The Power of Nutrition: How Diet Shapes Long-Term Breast Cancer Survival
By Dr. Kirsten West, ND, LAc, FABNO
In the years I have been in practice, it has become clear that diet and nutrition are key factors in cancer treatment, prevention, and long-term survival. Two important studies have been released recently that reinforce the link between diet and nutrition and long-term breast cancer survival specifically.
Not surprisingly, they both point to a diet high in vegetables and fruits, while being mindful of the amount and quality of carbohydrates. It is important to remember that no one diet fits every survivor’s nutritional needs, but these studies offer some good basic guidance.
Both studies were funded in part by the American Institute for Cancer Research (AICR) and led by nutritional epidemiologist Maryam Farvid, PhD. Approximately 250,000 women participated in the large Nurses’ Health Studies. Participants joined either in 1976 or 1989. All women were cancer-free and 55 or younger when they joined the study, meaning some had been participating for up to 30 years at the time of publication. By 2011, nearly 9,000 study participants had been diagnosed with breast cancer, and about 2,500 had died. [1]
Fruits & Vegetables
Women in both studies regularly answered questions about their dietary habits, family history, activity, and other cancer risk factors. The first study, published in the journal Cancer Research, focused on the link between overall vegetable and fruit intake.
The study showed that women who ate the greatest amounts of fruits and vegetables after their breast cancer diagnosis had a 21% lower risk of dying from any cause compared to those who ate the least amounts. [1]
Predictably, overall vegetable intake had the greatest effect on survival rates, with cruciferous vegetables (such as broccoli, cauliflower, and Brussels sprouts) and leafy greens being among the best. Women who ate a full serving of cruciferous vegetables daily had a 13% lower risk of dying from any cause during the study than those who didn’t eat any.
The study found that whole fruits alone didn’t significantly impact mortality, except for blueberries. Whole blueberries may be linked to a lower risk of dying from cancer or any other cause. Maryam Farvid suggested that this could be due to the antioxidants and other nutrients in the berries, but relatively few participants ate high amounts of blueberries. More research is needed, but it’s an intriguing result. [1]
Furthermore, the study drew a specific link between drinking apple juice and an increased risk of dying from breast cancer. The participants who consumed the highest amounts of apple juice drank an average of one cup per week. Apple juice was evaluated separately from other juices, which were combined into a second category. Apple juice clearly increased the risk of dying from breast cancer compared to other types. [1] This could be due to the high sugar content found in juice, which can lead to metabolic imbalances and hasten disease progression. Even vegetable juice is high in sugar.
The study separated women into subgroups based on their habits and dietary patterns. These characteristics included total fruit intake, total vegetable intake, age at diagnosis, BMI, physical activity, daily alcohol consumption, daily fiber consumption, daily animal fat consumption, total fat intake as a percentage of calories, total calorie intake, and whether participants were current smokers or had ever used oral contraceptives or postmenopausal hormones. Participants completed questionnaires every four years after diagnosis. [2]
Carbohydrates
The second study, published in Cancer Epidemiology, Biomarkers & Prevention, focused on the types and amounts of carbohydrates participants consumed. We know that carbs, and the insulin release they trigger, may promote cancer growth. [3]
This study measured the impact of glycemic index, glycemic load, insulin index, and insulin load on breast cancer survival. Like the previous study, participants completed dietary questionnaires every four years.
Quality foods matter. Highly processed foods, including sugar and sugar substitutes, contribute to obesity and health problems linked to inconsistent blood sugar and insulin levels. The study found that women who ate foods with a higher glycemic load and glycemic index were at a higher risk of dying from cancer or any cause during the study. [3] The glycemic load measures food’s impact on blood glucose, taking into account all the carbs in a food. The glycemic index assigns a numeric score (0 to 100) to a food based on how dramatically it raises blood sugar.
For glycemic load, a low ranking is 10 or below, medium is 11-19, and high is 20 or more. For example, raw broccoli has a glycemic index ranking of 15 and a glycemic load rank of 0.5. Compare that to a slice of processed white bread, which has a glycemic index ranking of 90 and a glycemic load of 43.9. [4] Glycemic load can be sneaky—carrots, for example, have a higher glycemic index than ice cream, and carrot juice has an even higher glycemic load.
The insulin ranking index showed similar findings, with higher insulin-raising diets associated with an increased risk of dying from any cause compared to those who ate lower insulin-raising diets. Fiber may have also contributed to longer survival during the study period. [1]
Study Limitations
The studies did identify some limitations, which warrant further research. The participants were primarily white, so the findings may not directly apply to other racial or ethnic groups. Additionally, the studies didn’t account for how a cancer recurrence or another disease may have affected what women ate. [1] However, these findings provide helpful guidance for the more than 3 million breast cancer survivors living in the United States today.
One Size Does Not Fit All
It’s important to remember that each individual’s breast cancer and dietary needs are unique. Every person and every cancer is different, creating a unique dynamic. The most effective way to identify the best diet for each person is through lab tests, epigenetics (closely tied to ancestry), and tumor characteristics.
When we don’t have access to the best information from testing, I generally recommend a low-carb, Mediterranean diet. This diet has the strongest research backing to date. It’s rich in whole foods, high amounts of olive oil and olives, nuts and seeds, herbs and spices, clean proteins, some fruits, and plenty of vegetables. Furthermore, these studies clearly show that diet matters—steering clear of sugars and processed carbs is key.
There are many other therapeutic forms of eating, including ketogenic, vegetarian, paleo, and carnivore diets. The ketogenic diet can be quite therapeutic as an alternative option. However, it must be done wisely, with the help of a well-versed ketogenic practitioner, and it must make sense given an individual’s epigenetics and unique terrain.
If a ketogenic diet isn’t appropriate, there are other ways to reach ketosis. One proven routine is intermittent fasting, which I believe everyone should incorporate into their lives. It can be helpful despite individual differences, and there are many ways to incorporate it.
Dietary intake plays a major role in breast cancer survivorship and prevention. We can identify the best nutritional intake for a given individual, and any given cancer, through testing and assessment.
For example, triple-negative breast cancer is often referred to as “diabetes of the breast.” Hormone-positive cancers are likely driven by metabolic issues and stress—both of which play a big role in glucose management. We often see patterns that point to these issues once testing and assessments are complete. There is no single cause, but we know that the interaction between terrain and the environment can lead to either “dis-ease” or wellness.
We must also remember that food is meant to be communal and shared with those we love. It ties into emotions and nurturing, which begin in childhood. Fostering that connection is important—what we eat should not be separate from who we share it with.
The bottom line is that dietary intake must be individualized—there is no one-size-fits-all diet. Test, assess, and address! And when in doubt, imagine you live with those you love most—your tribe—on the shores of Greece.
- Nelson, M. R. (2021, March 18). Two new studies suggest diet can help breast cancer survivors live longer. American Institute for Cancer Research. https://www.aicr.org/news/two-new-studies-suggest-diet-can-help-breast-cancer-survivors-live-longer/
- Aacrjournals.org. (n.d.). https://aacrjournals.org/cancerres/article/80/22/5134/645894/Postdiagnostic-Fruit-and-Vegetable-Consumption-and
- Farvid MS;Tamimi RM;Poole EM;Chen WY;Rosner BA;Willett WC;Holmes MD;Eliassen AH; (n.d.). Postdiagnostic dietary glycemic index, glycemic load, dietary insulin index, and insulin load and breast cancer survival. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology. https://pubmed.ncbi.nlm.nih.gov/33219162/
- Learn about the glycemic index (GI). Glycemic Index Guide. (2023, June 16). https://glycemic-index.net/
