Large international cohort data suggest that plant-forward dietary patterns and specific micronutrients may be associated with reduced breast cancer risk and improved survival, highlighting that diet is a potentially modifiable factor worthy of further investigation.

study: Plant-based dietary patterns, micronutrient status, and breast cancer outcomes: a joint analysis of the UK Biobank and China Longitudinal Health and Longevity Study. Image credit: Pixel-Shot / Shutterstock

In a recent study published in the journal Frontiers of nutritionResearchers investigated whether adherence to a healthy plant-based diet and intake of certain micronutrients was associated with breast cancer risk and mortality in breast cancer patients.

Their findings suggest that higher adherence to a healthy plant-based diet is associated with lower breast cancer risk and lower mortality after diagnosis. Higher intakes of calcium, vitamins B2 and C, magnesium, and phosphorus, but not breast cancer incidence, were associated with lower mortality risk, whereas higher sodium intake was associated with increased mortality risk. These associations are observational and do not establish causation.

Background: Diet as a modifiable risk factor for breast cancer

Despite improvements in screening and treatment, the global burden of breast cancer continues to increase, highlighting the importance of identifying modifiable risk factors.

Diet is increasingly recognized as a potentially important determinant of both cancer development and prognosis. Plant-based eating patterns such as the Alternative Mediterranean Diet (amed) and the Healthy Plant-Based Diet Index (H.P.D.I.), emphasize whole grains, vegetables, fruits, legumes, and other nutritious plant foods while avoiding processed foods and red meat.

A plant-based diet is rich in antioxidants, fiber, and bioactive compounds. anti-inflammatory and anti-cancer effect. However, these biological mechanisms are still only plausible hypotheses rather than the causal pathways proven in this study. Previous studies have suggested that these diets are associated with a reduced risk of breast cancer, but evidence regarding their impact on survival after diagnosis remains limited and inconsistent.

Furthermore, most studies focus on overall dietary patterns without disentangling the independent roles of specific micronutrients. The long-term predictive value of diet on breast cancer outcomes has also not been well investigated using advanced statistical and machine learning approaches. In this study, the AMED association was generally directionally protective but not statistically significant.

Cohort design, dietary assessment, statistical modeling

Researchers analyzed data from two prospective cohorts: the UK Biobank and the China Long-Term Health and Longevity Study (CLHLS). The UK Biobank sample included 67,045 women who did not have breast cancer at baseline and 3,397 women who did.

The CLHLS analysis included 7,431 cancer-free participants who were tracked for overall cancer rather than breast cancer-specific cancers. Dietary intake in the UK Biobank was assessed using a validated 24-hour recall, whereas a food frequency questionnaire was used in the CLHLS. These cohorts differ significantly in age structure, ethnicity, and dietary assessment approaches, which may affect comparability.

Adherence to a plant-based diet was measured using the HPDI and AMED scores. The HPDI incorporates 17 food groups and assigns positive scores to healthy plant foods and negative scores to animal foods and unhealthy plant foods. Micronutrient intakes were calculated by linking reported food intakes to a nutrient composition database. Outcomes included breast cancer incidence and all-cause mortality identified through UK Biobank national registries, while CLHLS cancer outcomes were self-reported during follow-up.

Associations were assessed using multivariable proportional hazards modeling with stepwise adjustment for demographic, socioeconomic, lifestyle, and clinical factors. A restricted cubic spline model was used to assess potential nonlinear dose-response relationships.

Predictive performance was evaluated using a concordance index, a random forest model, and 3-, 5-, and 10-year time-dependent receiver operating characteristic curves.

Key findings: dietary patterns, micronutrients, and mortality.

Among UK Biobank participants, higher adherence to the HPDI was associated with lower breast cancer incidence and improved survival. 11% fewer women in the highest HPDI tertile more likely to develop breast cancer Compare with those in the lowest tertile. Each standard deviation increase in HPDI corresponds to a 4% decrease in risk.

Among women with breast cancer, those in the highest HPDI tertile had a 28% lower risk of all-cause mortality, and each standard deviation increase in HPDI decreased the risk of death by 11%. No significant nonlinear associations were observed.

The CLHLS cohort has a higher plant-based diet index (P.D.I.) score was significantly associated with lower overall cancer incidence, with a 39% reduction in risk in the highest and lowest groups.

Micronutrient analysis revealed that higher intakes of calcium, magnesium, copper, and vitamin C were associated with a lower risk of breast cancer. Among patients, higher intakes of calcium, phosphorus, magnesium, and vitamin B2 were associated with lower mortality rates. The relevance of these micronutrients varied across outcomes, with some primarily associated with incidence and others associated with mortality. In contrast, each standard deviation increase in sodium intake increased the risk of death by 15%.

The predictive model showed moderate discrimination overall. Micronutrients alone performed best in predicting breast cancer incidence, whereas HPDI performed best in predicting 5-year mortality. The combined model had the best performance in 10 years. Overall predictive accuracy was moderate, suggesting limited utility for immediate clinical prediction.

Interpretation, strengths, and limitations

This large prospective study found that stronger adherence to a healthy plant-based diet was correlated with lower breast cancer incidence and improved survival after diagnosis.

Several micronutrients, particularly calcium, vitamin B2, vitamin C, magnesium, and phosphorus, showed independent protective associations for incidence but not mortality, whereas sodium intake was associated with increased mortality. These findings show that plant-oriented dietary patterns and nutritious diets inflammationoxidative stress, and cancer progression, but the causal relationship is still unclear.

Key strengths include the large sample size, prospective design, use of two international cohorts, and application of multiple analytical approaches including spline models and machine learning. Simultaneous assessment of dietary patterns and individual micronutrients increases interpretability.

However, limitations of the analysis include its observational design, which precludes causal inferences. Confounding factors could not be excluded. Important risk factors for breast cancer, such as hormone therapy and childbirth, were not available. Limited ethnic diversity in UK Biobank and self-reported cancer data in CLHLS may impact generalizability. Dietary intake was assessed only at baseline, limiting the ability to assess changes in diet over time, and additional factors such as family history and detailed menopausal hormone data were incompletely captured.