Erythorbic acid is a stereoisomer of ascorbic acid with similar properties. Erythorbic acid is widely used as an antioxidant in processed foods.

Erythorbic Acid Research
Erythorbic acid is a potent enhancer of nonheme-iron absorption.
Am J Clin Nutr. 2004 Jan;79(1):99-102.
Institute of Food Science and Nutrition, Swiss Federal Institute of Technology, Zurich, Rueschlikon, Switzerland.
The aims of the present study were to evaluate the effect of erythorbic acid on iron absorption from ferrous sulfate at molar ratios of 2:1 and 4:1 (relative to iron) and to compare the effect of erythorbic acid directly with that of ascorbic acid at a molar ratio of 4:1. DESIGN: Iron absorption from iron-fortified cereal was measured in 10 women on the basis of erythrocyte incorporation of stable iron isotopes ((57)Fe or (58)Fe) 14 d after administration. Each woman consumed 4 ferrous-sulfate-fortified test meals (containing 5 mg Fe/meal) with or without added erythorbic or ascorbic acid. The data were evaluated by use of paired t tests, and the results are presented as geometric means. RESULTS: Iron absorption from the test meal without any added enhancer was 4.1%. The addition of erythorbic acid (at molar ratios of 2:1 and 4:1 relative to iron) increased iron absorption 2.6-fold (10.8%; P < 0.0001) and 4.6-fold (18.8%; P < 0.0001), respectively. The addition of ascorbic acid (molar ratio of 4:1) increased iron absorption 2.9-fold (11.7%; P = 0.0004). At a molar ratio of 4:1, erythorbic acid was 1.6-fold (P = 0.0002) as potent an enhancer of iron absorption as was ascorbic acid. CONCLUSION: Although erythorbic acid is a potent enhancer of iron absorption, its lack of antiscorbutic activity limits its usefulness in iron-fortification programs. However, it may play a major role in enhancing iron bioavailability from mixed diets that include foods preserved with erythorbic acid.

Effect of smoking on erythorbic acid pharmacokinetics.
Br J Nutr. 2003 May;89(5):667-71. Department of Pharmacology and Pathobiology, Royal Veterinary and Agricultural University, Copenhagen, Denmark.
Smoking significantly lowers the concentration of plasma antioxidants. Acorbic acid has recently been shown to be depleted by smoking per se. However, the direct cause of ascorbate depletion remains unclear. Erythorbic acid is a stereoisomer of ascorbic acid commonly used as antioxidant in foodstuffs and has the same redox properties as ascorbic acid. We therefore investigated if erythorbic acid could be used as a non-isotopic marker of smoking-induced oxidative stress. In a sample of smokers (n 10) and non-smokers (n 10), the pharmacokinetics of erythorbic acid were followed after a single oral dose (1 g) and subsequently, the effect of a 2-week ascorbic acid supplementation (0.5 g/d) on erythorbic acid kinetics was studied in a double-blind, placebo-controlled fashion. Our present results do not suggest that altered pharmacokinetics is likely to play a major role in the ascorbic acid depletion consistently observed in smokers.