Effect of smoking on serum concentrations of total homocysteine and B vitamins in mid-pregnancy

There are conflicting findings in the literature on the effect of smoking o n total homocysteine (tHcy) concentrations in non-pregnant subjects. We eva luated the effect of smoking on serum concentrations of tHcy, folate, vitam in B-12 pyridoxal 5'-phosphate (PLP, a coenzyme form of vitamin B-6) in 196 women at 18 and 30 weeks' gestation. The smokers were defined as those who self-reported cigarette smoking and had serum concentrations of thiocyanat e, a biomaker of smoking, in the highest quartiles of the population. Mid-p regnancy serum tHcy concentrations were not significantly different between smokers and non-smokers. Folate, vitamin B-12 and PLP concentrations were generally lower in smokers than non-smokers. In smokers, tHcy concentration s had significant negative correlations with folate at both time points. Th e multiple regression analyses indicated that serum folate concentration wa s the most significant factor associated with tHcy concentrations among smo kers, whereas thiocyanate concentrations showed no such effect. We conclude that serum tHcy concentrations were most strongly associated with the nutr itional status of folate among the B vitamins tested during mid-pregnancy i n our subjects. We suggest that it is essential to consider the nutritional status of folate, vitamin B-12 and vitamin B-6 in evaluating the effect of smoking on homocysteine metabolism. (C) 2001 Published by Elsevier Science B.V.