Lack of an effect of multivitamins containing vitamin A on serum retinyl esters and liver function tests in healthy women.

Abstract

Two hundred eighty-four female adults (aged 40-70 years) were longitudinally studied to investigate the relationship between dietary supplemental vitamin A and serum biochemical markers of vitamin A toxicity. Serum retinol, retinyl esters, and retinol-binding protein (RBP), alkaline phosphatase and aspartate aminotransferase activities and bile acids were measured at baseline, 1 and 2 years. Fasting serum retinol and retinyl ester concentrations were determined by high-performance liquid chromatography, and dietary and supplemental intake of vitamin A were assessed by 3-day food records. There was no difference in dietary vitamin A intake between supplement users and nonusers. In supplemental users, the mean +/- SEM supplemental vitamin A intake was 952 +/- 81 IU/day (range 250-5000 retinol equivalents/day). Serum retinol, retinyl esters, and RBP concentrations were not different between the two groups during the 2-year period. For each group, serum retinyl esters significantly increased over time (p < 0.03), but the magnitude of the increase was not different between the groups. Serum levels of retinol, retinyl esters, and RBP were not correlated with vitamin A intake or age in either group. Biochemical measures of liver damage (serum alkaline phosphatase and aspartate aminotransferase activities and serum bile acids) were not related to serum retinol, retinyl esters or RBP concentrations, nor were they different between nonusers and users of supplemental vitamin A. This study provides evidence that long-term supplemental vitamin A in doses commonly found in multivitamin supplements does not present a risk for hypervitaminosis A.

Safety of <7500 RE (<25000 IU) vitamin A daily in adults with retinitis pigmentosa

“…Elevated triacylglycerols might be attributed to the competition for lipoprotein lipase between triacylglycerols, the preferred substrate, and retinyl esters, both of which are hydrolyzed by this enzyme (41). As reported by others (33), this possibility was supported by the direct correlation between fasting triacylglycerols and retinyl esters in our data. A correlation was also found between serum retinol and triacylglycerols.…”

“…5 x -± SD. Previous studies presented an inconsistent picture of the serum retinol response, which was either elevated or unaffected depending in part on the level of vitamin A supplementation (25,(33)(34)(35). Nonetheless, highly elevated serum retinol in excess of 3.49 mol/L (100 g/dL) usually is a diagnostic indicator of excess vitamin A intake and hypervitaminosis A (6,8).…”

HPLC Assessment and Multivariate Predictability of Serum Retinol and α-Tocopherol Concentrations in Adult Female Subjects

“…Considering the costs related to treatment of the patients in the risk groups and logistic difficulties in estimating reliable retinol and -tocopherol status, our results on the multivariate linear regression model may be useful for identifying groups at risk of inadequacy or deficiency. However, as in some previous studies [15,18,48,50,52,58], our findings indicated that dietary intake of vitamin A and E are poor predictors for serum retinol and -tocopherol concentrations. The main finding of our study is that obesity in apparently healthy adult female subjects is not associated with decreased serum retinol and -tocopherol levels.…”

“…No correlation between dietary vitamin A and serum retinol level may be due to the fact that the amount of retinol in the circulating body pool is highly regulated and is essentially homeostatically controlled to body stores [8]. Some studies have also shown that iron deficiency seems to deteriorate vitamin A metabolism leading to reduction of serum retinol [51] and that vitamin A supplementation did not affect serum retinol concentrations [17,[52][53][54]. Whereas, it was observed that vitamin E intake was significantly associated with serum concentrations of -tocopherol only when vitamin supplement users were included in the analyses [14,17,[55][56][57].…”

Nutritional assessment of serum and hepatic vitamin A levels in patients with cirrhosis

“…22 A study of 84 healthy women suggested that long-term supplemental vitamin A in doses commonly found in multivitamin supplements does not present a risk for hypervitaminosis A. 23 Such information is not available for patients with cirrhosis. In our study, high fasting concentrations of serum retinyl esters did not appear to indicate hypervitaminosis A because our patients had low hepatic values for retinyl esters, and consumption of vitamin A supplements was an exclusion criterion for the study.…”