July 3, 2026, 11:41 am | Read time: 3 minutes
Whether diet can influence the risk of breast cancer has been researched for years. A large long-term study with more than 93,000 women has revisited this question. The results provide new insights into the role certain foods might play in breast cancer prevention.
Certain Diets May Influence Breast Cancer Risk
Researchers wanted to determine if a diet rich in flavonoids is associated with a lower risk of breast cancer and if this association also applies to women with a higher genetic predisposition. Flavonoids are natural plant compounds found in fruits, vegetables, tea, and dark chocolate, known for their antioxidant and anti-inflammatory properties.1
The result: Women with a flavonoid-rich diet had an overall lower risk of breast cancer. Notably, this association was also found in women with a high genetic risk.
How the Study Was Conducted and What It Examined
For the study, scientists analyzed data from 93,271 women from the UK Biobank who had no cancer at the start of the study. The average age was 56 years. Participants were enrolled between 2006 and 2010 and followed for nearly 12 years. During this time, 3,110 women developed breast cancer.
Using a validated dietary questionnaire, researchers recorded the participants’ eating habits and calculated the so-called “Flavodiet Score.” This score evaluates the regular consumption of ten flavonoid-rich foods, including apples, berries, grapefruits, oranges, grapes, peppers, onions, black and green tea, dark chocolate, and red wine. Additionally, the scientists examined the intake of individual flavonoid subgroups.
Researchers also determined each participant’s genetic breast cancer risk using a risk score based on 168 genetic variants. In their analysis, they considered numerous other factors such as age, body weight, physical activity, smoking, alcohol consumption, diet, family history of breast cancer, menopausal status, and hormone replacement therapy.
Detailed Results
Women with the highest flavonoid-rich diet had a 15 percent lower risk of breast cancer compared to those with the lowest intake of flavonoid-rich foods. The higher the “Flavodiet Score,” the lower the overall risk of developing the disease.
Individual flavonoid groups were also associated with a lower breast cancer risk. The connection was particularly strong for flavanones, mainly found in citrus fruits, and proanthocyanidins, present in apples, berries, and grapes. Among individual foods, oranges and apples were notably linked to a reduced breast cancer risk.
As expected, genetic predisposition also played a significant role: Women with the highest genetic risk were much more likely to develop breast cancer than those with the lowest genetic risk. However, even among them, a risk-reducing effect was observed from consuming flavonoid-rich foods.
The results remained consistent in several additional analyses that tested the robustness of the study findings.
Also of interest: Breast Cancer – Risk Constellations Where Genetic Testing Is Recommended
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What This Specifically Means
The study suggests that a flavonoid-rich diet might be associated with a lower risk of breast cancer–even in women with a higher genetic predisposition. Researchers cite various biological effects of flavonoids as possible explanations. They may reduce oxidative stress and inflammation and influence signaling pathways involved in cancer development. However, these potential mechanisms were not directly investigated in the study.
Promising Study with Limitations
The strengths of the study include the large number of participants, the prospective study design, and the long follow-up period. Additionally, researchers examined for the first time the relationship between a flavonoid-rich diet and genetic breast cancer risk.
However, it is an observational study. Therefore, it cannot prove a causal relationship, only a statistical association. Moreover, the dietary information is based on a questionnaire, which may lead to recall errors or inaccurate reporting.