Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adults

Carol Johnston, Mei Fang Yen

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The effect of a megadose of ascorbic acid (AA) on glucose and insulin responses after an oral-glucose-tolerance test (OGTT) is unknown. With a double-blind, placebo-controlled design, nine normoglycemic subjects (22 ± 1 y, x̄ ± SEM) consumed AA (2 g/d) or placebo for 2 wk after a 2-wk washout period with placebo, and an OGTT was performed after an overnight fast. This 4-wk protocol was repeated in a crossover fashion. Plasma glucose was significantly elevated 1-h postprandial in vitamin C-saturated subjects vs those taking a placebo. The plasma insulin response curve was shifted rightward in vitamin C-saturated subjects relative to baseline: plasma insulin was significantly depressed at 0.5 h postprandial but significantly elevated at 2 h postprandial. These data indicate that elevated plasma AA delays the insulin response to a glucose challenge in normoglycemic adults, thereby prolonging the postprandial hyperglycemia. These effects might be partially explained by the competitive inhibition of glucose transfer into pancreatic β cells by high concentrations of circulating AA.

Original languageEnglish (US)
Pages (from-to)735-738
Number of pages4
JournalAmerican Journal of Clinical Nutrition
Volume60
Issue number5
StatePublished - Nov 1994

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megadose
Ascorbic Acid
insulin
ascorbic acid
Insulin
Glucose
glucose
placebos
Placebos
Glucose Tolerance Test
hyperglycemia
Hyperglycemia

ASJC Scopus subject areas

  • Food Science
  • Medicine (miscellaneous)

Cite this

Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adults. / Johnston, Carol; Yen, Mei Fang.

In: American Journal of Clinical Nutrition, Vol. 60, No. 5, 11.1994, p. 735-738.

Research output: Contribution to journalArticle

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