Effects of smoking on metabolism and excretion of vitamin B12.

Abstract

Experimental and clinical evidence both suggest that there is some connexion between the metabolism of vitamin B,2 and that of cyanide, and that smoking, which is associated with a high cyanide intake-for example, Darby and Wilson (1967)-may adversely affect B12 metabolism (Boxer and Rickards, 1952;Wokes and Picard, 1955;Braekkan, Njaa, and Utne, 1957;Wokes, 1958;Smith, 1961;Smith, Duckett, and Waters, 1963;Smith, 1964;Smith and Duckett, 1965;Matthews, Wilson, and Zilkha, 1965 ;Wilson and Matthews, 1966;Lindstrand, Wilson, and Matthews, 1966;Smith and Foulkes, 1966). The hypothesis that interconnected disturbances of cyanide/B,2 metabolism may be concerned in the pathogenesis of tobacco amblyopia, the retrobulbar neuritis of pernicious anaemia, Leber's optic atrophy, and certain tropical neurological syndromes apparently associated with a high cyanide intake from cassava (Smith, 1961;Wilson, 1965;Montgomery, 1965;Wilson and Langman, 1966;Monekosso and Wilson, 1966; Freeman, 1967;Chisholm, Bronte-Stewart, and Foulds, 1967) makes it essential to obtain further information about the interrelationships between an increased exogenous cyanide load, cyanide/thiocyanate metabolism, and bodily handling of vitamin B, .So far the observations apparently providing a direct link between smoking and B12 metabolism are few. They include:(1) the observation that there may be a slight or moderate increase in cyanocobalamin in the plasma of some heavy smokers (Lindstrand, Wilson, and Matthews, 1966); (2) the finding that a larger proportion of serum B12 is extractable in the absence of added cyanide in smokers than in non-smokers, which may be related to (1); and (3) the finding of a negative correlation between plasma cyanide concentration and that of total serum B12 (Matthews et al., 1965 ;Wilson and Matthews, 1966 (Fig. 2). Extrapolation of the regression line in Fig. 2 suggests that if the urine

Effect of smoking on folate levels in buccal mucosal cells

“…levels than nonsmokers (Linnell et al, 1968;Dastur et al, 1972). Plasma folate levels were even lower in smokers with potentially premalignant bronchial squamous metaplasia than in smokers without metaplasia (Heimburger et al, 1987).…”

Vitamin B12

“…Cigarette smokers, but not nonsmokers, showed a high urinary thiocyanate excretion, which was associated with increased vitamin B12 excretion and a relatively low serum B12 concentration (Linnell et al, 1968). Because urinary thiocyanate excretion is an index of cyanide detoxication, it appears possible that a high plasma cyanide concentration caused through smoking disturbs the equilibrium between plasma and urinary vitamin B12.…”

Hematological Parameters and Cobalamin Status in Infants Born to Smoking Mothers

“…Smokers tend to have a lower nutrient intake than nonsmokers [44]. Low levels of cobalamin in smokers have also been attributed to cyanide detoxification and increased urinary excretion of the vitamin [17].…”

“…Smoking has been associated with reduced levels of cobalamin in adults [17,42,43], in pregnant women [18,19], and in neonates born to smoking mothers [19]. Smokers tend to have a lower nutrient intake than nonsmokers [44].…”

“…In adults, smoking is associated with decreased levels of cobalamin and folate [17][18][19][20] and elevated levels of total homocysteine (tHcy) [21]. Both low folate and cobalamin levels and high tHcy concentrations have been associated with an adverse pregnancy outcome [22][23][24].…”