Medicinal Plants Classification Biosynthesis and ... - Index of

Biological Effects of -Carotene
diagnosed between August 1980 and July 1984 in three western New York counties, while
controls were selected from the general population of these same counties. Usual diet was
estimated by detailed interviews using a modified food frequency method. Case-control
comparisons were made for dietary fat, protein, fiber, calories, cholesterol, and vitamins A, C,
and E according to quartiles of intake, adjusting for age and pack-years of cigarettes by
multiple logistic regression. Risk was lower for males in the lowest quartile of total dietary fat
intake compared with those in the highest quartile, although the overall trend in the
association with dietary fat was not statistically significant. Likewise, there was a weak, but
not statistically significant, direct association between dietary cholesterol and lung cancer in
men. The intake of carotene from fruits and vegetables was much more strongly associated
with reduced cancer risk. For males, the relative risks by quartiles was considerably weaker,
and was not statistically significant. These findings are generally in agreement with those of
several previous studies. The risk reduction associated with vitamin A from fruits and
vegetables (carotene) was most evident for males, for those with squamous cell cancers, for
light or ex-smokers, and for those over 60 years of age (Byers et al., 1987).
An inverse association between β-carotene intake and risk of neoplasms has been
described largely in observational studies, thus leading researchers to design many
intervention studies with this antioxidant (Hercberg et al., 2004). However, its safety is
debated (Greenwald, 2003), as some intervention studies have suggested a positive
association of high doses of supplemental β-carotene, especially in smokers, with lung cancer
(Omenn et al., 1996; Albanes et al., 1996) and with digestive cancers, during the trial or the
post-trial follow-up (Malila et al., 2002). A meta-analysis of intervention studies on digestive
tract cancers suggested a direct association between cancer incidence and intake of βcarotene
alone or combined with retinol or tocopherol (Bjelakovic et al., 2004). In an
intervention study of patients with colorectal adenomas, a precancerous lesion for colorectal
cancer, an inverse association between adenoma recurrence and β-carotene intake was
observed in non smokers, but a direct association was observed in those smokers who drank
at least one alcoholic drink per day (Baron et al., 2003). In contrast, a pooled analysis of
seven cohorts (Mannisto et al., 2004) and two intervention studies (Lee et al., 1999;
Hennekens et al., 1996) did not show a statistically significant interaction between β-carotene
and smoking with cancer incidence.
A potential interaction between β-carotene intake and smoking on the risk of tobaccorelated
cancers was investigated in 59,910 women participating in the French Etude
Epidemiologique de Femmes de la Mutuelle Generale de I'Education Nationale. After a
median follow-up period of 7.4 years, 700 women had developed cancers known to be
associated with smoking (e.g., lung, head, and neck, urinary tract, digestive tract, cervix,
thyroid, and ovary). Among women who had never smoked, there was a significant inverse
association between β-carotene intake from both diet and supplements and the risk of all
smoking-related cancers. Supplement users had a 56% lower risk of developing such cancers,
compared with women in the lowest tertile of β-carotene intake. In contrast, among women
who had ever smoked (including current and former smokers), increasing β-carotene intake
was associated with an increase in the incidence of smoking-related cancers. Smokers who
took β-carotene supplements had more than twice the risk of such cancers as did women in
the lowest tertile of β-carotene intake (hazard ratio = 2.14; 95%) (Touvier, 2005). The results
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