Threonic Acid Enhanced Buffered Calcium Ascorbate
Also known as: Calcium ascorbate, Threonic Acid Enhanced Buffered Calcium Ascorbate, Ester-C®, Buffered vitamin C, Vitamin C with calcium threonate, Calcium Ascorbate
Overview
Calcium ascorbate is a mineral-buffered form of vitamin C, which is less acidic than traditional ascorbic acid. This formulation is often enhanced with threonic acid, a metabolite of vitamin C, with the aim of improving its bioavailability and gastrointestinal tolerability. While not naturally abundant, this manufactured supplement combines the antioxidant and immune-supporting benefits of vitamin C with the buffering properties of calcium, making it a preferred choice for individuals sensitive to the acidity of other vitamin C forms. Its primary applications include supplementing vitamin C intake, supporting immune function, and providing antioxidant protection. The inclusion of threonic acid is purported to enhance vitamin C absorption and retention within the body, potentially leading to higher leukocyte vitamin C concentrations crucial for immune defense. Research on calcium ascorbate is moderate, with good evidence for its tolerability and ability to increase vitamin C levels, though specific benefits from threonic acid enhancement require further independent, large-scale clinical trials.
Benefits
Calcium ascorbate offers several evidence-based benefits, primarily its superior gastrointestinal tolerability compared to ascorbic acid, resulting in fewer epigastric adverse events. Systematic reviews indicate that calcium ascorbate effectively increases leukocyte vitamin C concentrations, which is vital for robust immune function. Some preliminary evidence suggests it may reduce the incidence and duration of common colds, though more research is needed to confirm these findings. Vitamin C supplementation, including buffered forms, can modestly improve endothelial function and slightly reduce serum uric acid, although the clinical significance of these effects is limited. Individuals with gastrointestinal sensitivity to ascorbic acid are the primary beneficiaries of this buffered form. While threonic acid is theorized to enhance vitamin C bioavailability, human data remain inconclusive, and direct high-quality randomized controlled trials specifically on threonic acid-enhanced formulations are limited. The benefits related to immune support and antioxidant activity are well-established for vitamin C in general, with calcium ascorbate providing a more comfortable delivery method.
How it works
Calcium ascorbate functions primarily by delivering vitamin C, a potent antioxidant and essential cofactor for numerous enzymatic reactions, including collagen synthesis. As a buffered form, it reduces the acidity typically associated with ascorbic acid, thereby minimizing gastrointestinal irritation and improving tolerability. Once absorbed, vitamin C acts to protect cells from oxidative stress by neutralizing free radicals and supports the immune system by increasing vitamin C concentrations within leukocytes (white blood cells). The calcium component contributes to bone health and cellular signaling. The proposed mechanism for threonic acid is that it may facilitate vitamin C transport or retention within the body, potentially enhancing its overall bioavailability and tissue saturation, though this specific mechanism requires more conclusive human evidence. The supplement is absorbed in the intestine, and its buffered nature aids in smoother passage through the digestive system.
Side effects
Calcium ascorbate is generally considered safe and well-tolerated at typical doses. Common side effects are mild and less frequent than with ascorbic acid, primarily involving mild gastrointestinal discomfort. At higher doses, some individuals may experience uncommon side effects such as mild diarrhea or loose stools. Allergic reactions are exceedingly rare. Regarding drug interactions, vitamin C can influence the absorption and metabolism of certain medications, such as chemotherapy agents and statins, but calcium ascorbate does not significantly alter this established profile. Contraindications include caution for individuals with hemochromatosis due to vitamin C's ability to increase iron absorption. Special populations, such as pregnant and lactating women, should adhere to recommended doses. Individuals with a history of kidney stones should monitor their vitamin C intake, as high doses might theoretically increase oxalate excretion, although this risk is generally low with typical supplementation.
Dosage
The minimum effective dose for maintaining adequate plasma vitamin C levels is generally around 200-500 mg/day. For optimal benefits, particularly for immune support or antioxidant effects, a dosage range of 500 mg to 2 grams per day is commonly used in studies. The maximum safe dose is considered to be up to 2 grams per day; doses exceeding this may increase the likelihood of gastrointestinal upset. To improve absorption and further reduce potential gastrointestinal side effects, it is often recommended to divide daily doses. Buffered calcium ascorbate is particularly recommended for individuals who experience gastrointestinal sensitivity with other forms of vitamin C. While co-ingestion with food may improve tolerability, it does not necessarily enhance absorption. No specific cofactors are required for its utilization, as a balanced diet generally supports vitamin C metabolism.
FAQs
Does threonic acid enhance vitamin C absorption?
Evidence is inconclusive; while some claims exist, independent human studies have not consistently shown a significant difference in vitamin C absorption or retention compared to ascorbic acid alone.
Is calcium ascorbate better than ascorbic acid?
Calcium ascorbate is generally better tolerated due to its buffered nature, leading to fewer gastrointestinal side effects. It also effectively increases leukocyte vitamin C concentrations, similar to ascorbic acid.
How long before effects are seen?
Leukocyte vitamin C levels can begin to increase within days of consistent supplementation. However, noticeable clinical benefits, particularly for immune function, may take several weeks of sustained use.
Is it safe to take high doses?
Doses up to 2 grams per day are generally considered safe for most individuals. Higher doses may increase the risk of mild gastrointestinal side effects like diarrhea or loose stools.
Research Sources
- https://pubmed.ncbi.nlm.nih.gov/39861409/ – This systematic literature review found that calcium ascorbate is better tolerated than ascorbic acid, with fewer gastrointestinal side effects. It also demonstrated that calcium ascorbate effectively increases leukocyte vitamin C concentrations, which is crucial for immune function, and noted potential immune benefits, though some studies were small.
- https://lpi.oregonstate.edu/mic/vitamins/vitamin-C/supplemental-forms – This source from the Linus Pauling Institute provides an overview of various supplemental forms of vitamin C, including calcium ascorbate and the concept of enhanced bioavailability with metabolites like threonic acid. It highlights that while claims exist for enhanced absorption with threonic acid, independent human data are often inconclusive.
- https://pmc.ncbi.nlm.nih.gov/articles/PMC8256468/ – This animal study investigated the effects of magnesium L-threonate and vitamin C on memory in lead-exposed mice. While it showed cognitive benefits in an animal model, the findings are not directly transferable to humans or to calcium threonate, which is a different compound.
- https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2015.4087 – This EFSA scientific opinion assesses the safety of various vitamin C forms, including calcium ascorbate. It generally supports the safety and tolerability of calcium ascorbate at typical supplemental levels, indicating no significant safety concerns with threonic acid at levels found in supplements.
- https://lpi.oregonstate.edu/mic/vitamins/vitamin-C – This comprehensive resource from the Linus Pauling Institute details the general benefits of vitamin C supplementation, including its role in improving endothelial function and modestly reducing serum uric acid. It also discusses the overall safety profile and dosage considerations for vitamin C.