Bandolier 57 highlighted the importance of homocysteine for heart disease, and the
role of dietary folate in reducing both homocysteine levels and heart disease.
Folate, especially from multivitamin use, is also implicated as a factor in reducing
risks of colon cancer [1].
Study
In 1980, 88,756 women gave detailed information on their dietary habits, including
their use of multivitamins, with regular updates over subsequent years. There was
also information available on demographics, and smoking, physical activity, aspirin
use, colonoscopy and parental history of colorectal cancer.
Up to 1994 there were 655 new cases of colorectal cancer, 442 in the colon, 143 in
the rectum and 70 at undetermined sites. The way in which these cases were
distributed according to folate intake was subjected to detailed scrutiny.
Results
High total intake of folate in 1980 was inversely related to the risk of colon
cancer (Figure 1), even after making adjustments for almost 20 possible confounding
factors. This was also the case after allowing for possible confounding factors from
other nutrients that were included in multivitamins.
When the risk was examined for multivitamin use, it became clear that the benefits
of folate supplementation only became significantly apparent for 15 years of use,
though there was a distinct trend after five years (Figure 2).
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Comment
This paper has examined the association between folate intake and colon cancer
in this large cohort of women from many different angles. It may just be wrong,
but that is unlikely. There is supporting evidence showing that high folate
intake is associated with reduced colon cancer risk from other studies.
The bottom line with homocysteine and heart disease was eat well and take a
multivitamin a day. With the potentially very large reductions in colon cancer
also on offer, although perhaps after some time, this makes even more sense as
part, with exercise, of a healthy living programme.
A particular feature of the paper is that it seeks and discusses some basic
features of carcinogenesis and how folate intake may affect this. This puts a
biological plausibility on the tale, which, with its cautious exploration of
potential limitations, makes for a gripping read uncommon in scientific papers.
Reference:
- E Giovanucci et al. Multivitamin use, folate, and colon cancer in women in
the nurses' health study. Annals of Internal Medicine 1998 129: 517-524.
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