How Is Vitamin C Best Absorbed
• Vitamin C is an essential nutrient for many aspects of health including your immune system
• Your body uses extra vitamin C during times of increased need such as illness or infection so unless extra care is taken to increase dietary intake during these times, daily supplies are likely to fall short. This is when supplemental vitamin C may be a useful addition to your diet.
• Ascorbic acid is the form of vitamin C found naturally in food. It has good bioavailability but some people find it too acidic on their gut and can't tolerate higher doses.
• Bioflavonoids are beneficial plant compounds often added to vitamin C supplements. They deliver extra immune benefits and may help to increase bioavailability.
• Mineral ascorbates such as calcium and magnesium ascorbate are often called 'buffered' vitamin C. Many people find these to be gentler forms of vitamin C that are better tolerated by the gut. It is important however to consider the accompanying dose of mineral (calcium, magnesium etc.) when taking higher levels.
• Time-release vitamin C is often the preferred choice since vitamin C has better bioavailability when taken in smaller doses throughout the day. A time-release formula aims to solve this problem without taking multiple tablets, by releasing the vitamin C slowly throughout the day.
• Ester-C® is a patented form of buffered vitamin C (mainly calcium ascorbate) that has been shown to be well absorbed and tolerated in the gut like other mineral ascorbates.
Vitamin C - A powerful immune-support nutrient
The health benefits of vitamin C are well documented. Vitamin C is an essential nutrient for many aspects of your everyday health, and more recently its powerful immune-supportive roles have been hitting the headlines.
Why do we need extra vitamin C?
"An inadequate vitamin C intake is already more widespread than many people realize."3
Humans are in a small minority of mammals that can't produce their own vitamin C; it's also water soluble and can't be stored in the body. This means it must be regularly supplied by the diet.1 Severe deficiency leading to scurvy is rare in the developed world,2 but there are times when our daily needs for vitamin C are likely to increase, such as pollution exposure and during times of chronic stress, illness and infection.3
Learn More
• SUPPLEMENTS: Vitamin C Range
• MORE DETAIL: Taking A Closer Look At Vitamin C
• FACTS: Vitamin C Facts & Health Benefits
What the science says:
In a 2020 review article on the role of micronutrients in the immune system, the authors explain,
"The body may lose micronutrients when exposed to pathogens, which causes the immune system to become increasingly active. The loss is exacerbated during an active infection (including vitamins A, C, and E, calcium, zinc, and iron), and plasma levels only return to normal once symptoms improve. An adequate micronutrient intake is essential to aid recovery from infection, made more difficult by the fact that food intake may decrease during illness, and that antibiotic use can also deplete certain micronutrients.
For example, levels of vitamin C in plasma rapidly fall to half their original concentration during an infection, to levels indicative of a suboptimal status with a risk of deficiency (i.e., ≤50 μmol/L).
However, the high intake of vitamin C required to counteract the fall in concentration after infection (gram doses), or even simply to help reduce the risk of infection…/… may be difficult to achieve when the data show that people already often fail to reach the current RDA for vitamin C (25–90 mg/day), depending on age, and that an inadequate vitamin C intake is already more widespread than many people realize."3
Adding a bit more vitamin C when we need it most sounds simple enough, however there are so many different supplements on the market, it's easy to feel confused about which is the best to take. Here we take a look at the different types, to help you decide what's right for you.
Different forms of vitamin C
Ascorbic acid
Most food supplements contain vitamin C in the form of ascorbic acid. This is the proper name for vitamin C and the form found naturally in foods. Synthetic ascorbic acid found in supplements has been found to have similar bioavailability to that of naturally occurring ascorbic acid in foods, such as broccoli and citrus fruit (it is important to note however that whilst synthetic and food-derived vitamin C are chemically identical, the vitamin C in fruits and vegetables is packaged up with various additional nutrients and phytonutrients which may influence its health benefits and how it is used by the body). Research to date also seems to suggest that the bioavailability of ascorbic acid appears to be the same whether it is given in powder or tablet form. 4-12
Some people find however that vitamin C given in the supplemental form of ascorbic acid upsets their stomach, and may better tolerate different forms that are gentler on the gut,13 or time-release versions which release the vitamin C more slowly and may also reduce the risk of gastrointestinal upset.
