world cancer report - iarc

Fig. 2.54 The age-adjusted mortality rate for gastric cancer increases with increasing salt consumption,
as measured by 24-hour urine sodium excretion, in selected regions of Japan.
S. Tsugane et al. (1991) Cancer Causes Control, 2:165-8.
a protective effect of animal protein (and
meat) while some studies on colorectal
cancer found an increased risk for animal
protein (and meat).
Results on carbohydrates are difficult to
interpret because of inconsistencies in the
way different food composition tables
subdivide total carbohydrates into subfractions
that have very different physiological
and metabolic effects and which
may affect carcinogenesis in opposite
ways. The only pattern that seems to
emerge so far is that consumption of simple
sugars (mono- and disaccharides) may
be associated with increased colorectal
cancer risk, while consumption of complex
polysaccharides, non-starch polysaccharides
and/or fibre (partially overlapping
categories based on different chemical
and physiological definitions) is associated
with lower cancer risk. Other less
consistent findings suggest that a diet
excessively rich in starchy foods (mainly
beans, flour products or simple sugars)
but also poor in fruit and vegetables, may
be associated with increased gastric cancer
risk.
The hypothesis that high fat intake is a
major cancer risk factor of the Westernstyle
diet has been at the centre of most
64 The causes of cancer
epidemiological and laboratory experimental
studies. The results are, however,
far from clear and definitive. The positive
association with breast cancer risk suggested
by international correlation studies
and supported by most case-control studies
was not found in the majority of the
prospective cohort studies conducted so
far. Very few studies have investigated the
effect of the balance between different
types of fats, specifically as containing
poly-unsaturated, mono-unsaturated and
saturated fatty acids, on cancer risk in
humans. The only moderately consistent
result seems to be the positive association
between consumption of fats of animal
origin (except for fish) and risk of
colorectal cancer. Additionally, olive oil in
the context of the Mediterranean dietary
tradition is associated with a reduced risk
of cancer [10].
Food additives
Food additives are chemicals added to
food for the purpose of preservation or to
enhance flavour, texture or colour. Less
than comprehensive toxicological data are
available for most additives, although
some have been tested for mutagenic or
carcinogenic activity. In in vitro assay sys-
Fig. 2.55 Consumption of salted fish (such as this
salted cod) is associated with an increased risk of
stomach cancer.
tems, some additives, such as dietary phenolics,
have both mutagenic and antimutagenic
effects [11]. In the past, some
chemicals were employed as food additives
before their carcinogenicity in animals
was discovered, e.g. the colouring
agent “butter yellow” (dimethylaminoazobenzene)
and, in Japan, the preservative
AF2 (2-(2-furyl)-3-(5-nitro-2-furyl)
acrylamide). Saccharin and its salts have
been used as sweeteners for nearly a century.
Although some animal bioassays
have revealed an increased incidence of
urinary bladder cancer, there is inadequate
evidence for carcinogenicity of saccharin
in humans [12]. The proportion of
Fig. 2.56 Saccharin with a warning label recognizing
a possible role in cancer causation.