In a recent study published in Cancer Screening and Prevention, researchers reviewed the existing knowledge on the beneficial and detrimental effects of dietary patterns and nutritional supplements on cancer risk.
Study: Diet and Supplements in Cancer Prevention. Image Credit: Josep Suria/Shutterstock.com
Background
A major modifiable risk factor for cancer, apart from lifestyle choices, is diet. A growing number of studies are reporting not only the preventative but also the causal role of diet in cancer.
Unhealthy diets consisting of high-calorie foods, sugar-sweetened beverages, processed and red meats, and foods rich in saturated and trans-fats are known to increase the risk of obesity, metabolic disorders, and various forms of cancers.
The rate of cancer-related deaths linked to obesity is 14% among men and 20% among women. The consumption of alcohol and processed meats has also been associated to cancers of the liver, pancreas, and oesophagus, as well as colorectal cancer.
In contrast, healthy dietary patterns involving whole foods, fruits, vegetables, and grains have reduced cancer risk.
Furthermore, dietary phytochemicals have also been useful in chemoprevention, as they have exhibited carcinogenesis-suppressing properties and the ability to change metastatic molecular pathways.
In the present review, the researchers discussed diet and nutritional supplements' beneficial and detrimental roles in cancer.
Diet and cancer
A large body of evidence supports a causal association between diet and cancer. However, the complex mechanisms of cancer have presented challenges in finding direct correlations between cancer risk and dietary factors.
Furthermore, while epidemiological studies have shown that consumption of specific foods is strongly linked to an elevated risk of some forms of cancer, factors such as the timing, quantity, and exposure length impact the cellular responses, making it difficult to identify individual dietary factors that can be linked to cancer risk.
Cancer prevention guidelines have recently adopted a more holistic approach focusing on dietary patterns rather than individual foods. Healthy eating patterns have been associated with lower risks of colon and breast cancers.
Although the evidence linking red and processed meats to gastrointestinal cancer is not substantial, processed meats such as cured, salted, smoked, or fermented meats, as well as red meats such as beef, are believed to increase the risk of cancer.
Although the research on the association between various foods and cancer risk is limited, many studies have reported an increased risk of liver and oesophagal cancer due to alcohol consumption.
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-cause mortality.
Furthermore, manipulations of dietary patterns are also being examined as potential cancer treatment methods. Ketogenic diets consisting of high-fat and low-carbohydrate foods are being explored for the ability to target the metabolism of cancer cells and improve prognosis.
Cancer and dietary supplements
The review also examined the role of various nutritional components and supplements in cancer. Dietary fats consist of mono- and poly-unsaturated and saturated fatty acids.
Polyunsaturated fatty acids such as omega-3 have been attributed to anti-cancer properties. Omega-3 fatty acids can be found mainly in marine fish and small quantities in plants such as flaxseed.
Docosahexaenoic and eicosapentaenoic acid are two omega-3 fatty acids with known anti-inflammatory properties, and studies have reported that these two fatty acids could reduce colorectal cancer risk by 24%.
Furthermore, while clinical trials have shown a link between eicosapentaenoic acid supplementation and reductions in adenomatous polyps, further research is required 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 examined. Studies have found that folate has a dose-dependent relationship with cancer, with specific folate levels having beneficial effects but high doses being carcinogenic.
Similarly, vitamins C, A, D, and E, and selenium have exhibited anti-oxidant properties that might be beneficial against cancers, but taking these supplements in excess levels could be harmful.
Results from studies examining the link between mineral supplements and cancer risk also suggested that a balanced intake of micronutrient supplements might be beneficial. Still, excess supplementation of micronutrients can be harmful.
The review also discussed 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 explored for its role in cell cycle arrest and apoptosis for potential cancer treatment.
Conclusions
Overall, the findings indicated that diet and nutritional supplements were major modifiable risk factors for cancer.
A healthy diet rich in whole foods and devoid of processed meats, fried foods, and sugar-sweetened beverages was recommended to lower the risk of various types of cancers, along with low alcohol intake.
The role of dietary supplements in lowering cancer was largely beneficial but dose-dependent. Excess levels of supplementation, especially for micronutrients, were found to be harmful, and the researchers believe that more research is required on the effects of dietary supplements on health.
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