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Fat transforms vitamin C from 'good cop' into 'bad cop'
September 04, 2007Fat in the stomach may cause vitamin C to promote, rather than prevent, the formation of certain cancer causing chemicals, reveals research published ahead of print in the journal Gut.
The researchers analysed the impact of both fat (lipid) and vitamin C (ascorbic acid) on nitrite chemistry in the upper (proximal) stomach, which is especially vulnerable to pre-cancerous changes and tumour growth.
Nitrites, which are present in human saliva, and in certain preserved foodstuffs, may be converted to cancer causing compounds called nitrosamines.
Nitrosamines are formed in acidic conditions, such as those afforded by stomach acid, but vitamin C inhibits their formation, by converting nitrite to nitric oxide.
The researchers replicated the chemical conditions of the proximal stomach and measured the formation of nitrosamines, oxygen, and nitric oxide.
Without fat, vitamin C curbed the levels of two nitrosamines by a factor of between five and 1000. And it completely eliminated the production of the other two.
But when 10% fat was added, vitamin C actually boosted the production of nitrosamines between 8 and 140-fold.
Fat remains in the proximal stomach for some time after a meal and also makes up a substantial amount of the cells lining the stomach, say the authors.
Nitric oxide is formed when vitamin C reacts with nitrite in acid. However, the nitric oxide can diffuse into fat and then react with oxygen to form nitrosoamine generating chemicals.
The findings may be relevant to the recent observations that vitamin C supplements fail to reduce cancer risk, say the authors.
BMJ Specialty Journals
Nitrosamines are formed in acidic conditions, such as those afforded by stomach acid, but vitamin C inhibits their formation, by converting nitrite to nitric oxide.
The researchers replicated the chemical conditions of the proximal stomach and measured the formation of nitrosamines, oxygen, and nitric oxide.
Without fat, vitamin C curbed the levels of two nitrosamines by a factor of between five and 1000. And it completely eliminated the production of the other two.
But when 10% fat was added, vitamin C actually boosted the production of nitrosamines between 8 and 140-fold.
Fat remains in the proximal stomach for some time after a meal and also makes up a substantial amount of the cells lining the stomach, say the authors.
Nitric oxide is formed when vitamin C reacts with nitrite in acid. However, the nitric oxide can diffuse into fat and then react with oxygen to form nitrosoamine generating chemicals.
The findings may be relevant to the recent observations that vitamin C supplements fail to reduce cancer risk, say the authors.
BMJ Specialty Journals
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Scientists have found that the human liver fluke (Opisthorchis viverrini) contributes to the development of bile duct (liver) cancer by secreting granulin, a growth hormone that is known to cause uncontrolled growth of cells.
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The Senate Commission of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) on the Investigation of Health Hazards of Chemical Compounds in the Work Area has presented the 2004 Maximum Allowable Concentration (Maximale Arbeitsplatzkonzentrationen - MAK) and Biological Tolerance Value (Biologische Arbeitsstofftoleranzwerte - BAT) list and submitted it to the German Federal Minister of Economics and Labour. It contains suggestions for MAK values, i.e., the maximum allowable concentration of a working substance in the workplace atmosphere as a gas, steam or aerosol that according to current knowledge does not impair the health of employees exposed during eight-hour working da
Study Examines Role of Helicobacter Pylori in Esophageal Cancer Development
Infection with bacteria that can cause peptic ulcers and distal stomach cancer may be associated with a reduced risk of a type of esophageal cancer called adenocarcinoma, according to a study in the March 3 issue of the Journal of the National Cancer Institute. However, that same study found that people infected with the bacteria, called Helicobacter pylori, who also had gastric atrophy, or "wasting" of the mucous membrane that lines the stomach, were at an increased risk of another type of esophageal cancer called squamous-cell carcinoma. Earlier studies have suggested that H. pylori infection may be associated with a reduced risk of esophageal adenocarcinoma (cancer that arises in the ti
Peptic ulcer surgery increases the risk of pancreatic cancer
Peptic ulcer surgery seems to increase the risk of developing pancreatic cancer, finds research in the Journal of Clinical Pathology.
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