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Articles by S. E Vollset
Total Records ( 2 ) for S. E Vollset
  A Vogiatzoglou , A Oulhaj , A. D Smith , E Nurk , C. A Drevon , P. M Ueland , S. E Vollset , G. S Tell and H. Refsum

Background: Methylmalonic acid (MMA) in plasma or serum is widely used for assessment of vitamin B12 status. However, data are sparse regarding factors, besides renal function, that may influence MMA concentrations. We searched for important determinants of plasma MMA in the general population.

Methods: In 6946 middle-aged (47–49 years) and elderly (71–74 years) individuals from the Hordaland Homocysteine Study in Norway, we collected anthropometric measurements, lifestyle data, and plasma MMA, vitamin B12, and creatinine measurements. For 5820 individuals, we also collected dietary data.

Results: Age and plasma creatinine were positively associated with plasma MMA, whereas plasma vitamin B12 was negatively associated. These variables together with sex were the strongest determinants of plasma MMA, accounting for 16% of the variation (R2 = 0.16). Addition of anthropometric measures and lifestyle and dietary factors only gave slight improvement (total R2 = 0.167). Increased plasma MMA was seen when plasma vitamin B12 was <400 pmol/L. In individuals with vitamin B12 ≥400 µmol/L (vitamin B12–replete), the 2.5th–97.5th percentile reference limits for MMA were 0.10–0.28 µmol/L (middle-aged) and 0.10–0.36 µmol/L (elderly). When plotted against creatinine (nomograms), the 97.5th percentile of MMA was similar in men and women but approximately 0.15 µmol/L higher in elderly than middle-aged individuals. Vitamin B12–replete participants had MMA upper limits approximately 0.1 µmol/L (elderly) and 0.04 µmol/L (middle-aged) below those of the unselected population at all creatinine concentrations.

Conclusions: Identified determinants accounted for <17% of the overall variation in plasma MMA. The difference in MMA between middle-aged and elderly individuals is only partly explained by creatinine and vitamin B12 concentrations.

  A Ulvik , M Ebbing , S Hustad , O Midttun , O Nygard , S. E Vollset , K. H Bonaa , J. E Nordrehaug , D. W Nilsen , H Schirmer and P. M. Ueland

Background: Smoking is associated with decreased concentrations of several antioxidant vitamins. We sought to determine the relation between circulating concentrations of selected B vitamins and smoking status, with particular attention to longitudinal associations.

Methods: We used baseline data from 2 B-vitamin intervention trials that included 6837 patients with ischemic heart disease. Smoking habits were ascertained by interview. Vitamins and metabolites, including the nicotine metabolite cotinine, were measured in plasma and serum by microbiological assays or gas/liquid chromatography–tandem mass spectrometry.

Results: The highest circulating concentrations of folate and pyridoxal 5'phosphate (PLP) and lowest concentrations of total plasma homocysteine, a functional marker of folate status, were observed for self-reported never smokers, followed by self-reported ex-smokers and current smokers (Ptrend < 0.001). Cobalamin and its functional marker methylmalonic acid were not associated with smoking status. Based on their low cotinine concentrations, we were able to identify a group of smokers that had abstained from smoking for 3 days or more. Compared with smokers with high plasma cotinine, smokers with low cotinine had significantly higher circulating concentrations of folate, PLP, and riboflavin (all P < 0.005), and this trend continued for ex-smokers, with increasing time since smoking cessation.

Conclusions: Smoking lowered circulating concentrations of folate, PLP, and riboflavin, but concentrations increased significantly after a few days of smoking cessation. We propose that short-term effects may be related to acute smoking-induced oxidative stress, whereas the longer-lasting effects among ex-smokers may reflect changes in diet and/or restoration of vitamin concentrations in tissue during the first few months to years after smoking cessation.

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