Vitamin C with bioflavonoids
Bioflavonoids (or flavonoids) are polyphenolic compounds found in plants, and are especially plentiful in vitamin C-rich plant foods. There are around 5,000 different varieties of flavonoids and they are made by plants in response to microbial infection. You will often find vitamin C and bioflavonoids together in a synergistic supplement formula. This is because some research has found that the addition of flavonoids may help to increase the absorption of vitamin C from supplements; other studies however have found there to be no difference.14-19
Aside from the possible benefits of increasing bioavailability of vitamin C however, flavonoids have demonstrated significant health benefits in their own right. In plants, flavonoids help to reduce harmful oxidative stress and regulate growth. And when flavonoids are consumed in the diet they have been shown to have significant antioxidant and free radical scavenging abilities. In addition, they have demonstrated anti-inflammatory activity and offer cardiovascular, metabolic, neuroprotective, anti-cancer, hepatoprotective, potential anti-viral benefits and more.20,21
Mineral ascorbates
Also commonly referred to as 'buffered' vitamin C, mineral salts (mineral ascorbates) are less acidic and are often recommended to people who are sensitive to acidic foods. Whilst there is only limited scientific evidence to support this claim,13 anecdotal reports are that mineral ascorbates ('buffered' vitamin C) are often better tolerated.
Most common mineral ascorbates include sodium ascorbate, calcium ascorbate, potassium ascorbate and magnesium ascorbate. It is important to note however that both the ascorbic acid and the mineral are typically well absorbed so the dose of the accompanying mineral needs to be taken into account alongside the ascorbic acid, especially when taking a higher dosage.22
Time-release vitamin C
Research has found that single doses of vitamin C greater than 200 mg have lower relative bioavailability, indicating that taking several smaller doses through the day may be more effective than a single large dose. Time-release versions aim to solve this problem by releasing the vitamin C more slowly throughout the day. A number of studies have also evaluated the relative bioavailability of vitamin C from different tablet formulations and found that slow-release versions provide improved vitamin bioavailability.23-27
Ester-C
This is a patented form of vitamin C which contains mainly calcium ascorbate (buffered vitamin C). Animal studies have found Ester-C®to be better absorbed and excreted less rapidly than ascorbic acid and to have superior anti-scorbutic (scurvy-preventing) activity. These results haven't as yet been replicated in humans.28-30 Ester-C® has, however, been found to be better tolerated in a small human study on people who are sensitive to acidic foods. In a 2006 randomised, double-blind crossover clinical trial published in Advances in Therapy, researchers evaluated whether Ester-C® calcium ascorbate causes fewer epigastric adverse effects than regular ascorbic acid in 50 healthy volunteers sensitive to acidic foods. Researchers concluded that compared with ascorbic acid, Ester-C® caused significantly fewer epigastric adverse effects in participants who are sensitive to acidic foods and that Ester-C® is much better tolerated.31
Depending on your vitamin C needs you can choose:
✔ Ascorbic acid or gentle buffered form
✔ Combined with added ingredients such as bioflavonoids to provide synergistic support, and which may also enhance bioavailability
✔ Timed-release form
At Nutri Advanced we believe that no matter what your choice, a formula should always be:
✔ Research-backed
✔ Free from fillers, refined sugar, artificial sweeteners or colourings
✔ Hypo-allergenic
✔ Clinically-relevant dosage
✔ Allow for flexible dosing
References:
1. Frei B., Birlouez-Aragon I., Lykkesfeldt J. Authors' perspective: What is the optimum intake of vitamin C in humans? Crit. Rev. Food Sci. Nutr. 2012; 52: 815 – 829
2. Na IS, Nguyen K et al. Now you C me: a case of scurvy presenting as depression and anaemia. BMJ Case Rep. 2020 Mar 4; 13(3)
3. Gombart AF, Pierre A et al. A review of micronutrients and the immune system – Working in harmony to reduce the risk of infection. Nutrients 2020 Jan; 12(1): 236
4. Bates CJ. Bioavailability of vitamin C. Eur J Clin Nutr 1997;51 (Suppl 1): S28-33
5. Mangels AR, Block G, et al. The bioavailability to humans of ascorbic acid from oranges, orange juice and cooked broccoli is similar to that of synthetic ascorbic acid. J Nutr 1993; 123:1054-61
