It is known that defiency in dietary folate may predispose individuals
to cancer, as a deficiency disrupts DNA synthesis and repair.Heavy
intake of alcohol is also associated with elevated risks of breast
cancer, but few studies have examined the relationship between
folates and alcohol.
An important paper by TE Rohan , Meera et al published in the
Journal of the National Cancer Institute has found that the combination
of high folate intake and moderate consumption of alcohol shows
a marked reduction in incidence of breast cancer.
The researchers examined the association between dietary folate
intake and breast cancer risk and its modifications by methionine
and alcohol intake in a cohort study of 56,837 women in the Canadian
National Breast Screening study. The participants completed a
self administered food frequency questionnaire covering 86 food
items, including alcohol. The values for folate intake were from
dietary sources alone, since data on the content of vitamin supplements
was not available. Major sources were liver, green leafy vegetables
and whole grain cereals. 1469 women were diagnosed with invasive
carcinoma of the breast during the follow up between 1980 and
1993. A control group of 5382 women was also set up at random
from the 56,837 participants.
Overall, as well as in post menopausal women alone, there was
no association between dietary folate intake alone and breast
cancer risk. Risk varied little in association with folate intake
among women in the lowest 80% of the distribution of alcohol consumption
( i.e. less than one 14g unit a day) but there were marked reductions
in risk associated with folate intake among those consuming more
than 14g of alcohol a day, rising again at higher levels of alcohol
intake.The pattern was more pronounced in post menopausal women.
The study findings were similar after adjustment for years of
education, use of oral contraceptives, weight and cigarettes.
Participants using vitamin supplements were also excluded as well
as subjects with a history of non malignant breast disease or
other cancers. The authors conclude: ' Our results, although possibly
chance findings, suggest that dietary folate consumption might
be associated with reduced risk of breast cancer at relatively
high levels of alcohol consumption, particularly in post menopausal
women. Zhang et al observed a similar phenomenon in association
with total folate intake (dietary plus supplement) in both post
and pre menopausal women. Other epidemiological studies of folate
and breast cancer have not examined risk by levels of alcohol.....our
findings suggest that the adverse effects of alcohol on breast
cancer risk might be ameliorated by adequate intake of folate
from dietary sources alone'
To read the full paper and view a full list of references, see
Journal of the National Cancer Institute, Vol 92, No3 February
2 2000 pages 266-269