by Over the past few decades, numerous studies have examined the connection between individual foods and nutrients and breast cancer risk.
The results strongly suggest that some dietary components (e.g. vegetables, fiber) are protective, while others (e.g. red meat, alcohol) may increase the likelihood of developing breast cancer.
However, these studies do not consider the combined effects of an entire dietary pattern in which foods, nutrients, and other dietary components interact with one another.
While researchers have examined dietary patterns and breast cancer risk, the World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) concluded in their joint opinion from 2018 that the evidence for a connection between the two was inconclusive.
Meanwhile, research suggests that a combination of healthy habits provides even greater protection against breast cancer than healthy lifestyle habits in isolation.
Now the results of a comprehensive updated research review add to the growing evidence that this is particularly the case in postmenopausal women. Here’s what you should know.
The latest research
The updated review was part of the global Continuous Update Project (CUP), an ongoing program that analyzes research on how diet, diet and physical activity affect cancer risk.
Findings from new research are constantly being added to the CUP. An independent panel of experts then evaluates and interprets the data in order to draw judgments and conclusions for cancer prevention.
The new CUP review, published online last month in the American Journal of Clinical Nutrition, included 84 studies over 22 years, most of which were conducted in North America and Europe.
Researchers examined the association between breast cancer risk and adherence to a dietary pattern alone or in combination with lifestyle behaviors.
Evidence of breast cancer risk was assessed for all women (ie, studies in which menopausal status was not reported) and also separately for premenopausal and postmenopausal women.
A healthy lifestyle offers greater benefits
Overall, higher adherence to healthy lifestyle habits, which included a healthy diet and other lifestyle factors, was consistently associated with a lower risk of breast cancer, and the evidence was rated as “strong likely.”
The results from studies that looked solely at dietary habits were less consistent and the evidence was taken into account limited, meaning it was either suggestive or inconclusive.
The combined dietary and lifestyle patterns were based on advice to maintain a healthy weight, be physically active, eat a healthy diet, and consume moderate to no alcohol.
Lifestyle patterns specific to cancer prevention (e.g., WCRF/AICR and American Cancer Society lifestyle scores) included certain dietary components that were associated with lower cancer risk.
However, only higher adherence to WCRF/AICR and American Cancer Society lifestyle patterns was consistently associated with lower breast cancer risk in all and postmenopausal women; The evidence was rated as “strongly probable.”
There have been fewer studies on lifestyle patterns and breast cancer risk in premenopausal women; The evidence was considered limited but suggestive.
How diet can help protect against breast cancer
Healthy eating habits are thought to reduce inflammation and oxidative stress in the body, factors that are thought to play a role in the development and progression of breast cancer.
Following a healthy diet can also help control insulin and insulin-like growth factors, hormones linked to breast cancer risk.
What is (and is not) part of a cancer prevention diet?
One dietary pattern associated with an overall lower risk of cancer focuses on plant-based foods—vegetables, fruits, whole grains (at least half the daily amount of grains), beans (including soybeans), and lentils.
When it comes to vegetables and fruits, the American Cancer Society recommends eating 2.5 to 3 cups of vegetables and 1.5 to 2 cups of fruit daily. This is similar to the Canadian Cancer Society’s recommendation to fill half of your plate with vegetables and fruits at every meal.
Variety is also important.
To consume a wide range of nutrients and protective phytochemicals include dark greens (e.g. spinach, rapini, arugula), orange (e.g. carrots, sweet potatoes, winter squash), cruciferous vegetables (e.g. broccoli, cauliflower, Brussels sprouts) and allium (e.g. garlic, onions) vegetables. Vary the types of fruit in your daily diet.
A diet rich in plant foods is also rich in fiber. WCRF and AICR recommend consuming at least 30g of fiber from whole foods daily.
Red meat is limited to three servings per week (12 to 18 ounces total). Processed meat should be eaten sparingly, if at all.
Highly processed foods (e.g., fast food, commercial baked goods, ready-to-eat or heatable foods) must be limited. Sugary drinks should be avoided.
To prevent cancer, it is best not to drink alcohol. If you choose to drink, the Canadian Cancer Society recommends no more than two standard drinks per week (a standard drink is 5 ounces of wine, 1.5 ounces of 40 percent spirits, or 12 ounces of 5 percent beer).
Leslie Beck, a Toronto-based private nutritionist, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD
