The randomised, placebo-controlled, double-blinded crossover study in 71 subjects showed that supplements of lycopene may increase levels of proteins that bind to insulin-like growth factor (IGF), linked with cancer risk.
The study, published late last year in the American Journal of Clinical Nutrition , extends our understanding of the potential anti-cancer benefits of lycopene, most notably linked to a lower risk of prostate cancer.
"This is the first study known to show that lycopene supplementation may increase circulating IGF-binding protein(BP)-1 and IGFBP-2 concentrations, thereby potentially decreasing IGF-I bioavailability," said lead author Alina Vrieling of the Netherlands Cancer Institute in Amsterdam.
"Thus, it may provide a means of ultimately reducing colorectal cancer risk, and potentially the risks of other major cancers such as prostate and pre-menopausal breast cancer."
Vrieling and co-workers recruited 40 men and 31 women with a family history of colorectal cancer and/or a personal history of colorectal adenoma, and randomly assigned them to receive either a daily tomato lycopene supplement (30 mg per day, LycoRed) or placebo for eight weeks.
Blood samples were taken to measure levels of IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3.
"Serum concentrations of IGF-I and -II which are associated with increased prostate, pre-menopausal breast, and colorectal cancer risk," explained the researchers.
Vrieling and co-workers report that supplementation with lycopene was associated with a 21.7 per cent increase in IGFBP-1 concentrations in women, compared to placebo.
IGFBP-2 concentrations increased in both men and women after lycopene supplementation by 8.2 and 7.8 per cent, compared to placebo, they added.
The researchers also noted large variations between individuals' IGFBP-1 and IGFBP-2 concentrations.
On the other hand, no significant changes between lycopene and placebo groups were observed for Total IGF-I, IGF-II, and IGFBP-3 concentrations.
Commenting on the role results of the study, Vrieling stated "This research is interesting, and we hope to see the results confirmed in larger randomised intervention studies."
There are 363,000 new cases of colorectal cancer every year in Europe, with an estimated 945,000 globally.
There are about 492,000 deaths from the cancer each year.
Only about five per cent of colorectal adenomas are thought to become malignant, and this process could take between five and ten years.
Beyond colorectal cancer Epidemiological evidence has suggested that tomato-based foods can protect men from prostate cancer.
One study found that men eating four to five tomato based-dishes per week were 25 per cent less likely to develop prostate cancer compared to men eating tomatoes only rarely.
Such findings are boosting the lycopene market, with growth rates forecast at over 100 per cent by Frost and Sullivan, albeit from a low base of around €27m ($34m) in 2003.
Recently, researchers taking part in the Europe-wide European Prospective Investigation into Cancer and Nutrition (EPIC) reported that increased blood levels of lycopene may reduce the risk of advanced prostate cancer by 60 per cent.
"To our knowledge, this is the largest prospective study to date of plasma carotenoids, retinol, tocopherols, and prostate cancer risk," wrote lead author Timothy Key from Cancer Research UK in the American Journal of Clinical Nutrition (Vol. 86, pp.
672-681).
Source: American Journal of Clinical Nutrition November 2007, Volume 86, Pages 1456-1462 "Lycopene supplementation elevates circulating insulin-like growth factor-binding protein-1
and
-2 concentrations in persons at greater risk of colorectal cancer" Authors: A. Vrieling, D.W. Voskuil, J.M. Bonfrer, C.M. Korse, J. van Doorn, A. Cats, A.C. Depla, R. Timmer, B.J. Witteman, F.E. van Leeuwen, L.J. van't Veer, M.A. Rookus, E. Kampman