Vitamin C : What is the difference between L ascorbic acid and ascorbic acid?

In the rapidly expanding market of dietary supplements, it is possible to find vitamin C in many different forms with many claims regarding its efficacy or bioavailability. Bioavailability refers to the degree to which a nutrient (or drug) becomes available to the target tissue after it has been administered.

Vitamin C also known as, ascorbic acid, L-ascorbic acid, dehydroascorbic acid, the antiscorbutic vitamin, L-xyloascorbic acid and L-threo-hex-2-uronic acidy-lactone, is a much talked about vitamin, with people claiming it as a cure-all for may diseases and problems - from cancer to the common cold.

Yet, this miracle vitamin cannot be manufactured by the body, and needs to be ingested.

The Bioavailability of Different Forms of Vitamin C (Ascorbic Acid) : 
Natural vs. synthetic ascorbic acid
Natural and synthetic L-ascorbic acid are chemically identical, and there are no known differences in their biological activity. The possibility that the bioavailability of L-ascorbic acid from natural sources might differ from that of synthetic ascorbic acid was investigated in at least two human studies, and no clinically significant differences were observed.

• A study of 12 males (six smokers and six nonsmokers) found the bioavailability of synthetic ascorbic acid (powder administered in water) to be slightly superior to that of orange juice, based on blood levels of ascorbic acid, and not different based on ascorbic acid in leukocytes (white blood cells). 
• A study in 68 male nonsmokers found that ascorbic acid consumed in cooked broccoli, orange juice, orange slices, and as synthetic ascorbic acid tablets are equally bioavailable, as measured by plasma ascorbic acid levels.

Ester-C® contains mainly calcium ascorbate, but also contains small amounts of the vitamin C metabolites dehydroascorbate (oxidized ascorbic acid), calcium threonate, and trace levels of xylonate and lyxonate. In their literature, the manufacturers state that the metabolites, especially threonate, increase the bioavailability of the vitamin C in this product, and they indicate that they have performed a study in humans that demonstrates the increased bioavailability of vitamin C in Ester-C®. This study has not been published in a peer-reviewed journal. A small published study of vitamin C bioavailability in eight women and one man found no difference between Ester-C® and commercially available ascorbic acid tablets with respect to the absorption and urinary excretion of vitamin C. Ester-C® should not be confused with ascorbyl palmitate, which is also marketed as "vitamin C ester".


What is the difference between Ester-C and regular Vitamin C? 

• Mostly the acidity. Regular vitamin C is very acidic, and can cause increases in your blood acidity levels.  Ester C is made so that it is non-acidic, and has more bio-flavanoids in it.  This is a fancy word for additional nutrients to allow your body to absorb it better.

Vitamin C with bioflavonoids

Bioflavonoids or flavonoids are polyphenolic compounds found in plants. Vitamin C-rich fruits and vegetables, especially citrus fruits, are often rich sources of flavonoids as well. There is little evidence that the bioflavonoids in most commercial preparations increase the bioavailability or efficacy of vitamin C.

The effect of bioflavonoids on the bioavailability of ascorbic acid has been examined in two published studies. A study of five men and three women found that a 500 mg supplement of synthetic ascorbic acid, given in a natural citrus extract containing bioflavonoids, proteins, and carbohydrates, was more slowly absorbed and 35% more bioavailable than synthetic ascorbic acid alone, wheen based on plasma levels of ascorbic acid over time and 24-hr urinary excretion of ascorbic acid. In that study, the ratio of bioflavonoids to ascorbic acid (weight per weight) was 4:1, which is much higher than most commercially available products. Another study in 7 seven omen and one man found no difference between the bioavailability of 500 mg of synthetic ascorbic acid and that of a commercially available vitamin C preparation with added bioflavonoids, where the ratio of bioflavonoids to ascorbic acid was 0.05:1.

Kidney Stones

Because oxalate is a metabolite of vitamin C, there is some concern that high vitamin C intake could increase the risk of oxalate kidney stones. Some but not all studies have reported that supplemental vitamin C increases urinary oxalate levels. Whether any increase in oxalate levels would translate to an elevation in risk for kidney stones has been examined in epidemiological studies. Two large prospective studies, one following 45,251 men for six years and the other following 85,557 women for 14 years, reported that consumption of ≥1,500 mg of vitamin C daily did not increase the risk of kidney stone formation compared to those consuming <250 mg daily. However, a more recent prospective study that followed 45,619 men for 14 years found that those who consumed ≥1,000 mg/day of vitamin C had a 41% higher risk of kidney stones compared to men consuming <90 mg of vitamin C daily—the current recommended dietary allowance. In this study, low intakes (90-249 mg/day) of vitamin C (primarily from the diet) were also associated with a significantly elevated risk. Supplemental vitamin C intake was only weakly associated with increased risk of kidney stones in this study. Despite conflicting results, it may be prudent for individuals predisposed to oxalate kidney stone formation to avoid high-dose vitamin C supplementation.