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The Science Behind Ester-C

“24-hour immune support”

Ester-C is an absorbable, non-acidic form of vitamin C and is created through a unique water based production process which neutralizes ascorbic acid with calcium carbonate to create calcium ascorbate and the metabolites of vitamin C, such as calcium threonate. The Ester-C mechanism of action has been investigated in various models. Laboratory studies have shown that exposing animal or human cells to calcium threonate increases the uptake of vitamin C by these cells [1, 2]. This improved cellular uptake may further facilitate the retention of vitamin C in the body. In preclinical models, Ester-C exhibited a higher plasma concentrations and less rapid excretion of vitamin C than ascorbic acid [3].

The White blood cells (WBCs), as an important component of the body’s immune system, are vital in the maintenance of overall health. Phagocytes consume extracellular vitamin C when the immune system is activated, causing plasma and WBC vitamin C concentrations to decline rapidly during activated stress to the body[4]. Furthermore, certain populations, including those with heart[5], blood sugar [6,7] and lung [8] health concerns have been reported to have reduced WBC vitamin C concentrations compared to the general population. Repletion of vitamin C has been shown to help assist with the health of these important functions [9]. An increased retention of vitamin C in WBCs is conducive to providing maximum cellular concentrations of vitamin C for optimum biochemical activity, including immune function.

A series of human randomized controlled trials have shown that vitamin C from Ester-C can be retained in WBCs longer than ascorbic acid [10] [11, 12](data on file). Furthermore, the supplementation of Ester-C has demonstrated significant benefits to immune health in men and women compared to placebo over a 60-day period from November to February [13]. This study has also been cited in the 2007 and 2013 Cochrane reviews describing the role of vitamin C in support of immune system health [14, 15]

“Gentle on the stomach”

Large doses of vitamin C behave differently in the body and bring profound biological effects. The acidic nature of ascorbic acid can be associated with adverse gastrointestinal effects, particularly in people who are sensitive to acidic foods. A higher prevalence of epigastric adverse effects were observed when ascorbic acid was consumed compared to Ester-C (62.5% vs. 37.5%) in healthy volunteers with acid sensitivity and statistically more participants rated “very good” tolerability of Ester-C compared to ascorbic acid (72% vs. 54%) [16]. Additionally, a significant worsening of abdominal pain and diarrhea was observed when given ascorbic acid, while no significant changes were seen when given Ester-C [17]. These results support that Ester-C, as a non-acidic form of vitamin C, is gentler on the stomach than ascorbic acid.


1. Fay, M.J. and A.J. Verlangieri. Life Sci, 1991. 49(19): p. 1377-81.
2. Fay, M.J., M.J. Bush, and A.J. Verlangieri,. Gen Pharmacol, 1994. 25(7): p. 1465-9.
3. Bush, M.J. and A.J. Verlangieri. Res Commun Chem Pathol Pharmacol, 1987. 57(1): p. 137-40.
4. Stankova, L., et al. Infect Immun, 1975. 12(2): p. 252-6.
5. Wintergerst, E.S., S. Maggini, and D.H. Hornig. Ann Nutr Metab, 2006. 50(2): p. 85-94.
6. Ramirez, J. and N.C. Flowers. Am J Clin Nutr, 1980. 33(10): p. 2079-87.
7. Akkus, I., et al.. Clin Chim Acta, 1996. 244(2): p. 221-7.
8. Shidfar, F., et al.. East Mediterr Health J, 2005. 11(1-2): p. 87-95.
9. Jayachandran, M., et al. . Journal of Anti-Aging Medicine, 2000. 3(1): p. 37-42.
10. Moyad, M.A., et al. Adv Ther, 2008. 25(10): p. 995-1009.
11. Mitmesser, S., M. Combs, and M. Evans. The FASEB Journal, 2014. 28(1 Supplement).
12. Wright JV, S.R., Kirk FR. International Clinical Nutrition Review, 1990. 10(1): p. 7-10.
13. Van Straten, M. and P. Josling. Adv Ther, 2002. 19(3): p. 151-9.
14. Hemila, H., E. Chalker, and B. Douglas Cochrane Database Syst Rev, 2007(3): p. CD000980.
15. Hemila, H. and E. Chalker. Cochrane Database Syst Rev, 2013. 1: p. Cd000980.
16. Gruenwald, J., et al.. Adv Ther, 2006. 23(1): p. 171-8.
17. Ye, Q., M. Combs, and S. Mitmesser. The FASEB Journal, 2015. 29(1 Supplement).

* These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.

† Ester C® stays in your white blood cells for up to 24 hours, which is longer than regular vitamin C. White blood cells are an important component of your immune system.

1 Moyad MA, Combs MA, Vrablic AS, Velasquez J, Turner B, Bernal S. Adv. Ther. 2008 Oct: 25(10): 995-1009.

2 Gruenwald, J. et al. 2006. Advances in Therapy. 23(1): Jan-Feb: 171-8.

U.S. patent Nos: 6,197,813 and 6,878,744.

♦ Tablets only.