cancer Screening and PreventionResearchers reviewed current knowledge about the beneficial and harmful effects of dietary patterns and dietary supplements on cancer risk.
To work: Diet and Supplements for Cancer PreventionImage Credit: Josep Suria/Shutterstock.com
Background
In addition to lifestyle choices, an important modifiable risk factor for cancer is diet. An increasing number of studies report not only a preventive but also a causal role of diet in cancer.
It is known that an unhealthy diet consisting of high-calorie foods, sugary drinks, processed and red meats, and foods rich in saturated and trans fats increases the risk of obesity, metabolic disorders and various types of cancer.
Obesity-related cancer mortality is 14% for men and 20% for women. Alcohol and processed meat consumption have also been linked to liver, pancreatic, and esophageal cancers, as well as colorectal cancer.
In contrast, healthy diets that include whole foods, fruits, vegetables, and whole grains reduce the risk of cancer.
In addition, dietary phytochemicals have been shown to be useful in chemoprevention due to their carcinogenesis suppressive properties and their ability to alter metastatic molecular pathways.
In this review, researchers looked at the positive and negative roles that diet and nutritional supplements play in cancer.
Diet and cancer
A large body of evidence supports a causal relationship between diet and cancer. However, the complex mechanisms of cancer have made it difficult to find direct correlations between dietary factors and cancer risk.
Additionally, although epidemiological studies have shown that consumption of certain foods is strongly linked to an increased risk of some types of cancer, factors such as timing, amount, and duration of exposure affect cellular responses, making it difficult to identify individual dietary factors that may be associated with cancer risk.
Cancer prevention guidelines have recently taken a more holistic approach, focusing on dietary patterns rather than individual foods. Healthy dietary patterns have been linked to lower risks of colon and breast cancer.
Although there is insufficient evidence to link red and processed meats to gastrointestinal cancer, processed meats such as salted, smoked or fermented meats, as well as red meat such as beef, are believed to increase the risk of cancer.
Although research on the relationship between various foods and cancer risk is limited, numerous studies have reported that alcohol consumption increases the risk of liver and esophageal cancer.
However, based on current research, the World Cancer Research Fund recommends a diet rich in vegetables, fruits and whole, unprocessed foods to reduce the risk of cancer and all forms of death.
Additionally, manipulations of dietary patterns are being studied as potential cancer treatments. Ketogenic diets, consisting of high-fat, low-carbohydrate foods, are being investigated for their ability to target the metabolism of cancer cells and improve prognosis.
Cancer and dietary supplements
The review also examined the role of various dietary components and supplements on cancer.Dietary fats are composed of mono-, poly-, and saturated fatty acids.
Polyunsaturated fatty acids, such as omega-3, are thought to have anti-cancer properties. Omega-3 fatty acids are found primarily in marine fish and in small amounts in plants such as flaxseed.
Docosahexaenoic and eicosapentaenoic acids are two omega-3 fatty acids with known anti-inflammatory properties, and studies have reported that these two fatty acids can reduce the risk of colorectal cancer by 24%.
Additionally, although clinical trials have shown a link between eicosapentaenoic acid supplementation and a reduction in adenomatous polyps, more research is needed to understand the effects of fatty acid supplementation and dosage.
The roles of micronutrients such as selenium, folate, vitamins D, C, A and E, calcium and magnesium in cancer have also been studied. Studies have found that folate has a dose-dependent relationship with cancer, with certain levels of folate having beneficial effects but high doses being carcinogenic.
Similarly, vitamins C, A, D and E, and selenium are also stated to have antioxidant properties that may be beneficial against cancer; however, taking excessive amounts of these supplements can be harmful.
Results from studies examining the link between mineral supplements and cancer risk have also suggested that a balanced intake of micronutrient supplements may be beneficial. However, excessive micronutrient supplementation may be harmful.
The review also looked at the role of polyphenols in cancer prevention. Polyphenols such as curcumin and resveratrol have been linked to antioxidant and anti-inflammatory effects, and curcumin has been investigated for its role in cell cycle arrest and apoptosis for potential cancer treatment.
Results
Overall, the findings showed that diet and nutritional supplements are important modifiable risk factors for cancer.
A healthy diet rich in whole foods, avoiding processed meats, fried foods and sugary drinks, and low alcohol consumption are recommended to reduce the risk of developing various types of cancer.
The role of dietary supplements in reducing cancer was largely beneficial but dose dependent. Excessive supplementation levels, particularly for micronutrients, were found to be harmful and researchers believe more research is needed on the health effects of dietary supplements.