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Observational epidemiological surveys (WG 3) page 27
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1-2-4 Carotenoids (Table 15-17)
Comments on Table 15-17
The recent case-control and prospective studies totally agreed with the previous results on the
risk reduction of stomach and lung cancers confered by fruit and vegetables intake (to which
we can add the effect on mouth and pharynx cancer Bosetti et al., 2000). A possible
interaction (or confusion) with vitamin C should be noted. For colon-rectum, the new results
were inconsistent as stated in the reference books with only one case-control study based on
dietary intake from Italy showing a significant risk reduction. Ten new studies were reported
for breast cancers: three case-control studies conducted in Mediterranean countries showed
significant protection, one in Uruguay showed a protection by α-carotene, whereas the
prospective studies conducted in the USA and Netherlands were non significant, although the
level of consumption appears similar between Italy and USA. For studies based on tissue
concentration, only a small case-control study suggested that β-carotene concentration was
lower in breast cancer patient’s fat than in fat from normal control. A large transversal
multicentric study (Germany, Netherlands, Switzerland, Northern Ireland and Spain) and a
prospective one showed no relationship between breast cancer and β-carotene tissue
concentration (van’t Veer et al., 1996). Thus, positive results solely come from Mediterranean
countries Italy and Greece. Reports of a protective effect of β-carotene for endometrium and
thyroid cancers also came from Italy. Several questions arise from this observation:
A methodological bias is not likely since methods were not the same in Greece and
Italy, and not the same for breast, endometrium and thyroid cancers.
Are these results an indication of a protective common factor in the Mediterranean
diet, which is not necessarily carotenoids, but present together with carotenoids in the food
habits?
Comparison between tables 8, 9 and 15-18
The main observation of this comparison is that β-carotene can in part mediate the protective
effect of tomatoes and other fruit and vegetables for lung and stomach cancers. However a
synergic or additive interaction with other compounds, among them vitamin C is strongly
suggested.