Folic acid metabolism in normal, folate deficient and alcoholic man

In vivo kinetics of folate metabolism

Investigation of the in vivo kinetics of folate metabolism provides information that contributes to a better understanding of the manner in which this vitamin is processed in vivo. Kinetic studies can yield insight into the requirements for folate, especially with respect to factors that may lead to increased requirements. This review considers the strengths and weaknesses of various approaches to the study of folate kinetics and resulting data, followed by a summary and interpretation of existing data.

Study of dose-dependence and urinary folate excretion produced by ethanol in humans and rats

Acute ethanol ingestion by human alcoholic subjects produces a marked decrease in serum folate levels within 16 hr. A similar decrease occurs in rats and can be explained by a marked increase in urinary folate excretion following ethanol treatment. To assess the effects of acute ethanol ingestion on urinary folate excretion in healthy human volunteers, two studies were carried out at initial ethanol dose levels of 0.8 g/kg and 1.0 g/kg, respectively. Blood ethanol levels peaked at 70 mg/dl in the first study, but in the second study were 100 +/- 20 mg/dl through 6 hr. Only in the second study were urinary folate levels significantly increased by ethanol administration, and this 8 hr after ingestion. This increase was accompanied by a decrease in urine volume so that in neither study was the total amount of urinary folate excreted from 0-12 hr increased by ethanol ingestion. Studies with various dose levels of ethanol in rats showed that there was a linear dose-response relationship between the total urinary folate excretion and the dose of ethanol. Peak urinary ethanol levels also correlated with urinary folate excretion. These results suggest that doses of ethanol larger than 1.0 g/kg produce increases in urinary folate excretion and that the inability to observe large increases in studies in human subjects is probably related to the limited doses of ethanol chosen.

Macrocytosis in alcohol-related liver disease: its value for screening

The incidence of macrocytosis, defined as a mean corpuscular volume (MCV) of greater than 95 fl and large red cells on peripheral blood film, was determined in 303 alcoholics with liver disease (95 females: 208 males), 60 non-alcoholics with chronic liver disease (44 females: 16 males) and 35 control subjects (15 females: 20 males). Macrocytosis was found in 70.3% (213/303) of alcoholics with liver disease and in 23.3% (14/60) of non-alcoholics with liver disease, P less than 0.001. MCV values greater than 100 fl were seen in 49.5% (150/303) of alcoholics, but in only 3.3% (2/60) of non-alcoholics, P less than 0.001. Macrocytosis was more frequent in female, 86.3% (82/95) than in male alcoholics 63.0% (131/208), P less than 0.001. Serum folate values less than 3 microgram/l were found in 14.5% (44/303) of alcoholics and in 11.7% (7/60) of non-alcoholics. Low serum folate values were found in 18.3% (39/213) of alcoholics with macrocytosis and in 35.9% (28/78) of those with macrocytic anaemia. Twenty alcoholics with pre-cirrhotic liver disease were followed over three months. Macrocytosis was present in 85.0% (17/20) at the outset and in 40% (8/20) 3 months later. The changes in MCV were independent of alcohol intake and serum folate values. Macrocytosis is a useful diagnostic indicator of alcoholism. MCV values greater than 100 fl in patients with liver disease almost invariably indicate alcohol-related disease. In the short-term, changes in MCV are of little use in monitoring alcohol intake.

Acute folate deficiency associated with intravenous nutrition with aminoacid-sorbitol-ethanol: prophylaxis with intravenous folic acid

Preoperative folate levels were initially normal in 30 patients with gastrointestinal tract disease but fell within 48 h by 60-95% in 20 patients who received intravenous nutrition for 6-12 d with aminoacid-sorbitol-ethanol (ASE). This depression persisted in patients not given folate supplements. Folate levels in 10 control patients not given ASE showed only minimal decline. Haematological changes were reduced to a minimum in 10 patients given 0.5 mg i.v. folic acid daily whilst eight unsupplemented patients showed evidence of megaloblastic haemopoiesis. Three of these eight patients developed thrombocytopenia and/or leukopenia which was fatal in one patient.