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Observational epidemiological surveys (WG 3) page 23
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1-2-3 Lycopene (Tables 11-14)
Comments on tables 11-14
All the studies (case-control, prospective, based on dietary intake or tissue concentration
assessment) showed no relationship between lycopene and various cancer sites with the
noticeable exception of the prospective Physicians Health Study which showed a decreased
OR in prostate cancer patients with a high plasma level of lycopene, significant only in
agressive tumors. This effect was found in non β-carotene supplemented subjects, although
the OR was decreased in β-carotene supplemented subjects with low lycopene plasma levels.
Because of this peculiar finding the authors remained very cautious in their conclusions and
called for more studies. The study on adipose tissue from breast cancer patients (Zhang et al.,
1997) showed a decreased risk with higher than median lycopene concentrations. This was
also shown for β-carotene (Table 16). However, this study is limited by the small sample size
(46) and by data collection in 2 one-year apart batches. One study from Japan (Nagata et al.,
1999) based on plasma lycopene concentration suggest an inverse relationship between
lycopene levels and cervical dysplasia, however the authors acknowledge the fact that low
levels of carotenoids might be a consequense and not a cause of the cervical dysplasia.
Altogether, these results are disappointing and there is no evidence that improved food
composition tables allowed to unravel a protective effect of lycopene on cancers. Because
antioxidants and especially carotenoids appeared related to cervical cancer, it might be
interesting to look at lycopene relationship with this cancer in larger and better studies than
the two reported so far (Palan et al., 1996; Kanetsky et al.,1998).
Comparison between tables 8 and 11-14
This comparison suggests that lycopene is not the micronutrient responsible for the
relationship between tomato and lung cancer.