Vitamin D again linked to breast cancer protection

By Stephen Daniells

http://www.foodnavigator-usa.com/Science-Nutrition/Vitamin-D-again-linked-to-breast-cancer-protection

26-Sep-2008 -
Increased intake of vitamin D from the diet and from sunlight may reduce the
risk fo breast cancer by over 20 per cent, says a new study.

The potential protective effects of the vitamin were not limited by the
hormone receptor status of the tumours, according to research published
online in the American Journal of Epidemiology.

"This study suggests that vitamin D is associated with a reduced risk of
breast cancer regardless of [oestrogen-receptor (ER) positive and
progesterone-receptor (PR)] status of the tumour," wrote lead author
Kristina Blackmore from Mount Sinai Hospital in Toronto.

Over one million women worldwide are diagnosed with breast cancer every
year, with the highest incidences in the US and the Netherlands. China has
the lowest incidence and mortality rate of the disease.

Hormone-sensitive oestrogen-receptor (ER) positive and progesterone-receptor
(PR) positive tumours are said to be the most common type diagnosed among
breast cancer patients in the US. These tumours are stimulated to grow by
the female hormones oestrogen and progesterone.

Study details

"Few epidemiologic studies have considered the association between vitamin D
and hormone-receptor-defined breast cancer," wrote Blackmore.

In order to start filling this knowledge gap, the Canadian researchers
analysed the vitamin D intakes of 759 women with breast cancer, and compared
this to the vitamin D intakes of 1,135 healthy controls.

Increased intakes of the vitamin were associated with a 24 per cent
reduction in the risk of developing ER+ and PR+ tumours, said the
researchers. Moreover, increased intakes were also associated with 26 and 21
per cent reductions in the risk of receptor-negative (ER-/PR-) and mixed
receptor (ER+/PR-) tumours. However, these last two associations were not
significant, said the researchers.

"Future studies with a larger number of receptor-negative and mixed tumours
are required," they concluded.

D and the big C

The link between vitamin D intake and protection from cancer dates from the
1940s when Frank Apperly demonstrated a link between latitude and deaths
from cancer, and suggested that sunlight gave "a relative cancer immunity".

Vitamin D refers to two biologically inactive precursors - D3, also known as
cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2
precursors are hydroxylated in the liver and kidneys to form 25-
hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and
1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is
tightly controlled by the body.

There is growing evidence that 1,25(OH)2D has anticancer effects, but the
discovery that non-kidney cells can also hydroxylate 25(OH)D had profound
implications, implying that higher 25(OH)D levels could protect against
cancer in the local sites.

Source: American Journal of Epidemiology
Published online ahead of print, doi:10.1093/aje/kwn198
"Vitamin D From Dietary Intake and Sunlight Exposure and the Risk of
Hormone-Receptor-Defined Breast Cancer"
Authors: K.M. Blackmore, M. Lesosky, H. Barnett, J.M. Raboud, R. Vieth, J.A.
Knight