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Observational epidemiological surveys (WG 3) page 14
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Table 6: Level of evidence of protection provided by studies on vitamin C
and cancers
cancer sites CNERNA
(France, 1996)
World Cancer Res
Fund (USA, 1997)
mouth and pharynx consistent possible no data reported
larynx consistent but limited insufficient no data reported
COMA Food and Nutrition
Policy (UK, 1998)
oesophagus consistent possible moderately consistent
lung and respiratory
tract
moderately consistent possible inconsistent
stomach consistent probable strongly consistent
colon-rectum inconsistent insufficient inconsistent
pancreas consistent possible moderately consistent but
limited
liver ND no data reported ND
breast inconsistent insufficient insufficient
ovary inconsistent insufficient no data reported
endometrium no data reported insufficient no data reported
cervix moderately consistent possible moderately consistent
prostate no data reported no relationship inconsistent
kidney ND insufficient ND
bladder ND insufficient insufficient
thyroid
ND: Not Done
ND no data reported ND
Comments on table 6
There was a high level of agreement either to show consistent reduction of risk for stomach
cancer, and, moderately consistent, for oesophagus, mouth, pharynx, larynx, pancreas, and
cervix cancers, or to acknowledge the inconsistency or insufficiency of findings on colon,
rectum and hormone-dependent cancers.
One disagreement was found for lung cancer, COMA denied the possible risk reduction
because of the few studies showing an increase in risk. However, the OR are all non
significant.
Comparison between tables 2 and 6
It appears that vitamin C can play a role in the reduction of risk of larynx, oesophagus, lung
and respiratory tract, stomach, pancreas and cervix cancers; or alternatively that vitamin C is
a marker of fruit and vegetables intake.
1-1-6 Vitamin E (Table 7)
The conclusions of the three reference books, which are summarised in this part, did not
differentiate between dietary intake and plasma levels, and are presented as such in Table 7.