The importance of vitamin C for hydroxylation of vitamin D3 to 1,25(OH)2D3 in man

Clin Rheumatol. 1991 Jun;10(2):162-7. doi: 10.1007/BF02207657.

Abstract

The effects of vitamin C on 1,25(OH)2D3 synthesis in humans were evaluated; the study included 20 females. They were divided into 2 groups. The first of the 10 subjects (age range 55-71) received ascorbic acid at a dose of 150 mg/die i.v. for 10 days; the second 10 subjects (age range 55-69) received a placebo i.v. for 10 days. In a later study (after a 30-day washout) the same two groups were tested for the second time with ascorbic acid at a dose of 1,000 mg/die i.v. for 10 days and placebo i.v. for 10 days. Serum calcium and phosphorus, serum Ca++, serum proteins, blood and urinary pH, serum 25(OH)D3 and 1,25(OH)2D3, serum PTH, urinary hydroxyprolin were tested before and after the treatments. In the first study a significant increase in serum 1,25(OH)2D3 was observed after ascorbic acid while no significant variation was observed for the other parameters. In the second study, a significant increase in serum Ca++ and a significant decrease in serum 1,25(OH)2D3 were observed after ascorbic acid while no significant variation was observed for the other parameters. The authors conclude that ascorbic acid promotes 1,25(OH)2D3 synthesis at a paraphysiologic dose (150 mg/die) in humans but this synthesis is inhibited at higher doses (1,000 mg/die). The latter effect by Ca++ or by an effect of ascorbate on 1 alpha-hydroxylase enzyme could be mediated.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial

MeSH terms

  • Adult
  • Aged
  • Ascorbic Acid / pharmacology*
  • Calcitriol / biosynthesis*
  • Calcium / blood
  • Cholecalciferol / metabolism*
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Hydroxylation
  • Middle Aged
  • Parathyroid Hormone / blood
  • Phosphorus / blood

Substances

  • Parathyroid Hormone
  • Cholecalciferol
  • Phosphorus
  • Calcitriol
  • Ascorbic Acid
  • Calcium