Discussion
Findings from this meta-analysis suggested that the intake of
processed meat might increase the risk for glioma. Most of the
data on the issue come from the United States; thus it is obvious
that the RR estimate for the United States reflects that for overall
studies combined. We cannot combine the results for Europe,
Australia, and Israel because of limited data. Furthermore, only
three studies were conducted for red meat, and no association
was found between red meat consumption and glioma risk.
N-nitroso compounds are broadly acting and potent carcinogens
in animal models [35,36]. N-nitroso compounds can be
present in food treated with sodium nitrite or can form endogenously
if the nitrites react with secondary amines or amides
[35]. The endogenous formation of N-nitroso compounds in the
stomach is complex because it is influenced by various physiologic
parameters, including gastric pH, the presence of bacteria,
and antioxidants [37]. N-nitroso compounds have been detected
in brain tissue and can cross the blood–brain barrier [38]. Processed
and cured meat intakes have been used as markers of