Vitamin C: should we supplement?

Abstract

Purpose of review: Hypovitaminosis C and vitamin C deficiency are very common in critically ill patients due to increased needs and decreased intake. Because vitamin C has pleiotropic functions, deficiency can aggravate the severity of illness and hamper recovery.

Recent findings: Vitamin C is a key circulating antioxidant with anti-inflammatory and immune-supporting effects, and a cofactor for important mono and dioxygenase enzymes. An increasing number of preclinical studies in trauma, ischemia/reperfusion, and sepsis models show that vitamin C administered at pharmacological doses attenuates oxidative stress and inflammation, and restores endothelial and organ function. Older studies showed less organ dysfunction when vitamin C was administered in repletion dose (2-3 g intravenous vitamin C/day). Recent small controlled studies using pharmacological doses (6-16 g/day) suggest that vitamin C reduces vasopressor support and organ dysfunction, and may even decrease mortality.

Summary: A short course of intravenous vitamin C in pharmacological dose seems a promising, well tolerated, and cheap adjuvant therapy to modulate the overwhelming oxidative stress in severe sepsis, trauma, and reperfusion after ischemia. Large randomized controlled trials are necessary to provide more evidence before wide-scale implementation can be recommended.

Box 1

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FIGURE 1

Pathophysiological pathways after a primary insult (trauma, ischemia/reperfusion injury, sepsis) which induces oxidative stress and systemic inflammation, and can lead to remote organ dysfunction. IL-1β, interleukin-1β; IL-6, interleukin-6; NF-κB, nuclear factor-κB; NO, nitric oxide; TNF-α, tumor necrosis factor-α.

FIGURE 2

Pathways of oxalate biosynthesis.