world cancer report - iarc

dietary-related cancers considered attributable
to food additives is very low [13].
Micronutrients
Research on vitamins and cancer in
humans has focused mainly on
carotenoids and vitamin A (retinol), vitamin
E, vitamin C and some of the group of
B vitamins (folic acid, B 6). The biological
basis of the interest in these vitamins is
their involvement in either of two metabolic
mechanisms commonly called the
antioxidant effect (carotenoids, vitamins C
and E) and methyl donation (folic acid, B 6)
(Chemoprevention, p151).
case-control studies based on dietary
questionnaires and several small prospective
cohort studies based on blood measurements
have shown quite consistently
that individuals with lower carotenoid levels
have increased lung cancer risk. Less
consistent and weaker protective effects
of carotenoids have also been reported for
cancers of the oesophagus, stomach,
colorectum, breast and cervix. Low
dietary intake of vitamin C has been found
to be associated with increased risk of
cancers of the stomach, mouth, pharynx,
oesophagus and, less consistently, with
cancers of the lung, pancreas and cervix.
Although results on vitamin E and cancer
are less strong and consistent than those
on carotenoids and vitamin C, several
PATTERNS OF RED MEAT CONSUMPTION
A
< 11.1
< 21.1 < 31.2
g/day
< 41.3
studies have suggested that low vitamin E
intake is related to increased risk of cancers
of the lung, cervix and colorectum.
Studies to investigate the effect of dietary
supplementation with vitamins on cancer
risk have had varying results (Chemoprevention,
p151). Two large studies, ATBC
and CARET [14], observed increases in
lung cancer incidence of 18% and 28%
respectively in the group receiving βcarotene
(β-carotene plus vitamin A in
CARET). In the ATBC study, the group
receiving a vitamin E supplement had a
34% reduction in prostate cancer incidence,
but deaths from cerebrovascular
accidents doubled and there was no
decrease in total mortality.
There is rising interest in the possible cancer-preventive
effect of folic acid; some
prospective studies have shown that high
dietary intakes and higher blood levels may
be associated with reduced risk of cancers
and adenomatous polyps of the colorectum.
Folates and vitamin B 6 are involved in
the synthesis of methionine and choline as
methyl donors. Folate deficiency leads to
an accumulation of homocysteine. High
homocysteine levels have recently been
found to be strongly associated with death
from myocardial infarction, total mortality
and colon cancer risk [15].
Epidemiological studies conducted in
populations with a high incidence of
< 51.3
Relative risk
Fish
Poultry
Processed meat
Red meat
Meat
INCIDENCE OF COLORECTAL CANCER IN MEN
0.6 0.8 1.0 1.2 1.4 1.6 1.8
Cohort study
All studies
case-control study
Fig. 2.57 Influence of the consumption of fish and
different types of meat on the relative risk of
developing colorectal cancer [7].
oesophageal cancer in China found that
zinc deficiency was common in these populations.
Some experimental studies also
suggest that selenium deficiency may
increase cancer risk [16]. Several epidemiological
studies have examined the
association between cancer risk and deficiencies
of one of these minerals, with
very variable results.
< 5.0 < 9.4 < 13.8 < 31.0 < 60.3
Age-standardized rate/100,000 population
Fig. 2.58 The global levels of (A) red meat consumption (beef, lamb and pork) and its relationship to (B) the incidence of colorectal cancer. The biological basis
of the correlation between these two variables is complex and not yet fully understood.
B
Diet and nutrition
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