What is Cancer?
Before we go further and discuss the strategies that can be implemented to lower your risk of cancer, it’s helpful to understand what exactly cancer is and how it progresses in the body. In the simplest of terms, cancer is uncontrolled cell growth. Under normal circumstances, the genes inside our cells tell it when to grow, divide, and die (2). However, sometimes these cells don’t get the right messages and begin dividing uncontrollably, or do not die when they are supposed to, resulting in a tumor (2). A tumor becomes malignant (or cancerous) when it begins to spread into other tissues and organs, affecting how they function (2).
Modifiable Cancer Risk Factors
Some risk factors for cancer, such as age and genetic predisposition, cannot be altered. However, many others can and are referred to as modifiable risk factors. These factors include (ref):
· Tobacco use
· Alcohol consumption
· Excess body weight
· Physical activity
· Healthy eating
While the first four modifiable risk factors are reasonably straight-forward to implement, understanding the type of diet that confers the greatest cancer protection is less clear, especially in an era where fad and celebrity diets dominate. In the following sections, we’ll take a closer look at how what we eat (or in some cases, don’t eat) influences our risk for cancer.
Dietary Recommendations for Preventing Cancer
The World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) have released a set of dietary recommendations (3) that have been demonstrated to significantly lower the risk of developing cancer. These recommendations have been summarized in the following section:
Eat Whole Grains, Vegetables, Fruit, & Beans
The WCRF/AICR recognize that a dietary pattern rich in whole grains and dietary fibre is protective against overweight and obesity, as well as various types of cancer (especially strong evidence exists for the protective role of whole grains and fibre in the prevention of colorectal cancer). These organizations encourage the consumption of at least 30 g of dietary fibre per day, along with 400 g each of fruits and vegetables, noting that diets with the greatest cancer protection are those that feature predominantly foods of plant origin.
Limit “Fast Foods”
While an occasional burger and fries is unlikely to influence our health, eating a diet comprised of mostly processed foods that are high in fat, sugar, and salt can displace healthier foods from our diet and lead to an excessive calorie intake and weight gain over time, increasing cancer risk.
Limit Consumption of Red and Processed Meat
There is convincing evidence to suggest that excessive intakes of red meat (pork, beef, and lamb) can increase the risk for colorectal cancer. The AICR/WCRF advises limiting intake of red meat to a maximum of 12-18 ounces cooked per week (as this amount has not been associated with a measurable increase in the risk of colorectal cancer). However, when it comes to processed meat (deli meat, hot dogs, sausages, bacon), science suggests that cancer risk increases even at very low intakes. Therefore, it’s best to avoid these foods.
Limit Consumption of Sugar-Sweetened Drinks
The rationale behind limiting sugary beverages is to reduce calorie intake and prevent weight gain given that excess body weight has been linked to the development of several types of cancer.
Limit Alcohol Consumption
Alcohol (especially red wine) often gets a free pass when it comes to discussions on nutrition and health. But when it comes to cancer risk, there is no safe level of intake, with nearly six types of cancers linked to the consumption of alcohol in a dose-dependent manner.
Foods that Fight Cancer
No single food is fully protective against cancer. However, there are several foods with anti-cancer properties that, when consumed as part of an overall healthy diet pattern, can significantly and synergistically lower the risk for cancer in later life (4). The most well-researched of these foods are:
Broccoli, Brussels sprouts, rapini, cabbage, cauliflower, turnips, kale, and collard greens belong to the cruciferous family of vegetables that contain several anti-cancer properties with antioxidant/anti-inflammatory effects that keeps DNA healthy and slow the progression of cancer.
Nutrition headlines seem to dance back and forth between coffee being good vs. bad for our health. However, brewed coffee contains many phytochemicals with potent antioxidant activity and the WCRF/AICR have concluded that there is strong, probable evidence that coffee lowers the risk of both endometrial and liver cancer. Specific recommendations have not been established by the AICR/WCRF. As such, it’s best to limit caffeine intake to 400 mg per day, which is the equivalent of three 8 oz. cups of coffee (5).
Legumes or pulses, which includes beans, lentils, and split peas, are arguably one of the most nutrient-dense foods available in our diet. Not only are legumes an excellent source of dietary fibre and plant protein, they also contain many anti-cancer properties, such as lignans, saponins, resistant starch, and antioxidants. Legumes have been linked to a lower risk of cancer (specifically colorectal cancer and possibly breast and prostate cancer) as they promote a healthy body weight, protect colon cells and DNA from oxidative damage, and help to regulate cell growth.
Soy foods, including tofu, tempeh, edamame, soymilk, and miso, contain phytoestrogens that demonstrate weak estrogenic activity in the body. Because excess estrogen has been linked to an increased risk of breast cancer, initial concern was raised that soy could increase the risk of cancer in humans and indeed, some preliminary studies on rats and mice showed that soy increased estrogen receptor positive (ER+) breast cancer cells. However, subsequent research has revealed that rodents are unable to metabolise soy in the way that humans do, which leads to an excess accumulation of active phytoestrogens that are not seen in humans.
Overall, human studies show that soy does not increase cancer risk and may actually lower risk by decreasing cell growth and promoting tumor destruction.
While there are countless teas available on the market, authentic tea (which comes from the leaves, roots, seeds, or flowers of plants) can be divided into four categories: black, green, oolong, and white. While data on the link between tea and cancer development is too inconsistent to reach a firm conclusion, studies show that a polyphenol found in green tea may decrease the development of several cancers by stimulating enzymes that halt cancer growth, increasing the self-destruction of cancer cells, and preventing the spread of cancer to other parts of the body.
Berries are rich sources of fibre and vitamin C, which have been linked with a lower risk of esophageal and colorectal cancer, respectively. Raspberries and strawberries also contain the phytochemical ellagic acid, which been linked to a reduced risk of skin, bladder, lung, esophagus, and stomach cancer. In addition, blueberries are a rich source of anthocyanosides, which are the most potent antioxidant discovered to date.
References: 1. World Health Organization. Cancer. Sep 2018. Available from: https://www.who.int/news-room/fact-sheets/detail/cancer
2. Canadian Cancer Society. What is cancer? n.d. Available from: https://www.cancer.ca/en/cancer-information/cancer-101/what-is-cancer/?region=on
3. World Cancer Research Fund/American Institute for Cancer Research. Diet, Nutrition, Physical Activity and Cancer: A global Perspective. Continuous Update Project Expert Report 2018. Available from: https://www.aicr.org/reduce-your-cancer-risk/recommendations-for-cancer-prevention/index.html
4. American Institute for Cancer Research (AICR). AICR’s Foods that Fight Cancer. n.d. Available from: https://www.aicr.org/foods-that-fight-cancer/
5. Dietitians of Canada. What is caffeine? Is it bad for me health? Mar 2016. Available from: https://www.dietitians.ca/Downloads/Factsheets/What-is-caffeine.aspx