RESUMO
Free radicals and reactive species produced in vivo can trigger cell damage and DNA modifications resulting in carcinogenesis. Dietary antioxidants trap these species limiting their damage. The present study evaluated the role of vitamins C and E in the prevention of potentially premalignant modifications to DNA in the human stomach by supplementing patients who, because of hypochlorhydria and possible depletion of gastric antioxidants, could be at increased risk of gastric cancer. Patients undergoing surveillance for Barrett's oesophagus (n 100), on long-term proton pump inhibitors were randomized into two groups: vitamin C (500 mg twice/d) and vitamin E (100 mg twice/d) for 12 weeks (the supplemented group) or placebo. Those attending for subsequent endoscopy had gastric juice, plasma and mucosal measurements of vitamin levels and markers of DNA damage. Seventy-two patients completed the study. Plasma ascorbic acid, total vitamin C and vitamin E were elevated in the supplemented group consistent with compliance. Gastric juice ascorbic acid and total vitamin C levels were raised significantly in the supplemented group (P=0.01) but supplementation had no effect on the mucosal level of this vitamin. However, gastric juice ascorbic acid and total vitamin C were within normal ranges in the unsupplemented group. Mucosal malondialdehyde, chemiluminescence and DNA damage levels in the comet assay were unaffected by vitamin supplementation. In conclusion, supplementation does not affect DNA damage in this group of patients. This is probably because long-term inhibition of the gastric proton pump alone does not affect gastric juice ascorbate and therefore does not increase the theoretical risk of gastric cancer because of antioxidant depletion.
Assuntos
Acloridria/genética , Antiácidos/efeitos adversos , Antioxidantes/uso terapêutico , Transformação Celular Neoplásica/efeitos dos fármacos , Dano ao DNA , Suplementos Nutricionais , Acloridria/metabolismo , Adulto , Idoso , Antioxidantes/farmacocinética , Ácido Ascórbico/farmacocinética , Ácido Ascórbico/uso terapêutico , Esôfago de Barrett/genética , Esôfago de Barrett/metabolismo , Feminino , Determinação da Acidez Gástrica , Suco Gástrico/metabolismo , Mucosa Gástrica/metabolismo , Humanos , Concentração de Íons de Hidrogênio/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/metabolismo , Inibidores da Bomba de Prótons , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismo , Vitamina E/farmacocinética , Vitamina E/uso terapêuticoRESUMO
Seventeen patients on constant doses of pancreatic enzymes were randomised to receive either cimetidine or placebo for either of two successive six month periods. Nutritional state and maldigestion were assessed at the beginning and end of each period. Reductions in mean values of faecal fat, nitrogen, wet weight, and bile salts of approximately 30% were found on cimetidine therapy. Results showed considerable variation and only the fall in faecal fat was statistically significant. No benefit was demonstrated for height, weight, skinfold thickness, albumin, vitamin A, bone age or Crispin-Norman score.