Plant-based diet, inflammation biomarkers and body composition among women with breast cancer: the Pathways Study

Abstract

The World Cancer Research Fund and the American Institute for Cancer Research recommend a plant-based diet to cancer survivors, which may reduce chronic inflammation and excess adiposity associated with worse survival. We investigated associations of plant-based dietary patterns with inflammation biomarkers and body composition in the Pathways Study, in which 3659 women with breast cancer provided validated food frequency questionnaires approximately 2 months after diagnosis. We derived three plant-based diet indices: overall plant-based diet index (PDI), healthful plant-based diet index (hPDI) and unhealthful plant-based diet index (uPDI). We assayed circulating inflammation biomarkers related to systemic inflammation (high-sensitivity C-reactive protein [hsCRP]), pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and anti-inflammatory cytokines (IL-4, IL-10, IL-13). We estimated areas (cm²) of muscle and visceral and subcutaneous adipose tissue (VAT and SAT) from computed tomography scans. Using multivariable linear regression, we calculated the differences in inflammation biomarkers and body composition for each index. Per 10-point increase for each index: hsCRP was significantly lower by 6·9 % (95 % CI 1·6%, 11·8%) for PDI and 9·0 % (95 % CI 4·9%, 12·8%) for hPDI but significantly higher by 5·4 % (95 % CI 0·5%, 10·5%) for uPDI, and VAT was significantly lower by 7·8 cm² (95 % CI 2·0 cm², 13·6 cm²) for PDI and 8·6 cm² (95 % CI 4·1 cm², 13·2 cm²) for hPDI but significantly higher by 6·2 cm² (95 % CI 1·3 cm², 11·1 cm²) for uPDI. No significant associations were observed for other inflammation biomarkers, muscle, or SAT. A plant-based diet, especially a healthful plant-based diet, may be associated with reduced inflammation and visceral adiposity among breast cancer survivors.

Keywords: Body composition; Breast cancer; Inflammation; Plant-based diet.

Figure 1.

Adjusted^† associations of plant-based Indices (per 10-point increase) with relative changes (%) of inflammatory biomarkers ^{‡ §}. hPDI, healthful plant-based diet index; PDI, overall plant-based diet index; uPDI, unhealthful plant-based diet index. ^†Multiple linear regression were adjusted in separate models for (1) demographic and clinicopathological factors: age (years), race and ethnicity (American Indian/Alaska Native, Asian/Pacific Islander, Black, Hispanic, non-Hispanic White), education (high school or less, some college, college graduate, postgraduate, unknown), income (<$50 000, $50 000–$89 999, ≥$90 000, unknown), marital status (married, single, unknown), menopausal status (premenopausal, postmenopausal), stage (I, II, III, IV), ER (positive, negative, unknown), PR (positive, negative, unknown), HER2 (positive, negative, unknown) and Elixhauser comorbidity index (0, 1, 2, ≥3, unknown); (2) lifestyle factors: total energy intake (kcal/d), BMI (kg/m²), physical activity (MET-h/week) and smoking status (never, former, current, unknown); and (3) blood collection and processing-related factors: season of blood draw (Jan–Mar, Apr–Jun, Jul–Sep, Oct–Dec), time of blood draw in relation to breast cancer treatment received (prior to any treatment, after neoadjuvant chemotherapy before surgery, after surgery before adjuvant chemotherapy, after surgery and chemotherapy (with or without radiation or hormonal therapy), after radiation (with or without surgery or hormonal therapy), after hormonal therapy (with or without surgery), after other treatments), time of storage before assaying (years) and batch year (2013, 2018). ^‡Number of observations used for calculations: 3329 for hsCRP; 3348 for IL-8; 3349 for IL-4; 3350 for IL-1β, IL-6, TNF-α, IL-10 and IL-13. ^§Concentrations of Inflammatory biomarkers were calculated on the log scale and exponentially transformed back for interpretation.

Figure 2.

Adjusted^† associations of plant-based Indices (per 10-point increase) with absolute changes (cm²) of body composition ^‡. hPDI, healthful plant-based diet index; PDI, overall plant-based diet index; SAT, subcutaneous adipose tissue; uPDI, unhealthful plant-based diet index; VAT, visceral adipose tissue. ^† Multiple linear regression were adjusted in separate models for (1) demographic and clinicopathological factors: age (years), race and ethnicity (American Indian/Alaska Native, Asian/Pacific Islander, Black, Hispanic, non-Hispanic White), education (high school or less, some college, college graduate, postgraduate, unknown), income (<$50 000, $50 000–$89 999, ≥$90 000, unknown), marital status (married, single, unknown), menopausal status (premenopausal, postmenopausal), stage (I, II, III, IV), ER (positive, negative, unknown), PR (positive, negative, unknown), HER2 (positive, negative, unknown) and Elixhauser comorbidity index (0, 1, 2, ≥3, unknown); and (2) lifestyle factors: total energy intake (kcal/d), BMI (kg/m²), physical activity (MET-h/week) and smoking status (never, former, current, unknown). ^‡ Number of observations used for calculations (muscle, VAT and SAT): 741.