Vitamins cause cancer?

[Guest guest]

Hi All,

The first (1) below that it seems to be in a journal that

our library just terminated a subscription in, suggests

that too much of a good thing like vitamins is bad. Vitamin

B12 being such a big factor in prostate cancer makes me wonder

about total meat consumption. I wonder if red meat over-

consumption may be the unexamined explaining factor?

The study being a prospective study is a plus.

However, there is a second paper (2) that seems to say that the

region of the

colo-rectum that is examined and the type of meat is important.

If it were only the vitamin B12, fish and chicken should also have

been risks. Therefore, what might it be about red meats that is so

particular?

(1) Int J Cancer. 2004 Oct 21; [Epub ahead of print]

Plasma folate, vitamin B12, and homocysteine and prostate cancer

risk: A

prospective study.

Hultdin J, Van Guelpen B, Bergh A, Hallmans G, Stattin P.

... maintenance of adequate folate status tending to show a

protective effect. Aberrant methylation, primarily hypermethylation

of certain

genes including tumor suppressors, has been implicated in prostate

cancer

development. Folate, vitamin B12 and homocysteine are essential for

methyl group

metabolism and thus also for DNA methylation. ... 254 case subjects

and

514 matched control subjects. Increasing plasma levels of folate and

vitamin B12

were statistically significantly associated with increased prostate

cancer risk,

with an odds ratio of 1.60 (95% CI = 1.03-2.49; p(trend) = 0.02) for

folate and

2.63 (95% CI = 1.61-4.29; p(trend) < 0.001) for vitamin B12 for

highest vs.

lowest quartile. Increasing plasma homocysteine levels were

associated with a

reduced risk of borderline significance (OR = 0.67; 95% CI = 0.43-

1.04; p(trend)

= 0.08). After adjustment for the other 2 plasma variables, body mass

index and

smoking, a statistically significant increased risk remained only for

vitamin

B12 (OR = 2.96; 95% CI = 1.58-5.55; p(trend) = 0.001). Adjusted OR

for folate

and homocysteine were 1.30 (95% CI = 0.74-2.24; p(trend) = 0.17) and

0.91 (95%

CI = 0.51-1.58; p(trend) = 0.60), respectively. Our results suggest

that factors

contributing to folate status are not protective against prostate

cancer. On the

contrary, vitamin B12, associated with an up to 3-fold increase in

risk, and

possibly also folate, may even stimulate prostate cancer development.

These

findings are novel and should be explored further in future studies.

PMID: 15499634 [PubMed - as supplied by publisher]

(2)Int J Cancer. 2004 Oct 21; [Epub ahead of print]

Red meat consumption and risk of cancers of the proximal colon,

distal colon and

rectum: The Swedish Mammography Cohort.

Larsson SC, Rafter J, Holmberg L, Bergkvist L, Wolk A.

Although there is considerable evidence that high consumption of

red meat may

increase the risk of colorectal cancer, data by subsite within the

colon are

sparse. The objective of our study to prospectively examine whether

the

association of red meat consumption with cancer risk varies by

subsite within

the large bowel. We analyzed data from the Swedish Mammography Cohort

of 61,433

women aged 40-75 years and free from diagnosed cancer at baseline in

1987-1990.

Diet was assessed at baseline using a self-administered food-frequency

questionnaire. Over a mean follow-up of 13.9 years, we identified 234

proximal

colon cancers, 155 distal colon cancers and 230 rectal cancers. We

observed a

significant positive association between red meat consumption and

risk of distal

colon cancer (p for trend = 0.001) but not of cancers of the proximal

colon (p

for trend = 0.95) or rectum (p for trend = 0.32). The multivariate

rate ratio

for women who consumed 94 or more g/day of red meat compared to those

who

consumed less than 50 g/day was 2.22 (95% confidence interval [CI]

1.34-3.68)

for distal colon, 1.03 (95% CI 0.67-1.60) for proximal colon and 1.28

(95% CI

0.83-1.98) for rectum. Although there was no association between

consumption of

fish and risk of cancer at any subsite, poultry consumption was

weakly inversely

related to risk of total colorectal cancer (p for trend = 0.04).

These findings

suggest that high consumption of red meat may substantially increase

the risk of

distal colon cancer. ...

PMID: 15499619 [PubMed - as supplied by publisher]

Cheers, Alan Pater