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Observational epidemiological surveys (WG 3) page 17
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studies and 17 prospective studies, most of them based on dietary intake, one study was based
on blood concentration and three studies were based on tissue concentrations. We excluded
the study by Harrisson et al., (1997) a case-control study on gastric adenocarcinomas with
only 91 cases subdivided in intestinal (60) and diffuse type (31). This study concluded to the
protective effect of fruit, and, only vitamin C for the diffuse type after energy adjustment. We
also excluded the study by Huang et al. (2000) because the dietary assessment was scanty
(frequent/less frequent). The results showed a significant but moderate risk reduction of
gastric cancer risk by fruit and fresh vegetables. The study by Vlajinac et al. (1997) with 101
cases with prostate cancer was excluded because the adjustment for potential confounders
appeared unclear and insufficient. This study concluded on the protective effect of vitamin E.
One study (Baldwin et al., 1997) quoted in the review by Giovanucci (1999) was not used
because it was referenced as an abstract and was not yet published. Two case-control studies
reported on cervical dysplasia. One reported in 1996, (Palan et al., 1996) was based on
plasma concentration of lycopene. This study was not considered in the reference books
because the samples were small and there is no estimation of the relative risk but the
calculation of an inverse trend between the plasma lycopene levels of normal subjects (82),
subjects with increasing severity of cervical intraepithelial neoplasia (52 grade 1; 37 grade 2
and 25 grade 3) and subjects with actual cervical cancer (14). The trend was significant (P=
0.0023) from 530 ± 24.5 µg/liter to 33.7 ± 12.0 µg/liter. However the limitations of this study
precluded any conclusion. Kanetsky et al. (1998) reported also on lycopene blood levels and
intake in relation to cervical dysplasia. It was excluded because of the small number of cases
(32) and the non-significance of the results after adjustment. We excluded the study by
Farrow et al. (1998) on naso-pharynx carcinoma because we were more interested in
epithelial cancers, and the OR were only borderline significant for β-carotene. We made
exception for the case-control studies by Negri et al., (1996-b) and d’Avanzo et al. (1997) in
which the dietary questionnaire was limited to 29 food groups, because they report on less
frequent cancers, i.e. endometrium and thyroid cancers; and for the study by Zhang et al.
(1997) which reports on adipous breast tissue from 46 cases only because of the well known
quality of the authors. Also, the study by Galanis et al. (1998) on gastric cancer using a short
food freqency questionnaire of 13 food groups was retained because it is a prospective study.
We present tables as summaries of these recent results on fruit and vegetables, carotenoids,
vitamin C and vitamin E.