I livelli circolanti di carotenoidi correlano con la riduzione del rischio di tumore mammario nel Nurses' Health Study

Eliassen AH, Liao X, Rosner B, Tamimi RM, Tworoger SS, Hankinson SE.
Am J Clin Nutr. 2015 Apr 15. pii: ajcn105080. [Epub ahead of print]

30-04-2015

L’alimentazione è un fattore cruciale di riduzione del rischio di malattie croniche e invalidanti, ma anche di tumore. I due Nurses’ Health Study, con le loro osservazioni ventennali, permettono di valutare anche il rapporto tra alimentazione e rischio di malattia. In questa analisi, emerge con chiarezza il ruolo protettivo che i carotenoidi (alfa e beta carotene, beta-criptoxantina, luteina e zeaxantina e licopene) svolgono nei confronti del rischio di tumore alla mammella. Misurando in tempi diversi nel sangue i livelli di carotenoidi, sia individuali e sia totali, si è infatti evidenziata l'associazione tra carotenoidi totali, alfa e beta-carotene (e in misura minore licopene), dosati anche  più di 10 anni prima della diagnosi, e la riduzione del rischio di tumore mammario, che è risultato diminuito del 18-28% per le donne che presentavano i livelli più elevati (e che quindi assumevano più carotenoidi con la dieta), ancor più se normopeso. La riduzione del rischio era particolarmente marcata per le forme di carcinoma più  aggressive.

Plasma carotenoids and risk of breast cancer over 20 y of follow-up.

BACKGROUND: Increasing evidence suggests that carotenoids, which are micronutrients in fruit and vegetables, reduce breast cancer risk. Whether carotenoids are important early or late in carcinogenesis is unclear, and limited analyses have been conducted by breast tumor subtypes.
OBJECTIVES: We sought to examine issues of the timing of carotenoid exposure as well as associations by breast tumor subtypes.
DESIGN: We conducted a nested case-control study of plasma carotenoids measured by using reverse-phase high-performance liquid chromatography and breast cancer risk in the Nurses' Health Study. In 1989-1990, 32,826 women donated blood samples; in 2000-2002, 18,743 of these women contributed a second blood sample. Between the first blood collection and June 2010, 2188 breast cancer cases were diagnosed (579 cases were diagnosed after the second collection) and matched with control subjects. RRs and 95% CIs were calculated by using conditional logistic regression adjusted for several breast cancer risk factors.
RESULTS: Higher concentrations of α-carotene, β-carotene, lycopene, and total carotenoids were associated with 18-28% statistically significant lower risks of breast cancer (e.g., β-carotene top compared with bottom quintile RR: 0.72; 95% CI: 0.59, 0.88; P-trend < 0.001). Associations were apparent for total carotenoids measured ≥10 y before diagnosis (top compared with bottom quintile RR: 0.69; 95% CI: 0.50, 0.95; P-trend = 0.01) as well as those <10 y before diagnosis (RR: 0.79; 95% CI: 0.64, 0.98; P-trend = 0.04, P-interaction = 0.11). Carotenoid concentrations were strongly inversely associated with breast cancer recurrence and death (e.g., β-carotene top compared with bottom quintile RR: 0.32; 95% CI: 0.21, 0.51; P-trend < 0.001) compared with not recurrent and not lethal disease (P-heterogeneity < 0.001).
CONCLUSION: In this large prospective analysis with 20 y of follow-up, women with high plasma carotenoids were at reduced breast cancer risk particularly for more aggressive and ultimately fatal disease.

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