2026 Theses Doctoral

The Impact of Dietary Patterns, Race and Ethnicity, and Acculturation Status on Breast Cancer-related Outcomes

Zhou, Yibing

Breast cancer is a leading cause of cancer death among women in the United States. While dietary patterns have been associated with cancer-related outcomes, few studies have focused on Asian American populations, despite their increasing numbers and sometimes better breast cancer survival rates. Understanding whether dietary factors contribute to these disparities in health outcomes remains an important but understudied area.

This dissertation examined dietary patterns and their associations with breast cancer recurrence and all-cause mortality, with a focus on Asian American women in comparison to non-Hispanic White women. It also explored the role of acculturation on dietary habits and health outcomes.

The Pathways Study, a prospective cohort study of over 4,500 women diagnosed with breast cancer, provided the data used to address the aims. Asian American and non-Hispanic White participants with available dietary data were included. Dietary intake was assessed using a 139-item food frequency questionnaire and analyzed using principal component analysis to identify dietary patterns. Acculturation status was measured using eight proxy variables from the baseline questionnaires. Cox proportional hazards models were performed to examine associations between dietary patterns and breast cancer outcomes, and between acculturation and these outcomes. Linear regression was used to assess the relationship between acculturation and dietary patterns.

Five dietary patterns were identified: High Vegetable, High Legume, Low Red Meat, High Seafood, and Low Coffee and Alcohol. Asian American women who had the highest level of adherence to the High Legume pattern were associated with significantly lower risks for all-cause mortality (Hazard ratio=0.48, 95% CI= 0.25-0.91, p=0.026) and breast cancer recurrence (Hazard ratio=0.49, 95% CI=0.26-0.93, p=0.029) compared to those who had the lowest level of adherence. In practice, this would be equivalent to a difference of around 1/4 to 1/3 cup of legumes per day.

There were a variety of dietary pattern differences among the Asian subgroups. Indian Americans adhere to an overall plant-forward dietary pattern with higher adherence to the High Legume pattern than Chinese and Filipina Americans; as well as higher adherence to the Low Red Meat pattern than Chinese, Filipina, Japanese, and Vietnamese Americans. Filipina Americans had significantly higher adherence to the High Seafood pattern than Chinese, Asian Indian, and Japanese Americans. Chinese Americans had significantly lower adherence to the Low Coffee and Alcohol pattern compared to Filipina, Asian Indian, Japanese, and Korean Americans. Higher acculturation level was associated with lower adherence to the High Vegetable, High Seafood, Low Red Meat, and Low Coffee and Alcohol patterns among the Asian participants. A significant interaction between the High Vegetable pattern and acculturation was observed (HR=1.14, 95% CI=1.03-1.28, p=0.017), which suggested that the association between the High Vegetable pattern and all-cause mortality differed by acculturation level.

These findings highlighted meaningful differences in dietary patterns across racial and ethnic groups and within Asian American subgroups. Certain plant-based dietary patterns, such as those high in legumes from protein and vegetable sources, may be associated with more protective effects for breast cancer outcomes. Acculturation appeared to influence dietary behaviors and may modify the relationship between diet and all-cause mortality among Asian American breast cancer survivors, such that those who were more acculturated experience a weakened protective effect of the High Vegetable pattern. Although clinical factors, such as age at diagnosis, cancer stage, and hormone receptor status, remained the strongest predictors for breast cancer-related outcomes, these results underscored the importance of considering cultural dietary patterns and acculturation in future research on cancer survivorship among Asian populations.