Earlier this month, the American Cancer Society (ACS) released updated lifestyle recommendations to help lower cancer risk. The advice, last updated in 2012, is based on a comprehensive review of the latest evidence.
The revised guideline places an increased emphasis eating less red meat and fewer highly processed foods and avoiding or limiting alcohol. It also increases the recommended amount of physical activity.
What to eat to prevent cancer
The ACS recommendation is to “follow a healthy eating pattern at all ages.” The foundation of a healthy eating pattern is mostly plants – vegetables, fruits, whole grains, beans and lentils, and nuts and seeds. It also includes healthy proteins, such as fish and poultry, and unsaturated fats.
The updated diet recommendation emphasizes eating a variety of vegetables, especially ones that are dark green (e.g., spinach, kale, broccoli, rapini), red (e.g., beets, red bell pepper, red cabbage, radicchio) and orange (e.g., carrots, butternut squash, sweet potato).
It also highlights including a variety of colourful whole fruit in your diet. In Canada, a low fruit intake is among the top five leading preventable causes of cancer.
To lower cancer risk, a daily intake of at least 2.5 to 3 cups of vegetables and 1.5 to 2 cups of fruit is advised.
Advice to eat whole grains, foods that are strongly tied to protection against colorectal cancer, is also emphasized as well as advice to eat pulses (e.g., black beans, kidney beans, chickpeas, lentils).
What to eat (and drink) less of
The best available evidence supports the recommendation to limit intake of red and processed meats. A high intake of both is associated with greater risk of colorectal cancer and may also play a role in breast and prostate cancers.
Since it’s not known whether there’s a safe level of intake for red and processed meat, the new guideline does not advise on consumption limits. Instead, the ACS recommends choosing fish, poultry and beans more often than red meat and to eat processed meats sparingly, if at all.
Foods high in added sugars, especially sugar-sweetened beverages, should also be limited or avoided since they’re associated with risk of obesity, which itself is linked to 13 types of cancers.
Highly processed foods, which contain little, if any, whole foods, should also be limited. These foods are typically higher in fat, contain added sugars and sodium and are lacking fibre and protective phytochemicals.
Ultraprocessed foods include chicken nuggets, chicken strips, cereal bars, granola bars, breakfast cereals, frozen waffles, cookies, potato chips, pretzels, crackers, soft drinks, candy, processed meats, frozen dinners, instant noodles, frozen pizza, fast food and more.
The revised ASC cancer prevention guideline also states “it is best not to drink alcohol” since evidence shows that any amount of alcohol increases the risk of some types of cancer, most notably breast cancer.
If you do drink, limit your intake to no more than one drink each day for women and two drinks for men. One drink is equivalent to five ounces of wine, 12 ounces of beer or 1.5 ounces of 80-proof spirits.
Being overweight or obese is clearly linked with a greater risk of several types of cancer. The ACS guideline recommends to “keep your weight within the healthy range and avoid weight gain in adult life.”
A body mass index (BMI) of 18.5 to 24.9 is defined as a healthy weight. A BMI between 25 and 29.9 is classified as overweight; a BMI of 30 or greater is considered obese. BMI is calculated as your weight in kilograms divided by your height in metres squared.
Adults are advised to get 150 to 300 minutes of moderate-intensity exercise (e.g., brisk walking, doubles tennis) a week, or 75 to 150 minutes of vigorous-intensity exercise (e.g., running, spinning, singles tennis). Hitting or exceeding the upper limit of 300 minutes is considered optimal.
Children and teens should get at least one hour of physical activity each day.
Although resistance training is recommended for overall health, there is a lack of evidence for this type of exercise in relation to cancer. For cancer prevention, the focus is on aerobic physical activity.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.
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