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Mechanisms and Biomarkers (WG 4) page 48
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Chapter 4. Human Interventiuon Studies with Tomato Components
EFFECT OF TOMATO AND/OR LYCOPENE ON OXIDATIVE STRESS
Most of the literature on tomato refers to tomato and/or lycopene effects on different
biomarkers linked to oxidative stress, and involves in vitro and animal studies; human studies
are far from exhaustive. In general we have more information on lycopene than on the tomato
itself.
Intervention trials are generally carried out on small groups of subjects and mainly scheduled
to investigate bioavailability of lycopene from different tomato sources. In contrast there are
very few human studies trying to support or confirm the effect of lycopene and tomato
consumption on health.
The main biomarkers investigated are related to lipid peroxidation and DNA damage, but
limited information is available on total antioxidant capacity of plasma, protein oxidation, and
immune function. The methodologies to study such parameters generally involve ex vivo
oxidative treatments. Actually, in some cases, ex vivo supplementation is preferred to in vivo
supplementation with the disadvantage that results can only be referred to as the potential
effect of a “non-physiological” enrichment and can not be related to the role of the tomato.
Lipid peroxidation
The results are still controversial, and there are no unequivocal conclusions on the possible
protective role of tomato/lycopene against lipid oxidation. Several limitations in the methods
for the quantification of lipid damage have to be considered (e.g. TBARS as previously
reported).
It has been reported that subjects consuming a lycopene free diet had higher lipid
peroxidation than those on their habitual diet (Rao and Argawal, 1998a), and that after an
oxidative stress deriving from both the ingestion of a meal or a glucose solution and from
cigarette smoking, serum lycopene concentration decreased.
Enrichment of LDL with lycopene was demonstrated to reduce their susceptibility to metal
ion-dependent (CuSO4) or -independent (2,2-azobis, 2,4-dimethyl-valeronitril) oxidation; this
was selective of LDLs with high vitamin E content; this was selective to LDLs with high
vitamin E content. A synergistic effect was confirmed as the combination of carotenoids
together with vitamin E increased protection against LDL oxidation (Fuhrman et al, 1997). In
contrast no effect was seen by Romanchick et al. (1997) as lycopene was destroyed very