Effect of vitamin D and sun exposure on breast cancer.
Article Type: Clinical report
Subject: Alfacalcidol (Health aspects)
Calcifediol (Health aspects)
Vitamin D (Health aspects)
Breast cancer (Diagnosis)
Breast cancer (Care and treatment)
Sun exposure (Health aspects)
Author: Murphy, Kathleen
Pub Date: 03/22/2011
Publication: Name: Australian Journal of Medical Herbalism Publisher: National Herbalists Association of Australia Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2011 National Herbalists Association of Australia ISSN: 1033-8330
Issue: Date: Spring, 2011 Source Volume: 23 Source Issue: 1
Geographic: Geographic Scope: Australia Geographic Code: 8AUST Australia
Accession Number: 254971782
Full Text: Engel P, Fagherazzi G, Mesrine S et al. 2011. Joint effects of dietary vitamin D and sun exposure on breast cancer risk: results from the French E3N cohort. Cancer Epidemiol Biomarkers Prev 20:1;187-98.

Experimental studies have shown anticarcinogenic properties of vitamin D through regulation of proliferation, differentiation and apoptosis of breast cells in vitro and in vivo. Solar ultraviolet radiation B (UVB) irradiation (280-315 nm) provides 50% to 90% of the circulating vitamin D through cutaneous conversion of 7-dehydrocholesterol, the remaining coming from the diet, especially dairy foods and fish or from dietary supplements.

The objectives of this longitudinal study were to evaluate the relationship between breast cancer (BC) risk and overall vitamin D intake from diet and UV solar exposure in the large French E3N cohort taking into account calcium intake and menopausal status.

E3N is a prospective cohort initiated in 1990 that includes 98 995 French women born between 1925 and 1950. Participants completed biennial self administered questionnaires sent from 1990 to 2008 on medical and gynacological history, menopausal status and a variety of lifestyle characteristics. Occurrence of cancer was self reported in each questionnaire. The pathology report used to confirm the diagnosis of invasive BC (the primary outcome) was obtained for 93% of declared BC cases.

A validated 208 item diet history questionnaire assessed the previous year's usual diet. From this researchers estimated the average daily vitamin D, calcium and energy intakes. Information on vitamin D and calcium supplement use was extracted from questions on treatment/prevention of osteoporosis and on dietary supplementation.

Data on region of residence was assessed for all participants at baseline and linked to a database containing mean daily ultraviolet radiations doses (UVRd in kJ/m2/ day). Information on region of residence was assessed in 1990 (first questionnaire), at baseline (diet questionnaire) and at the end of follow up. In addition birth place, data on skin complexion, recreational physical activity and usual sunburn resistance were requested at inclusion.

A total of 2 871 incident primary invasive BC were diagnosed during the 10 year follow up (618 were premenopausal and 2 253 postmenopausal) in the 67 721 women included in the analysis. Vitamin D intake from either diet or supplements was not associated with overall, pre or postmenopausal BC risk. Living in the regions with the highest UVRd (>2.7 kJ/m2/day) was associated with a statistically significant decreased BC risk compared with women with the lowest UVRd (HR = 0.91, 95% CI: 0.82-0.99, P for trend across quartiles = 0.06), especially in postmenopausal women (HR = 0.92, 95% CI: 0.82-0.98; P for trend = 0.05).

Researchers observed a significant interaction between UVRd and dietary vitamin D intake in post (P !4 0.02) but not in premenopausal women (P=0.4). BC risk was significantly decreased in women with both high UV exposure and the highest dietary (>113 IU/day) or supplemental vitamin D intakes. The association was restricted to postmenopausal women (corresponding HRs = 0.68, 95% CI: 0.54-0.85 and 0.57, 95% CI: 0.36-0.90, respectively).

A limitation to this study is that it only used a single dietary assessment and could subsequently not estimate long term effects of vitamin D dietary intake.Actual sun exposure was not quantified but UVR doses were estimated based on previous studies. Further investigations are warranted to improve assessment of UVR exposure and its correlation with the vitamin D status.

The results suggest that a threshold of vitamin D exposure from both sun and diet is required to prevent BC and this threshold is particularly difficult to reach in postmenopausal women in latitudes where quality of sunlight is too poor for adequate vitamin D production.

Kathleen Murphy mnhaa

murphykath@gmail.com
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