and cancer)
and neurological manifetations
(> 20 cigarettes / day => 15% likelihood of lung
carcinoma
in entire life). Nicotine acts as a cocarcinogen. Cells on the spurs between
airways build up inhaled carcinogens to concentrations at least 100 times
higher than elsewhere in the lung : some safe limits for pollutants could
be underestimates. Some particles are washed away by mucus and coughing;
others - such as tobacco smoke - are not, hence the dry, hacking cough
of a smoker. High-tar cigarettes leave deposits high up in the lungs, lower-tar
ones stain deeper in the lungs because smokers suck on them harder.
and scrotal nonmelanoma
skin cancers
in chimney-sweeps due to gravity deposition and poor hygiene
,
E250
(NaNO2),
E252
(KNO2)).
Addition of nitrite leads to an attractive colour in meat products, protects
against fat oxidation and, in particular, inhibits outgrowth of Clostridium
spp..
Nitrates and nitrites have long been used as food preservatives/additives.
Preserved meats such as ham, lunch meats, bacon, and hot dogs are high
in nitrates and nitrites and should never be pureed and added to baby food
for young infants. Further, foods containing these products should not
be saved in the refrigerator for older infants. Processed meats, with the
exception of dry sausage (salami, pepperoni, etc.) and dry-cured hams,
use only sodium nitrite and not nitrates. The usage level of sodium nitrite
is limited in the USA in all meat products to 156 parts per million (ppm)
sodium nitrite based on meat weight. It has occasionally been mistaken
for salt or sugar)
and vitamin Ewhich
are known to inhibit the formation of N-nitrosamine. the risk of
GC decreased with high consumption of fresh vegetables and fruits, whereas
high consumption of foods rich in nitrate and carcinogenic substances produced
during the cooking process increased the risk of GC
and Haemophilus
parainfluenzae
is increased in hypochlorydria due to atrophic gastritis, e.g during Helicobacter
pylori
infection). Until recently nitrate was perceived as a purely harmful dietary
component which causes infantile methaemoglobinaemia, carcinogenesis
and possibly even teratogenesis. Epidemiological studies have failed
to substantiate this. It has been shown that dietary nitrate undergoes
enterosalivary
circulation. It is recirculated in the blood, concentrated by the salivary
glands, secreted in the saliva and reduced to nitrite by
nitrate reductase+
Gram-positive facultative anaerobic nitrite-producing bacteria (NPB)
(Staphylococcus sciuri
and Staphylococcus
intermedius
>> Pasteurella spp.
> Streptococcus spp.,
Peptostreptococcus
spp.,
Veillonella
spp.,
Staphylococcus
aureus,
Staphylococcus
epidermidis,
Nocardia
spp.,
Corynebacterium
pseudodiphteriticum,
Fusobacterium
nucleatumref)
on the tongue. The proportion of culturable NPB in the total culturable
microbial population increases from 6% (105 CFUs/cm2)
on the anterior tongue to 65% (107 CFUs/cm2) on the
posterior tongue. Different species compositions of NPB are found on different
tongue sections with S. intermedius populations decreasing and S.
sciuri and Pasteurella populations increasing towards the posterior
tongue. Nitrite production is sensitive to oxygen, and significant nitrite
production is only detected on the posterior tongue where the majority
of bacteria are situated in deep clefts in the tongue surfaceref.
and Salmonella spp..
NO is known to have vasodilator properties and to modulate platelet function,
as are S-nitrosothiols. Thus, nitrate in the diet, which determines
reactive nitrogen oxide species production in the stomach (McKnight et
al. 1997), is emerging as an effective host defence against gastrointestinal
pathogens, as a modulator of platelet activity and possibly even of gastrointestinal
motility and microcirculation. Therefore dietary nitrate may have an important
therapeutic role to play, not least in the immunocompromised and in refugees
who are at particular risk of contracting gastroenteritides. A large amount
of N2O
produced in the intestine and normal nitrate intake do not influence the
breath NO concentration, probably due to its relatively small production.
Higher maximum N2O concentration after ingesting lettuce in
old subject is probably because more bacteria, which rapidly reduce dietary
nitrate in the upper intestinal tract, inhabit the gut in old age.
),
which is unable to transport oxygen from lungs to tissues and imparts a
brown hue to the blood. This etiology should be suspected when a
blood sample is brown and does not redden on exposure to air. Bacteria
in the gastrointestinal system mediate the conversion of nitrate to nitrite.
Consequently the risk of methemoglobinemia from ingestion of nitrate depends
not only on the dose of nitrate by also on the number and type of enteric
bacteria. In meat, the nitrite is bound to the myoglobin in the meat and
would therefore not be an issue in methemoglobinemia
and esophageal
squamous cell carcinoma (ESCC)
; long-term exposure to elevated nitrate levels in drinking water may contribute
to the risk of non-Hodgkin's
lymphoma (NHL)ref
is not of any benefit
))
the chemical at high dosages for their entire life span => autopsies and
histochemical examinations : this approach can detect both genotoxic and
nongenotoxic carcinogens.
Copyright © 2001-2005 Daniele Focosi.
All rights reserved
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