Vitamin D intake, month the mammogram was taken and mammographic density in Norwegian women aged 50-69.

Merete Ellingjord-Dale,Elisabeth Couto,Marianne Skov Markussen,Isabel Dos-Santos-Silva,Giske Ursin,Solveig Hofvind,Tom Grotmol,Linda Vos,Samera Qureshi,Amrit Kaur Sakhi,Olga Y Gorlova

doi:10.1371/journal.pone.0123754

Merete Ellingjord-Dale, Elisabeth Couto + Show 9 more

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https://doi.org/10.1371/journal.pone.0123754

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Abstract

BackgroundThe role of vitamin D in breast cancer etiology is unclear. There is some, but inconsistent, evidence that vitamin D is associated with both breast cancer risk and mammographic density (MD). We evaluated the associations of MD with month the mammogram was taken, and with vitamin D intake, in a population of women from Norway—a country with limited sunlight exposure for a large part of the year.Methods3114 women aged 50–69, who participated in the Norwegian Breast Cancer Screening Program (NBCSP) in 2004 or 2006/07, completed risk factor and food frequency (FFQ) questionnaires. Dietary and total (dietary plus supplements) vitamin D, calcium and energy intakes were estimated by the FFQ. Month when the mammogram was taken was recorded on the mammogram. Percent MD was assessed using a computer assisted method (Madena, University of Southern California) after digitization of the films. Linear regression models were used to investigate percent MD associations with month the mammogram was taken, and vitamin D and calcium intakes, adjusting for age, body mass index (BMI), study year, estrogen and progestin therapy (EPT), education, parity, calcium intakes and energy intakes.ResultsThere was no statistical significant association between the month the mammogram was taken and percent MD. Overall, there was no association between percent MD and quartiles of total or dietary vitamin D intakes, or of calcium intake. However, analysis restricted to women aged <55 years revealed a suggestive inverse association between total vitamin D intake and percent MD (p for trend = 0.03).ConclusionOverall, we found no strong evidence that month the mammogram was taken was associated with percent MD. We found no inverse association between vitamin D intake and percent MD overall, but observed a suggestive inverse association between dietary vitamin D and MD for women less than 55 years old.

Highlights

Almost eight decades ago, Peller et al suggested that sunlight exposure may lower breast cancer risk [1]
There was no association between percent mammographic density (MD) and quartiles of total or dietary vitamin D intakes, or of calcium intake
We found no strong evidence that month the mammogram was taken was associated with percent MD

Summary

Introduction

Peller et al suggested that sunlight exposure may lower breast cancer risk [1]. Several case-control studies have reported a significant association between higher vitamin D intake from both diet and supplements and lower breast cancer risk in premenopausal women only [5,6,7,8]. The Women’s Health Initiative found no protection of vitamin D and calcium supplements on breast cancer risk, neither during the intervention phase [10] nor 5 years after the invention was stopped [11]. There is some, but inconsistent, evidence that vitamin D is associated with both breast cancer risk and mammographic density (MD). We evaluated the associations of MD with month the mammogram was taken, and with vitamin D intake, in a population of women from Norway—a country with limited sunlight exposure for a large part of the year.

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Conclusion