If I recall correctly, Vitamin C plays an important role in the body's immune system. Anecdotal testing by myself gave me the impression that I could ward off a developing cold by the intake of high doses of Vitamin C.

In a pharmacy, I've now come across "Ester-C", claiming to be a reaction product of the ascorbic acid and something else. It was marketed as "the better Vitamin C", because it was alleged that it was better absorbed by the body, and better tolerated than the acid itself.

Now, as good and important Vitamin C might be, there's a lot of hyper around vitamin supplements, so I'm skeptical about these claims. Here my question: Does Ester C have the same health benefits as common vitamin C (ascorbic acid) and, in addition, is it better tolerated and absorbed?

  • Not part of my answer, because I don't really know it, but I would suspect that many other Vitamin C preparations are also calcium ascorbate and not the free acid. I wouldn't assume that most Vitamin C products are just the free acids, but I didn't check if that is the case. – Mad Scientist May 9 '11 at 19:46

They state two differences between their product and plain Vitamin C

  • It is not the free ascorbic acid but the calcium salt
  • Vitamin C metabolites are present

The first aspect is supposed to lead to a better tolerance of the Vitamin C, as the calcium ascorbate is less acidic than the free ascorbic acid. The metabolites are supposed to increase the absorption of Vitamin C, according to the claims of the company behind Ester-C

On their homepage the company lists the two following studies as evidence for their claims:

The study about Vitamin C absorption found no difference in plasma levels, but a difference in the Vitamin C level in leukocytes:

No significant difference in plasma vitamin C levels was observed when comparing the different preparations. However, at 24 hours, calcium ascorbate with metabolites resulted in significantly higher concentrations of vitamin C in leukocytes (P<0.0001) compared with vitamin C alone.

The study investigating if Ester-C is better tolerated found a positive effect:

Investigators concluded that Ester-C compared with AA caused significantly fewer epigastric adverse effects in participants sensitive to acidic foods and that Ester-C is much better tolerated.

There is a third, older study not mentioned on the website that reportedly did not find any difference in Vitamin C absorption between Ester C and other products:

Comparison of the absorption and excretion of three commercially available sources of vitamin C.

Unfortunately this one does not have an abstract and the article is not freely available, I have to rely on the second-hand reporting for this one.

Those are pretty small studies (15 persons in the first one, 50 in the second one), I don't think they can settle those questions on their own. The absorption claim in general is not validated by the studies, except for the leukocytes. The better tolerance of the calcium ascorbate seems to be supported by one of the studies.

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