Chemistry Reference
In-Depth Information
of oesophageal/stomach cancer (Knekt, 1993), where an overall reduction in
cancer mortality, particularly mortality from stomach and oesophageal cancer,
was observed. The efficacy of supplementation with
-tocopherol on the
prevention of certain cancers in male smokers was investigated in the Finnish
ATBC study. There was no decrease in the incidence of lung cancer among men
supplemented with synthetic
-tocopherol compared to those who were not fed
supplements. In contrast, prostate cancer incidence and mortality were reduced
by 32 and 41%, respectively, among the vitamin E-supplemented group
(Heinonen et al., 1998). Overall results of epidemiological studies relating to
vitamin E and colon cancer have been inconsistent and mixed.
Recent epidemiological experiments and mechanistic evidence suggest
that
-tocopherol may be a more potent cancer chemopreventative agent
than
-tocopherol. A nested case-control study examined the association of
-tocopherol,
-tocopherol and selenium with the incidence of prostate
cancer (Helzlsouer et al., 2000). The most striking finding was that men in
the highest quintile of plasma
-tocopherol concentration had a fivefold
reduction in the risk of prostate cancer compared with those in the lowest
quintile. Wagner et al. (2004) concluded that only the plasma level of
-tocopherol served as a biomarker of CVD and cancer. The differences in
chemical reactivity, metabolism and biological activity that may contribute to
the differences in the effects of
-tocopherol compared to
-tocopherol are
discussed by Jiang et al. (2001) and Campbell et al. (2003).
In summary, inverse associations between dietary and supplemental
vitamin E intakes and the incidence of several common chronic diseases
have been noted in many observational studies, whereas the results of studies
using blood concentration of vitamin E have been limited and inconsistent
(Sung et al., 2003; Gaziano, 2004). Randomized trials using supplemental
vitamin E have not shown substantial effects on mortality end-points (Sung
et al., 2003; Jialal and Devaraj, 2005). However, Wright et al. (2006) reported
the findings of a prospective cohort study of 29092 Finnish male smokers,
aged 50-69 years who participated in the ATBC Study. They evaluated the
prospective association between the circulating concentration of
-toco-
pherol and total and cause-specific mortality in the group. Significantly
lower total and cause-specific mortality in older male smokers were observed
as the serum
-tocopherol value increased from 9.1 mg/l (21 mmol/l) to
13-14 mg/l (
30-33 mmol/l), after which no further benefit was noted.
12.4.5.
Vitamin E in Milk
The concentration of vitamin E in animal products is usually low but
they may be significant sources of the vitamin because of their high level
of
consumption.
Different
authors
have
reported
concentrations
of
