Effect of vegetarianism and smoking on vitamin B12, 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.