Effect of Vegetarianism and Smoking on Vitamin B 12 , Thiocyanate, and Folate Levels in the Blood of Normal Subjects

Vitamin B(12), thiocyanate, and folate levels in the blood were estimated in 69 apparently normal subjects, of whom 26 were non-vegetarian non-smokers, 19 non-vegetarian smokers, 15 vegetarian non-smokers, and nine vegetarian smokers. The serum total (cyanide-extracted) B(12) level (value A) ranged from 105 to 728 pg/ml, with a mean of 292 pg/ml. The highest values were found in non-vegetarian non-smokers and the lowest in vegetarian smokers. There was no significant difference in value A between smokers as a group and non-smokers as a group. On the other hand, in vegetarians value A was very significantly lower than in non-vegetarians regardless of their smoking habits.It is suggested that A may represent both the protein-bound and free forms of vitamin B(12) in the blood, and B mainly the free B(12), which may be the physiologically active form. The plasma thiocyanate level varied from 1.0 to 15 mumol/100 ml, being, as expected, much higher in smokers (mean 8.20 mumol/100 ml) than in non-smokers (mean 2.02 mumol/100 ml). There was a rough correlation between falling B(12) levels and rising thiocyanate levels. The serum folate level ranged from 2.75 to 15.75 ng/ml, and was slightly but significantly higher in vegetarians (mean 6.60 ng/ml) than in non-vegetarians (mean 4.79 ng/ml), reflecting the greater content of folate in a vegetarian diet.