6. Gregory JF 3rd. Ascorbic acid bioavailability in foods and supplements. Nutr Rev 1993; 51: 301-3.
7. Yung, S. et al. Ascorbic acid absorption in humans: a comparison among several dosage forms. Journal of Pharmaceutical Sciences. 1982; volume 71: pages 282-285.
8. Kondo Y., Higashi C., et al. Bioavailability of vitamin C from mashed potatoes and potato chips after oral administration in healthy Japanese men. Br. J. Nutr. 2012; 107: 885–892.
9. Uchida E., Kondo Y., et al. Absorption and excretion of ascorbic acid alone and in acerola (Malpighia emarginata) juice: Comparison in healthy Japanese subjects. Biol. Pharm. Bull. 2011; 34:1744 – 1747.
10. Carter B., Monsivais P., Drewnowski A. Absorption of folic acid and ascorbic acid from nutrient comparable beverages. J. Food Sci. 2010;75:H289–H293.
11. Guarnieri S., Riso P., Porrini M. Orange juice vs vitamin C: Effect on hydrogen peroxide-induced DNA damage in mononuclear blood cells. Br. J. Nutr. 2007; 97:639–643.
12. Nelson E.W., Streiff R.R., Cerda J.J. Comparative bioavailability of folate and vitamin C from a synthetic and a natural source. Am J Clin Nutr. 1975; 28: 1014–1019.
13. Gruenwald J, Graubaum HJ et al. Safety and tolerance of Ester-C® compared with regular ascorbic acid. Adv Ther. 2006 Jan-Feb; 23(1): 171-8
14. Vinson, J.A. & Bose, P. Comparative bioavailability to humans of ascorbic acid alone or in a citrus extract. American Journal of Clinical Nutrition. 1988; volume 48: pages 501-604
15. Carr AC, Vissers MC. Synthetic or food-derived vitamin C-are they equally bioavailable? Nutrients. 2013;5(11):4284-4304.
16. Uchida E, Kondo Y, et al. Absorption and excretion of ascorbic acid alone and in acerola (Malpighia emarginata) juice: comparison in healthy Japanese subjects. Biol Pharm Bull. 2011;34(11):1744-1747.
17. Carr AC, Bozonet SM, et al. A randomized steady-state bioavailability study of synthetic versus natural (kiwifruit-derived) vitamin C. Nutrients. 2013; 5(9): 3684-3695.
18. Jones E, Hughes RE. The influence of bioflavonoids on the absorption of vitamin C. IRCS Med Sci. 1984; 12: 320.
19. Johnston, C.S. & Luo, B. Comparison of the absorption and excretion of three commercially available sources of vitamin C. Journal of the American Dietetic Association. 1994; volume 94: pages 779-781.
20. Kumar S, Pandey AK. Chemistry and biological activities of flavonoids: an overview. The Scientific World Journal. 29 Dec 2013. Article ID 162750
21. https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids#figure-4
22. https://lpi.oregonstate.edu/mic/vitamins/vitamin-C/supplemental-forms#reference7
23. Levine M., Conry-Cantilena C., et al. Vitamin C pharmacokinetics in healthy volunteers: Evidence for a recommended dietary allowance. Proc. Natl. Acad. Sci. USA. 1996; 93: 3704–3709.
24. Yung S., Mayersohn M., Robinson J.B. Ascorbic acid absorption in humans: A comparison among several dosage forms. J. Pharm. Sci. 1982; 71: 282–285.
25. Bhagavan H.N., Wolkoff B.I. Correlation between the disintegration time and the bioavailability of vitamin C tablets. Pharm. Res. 1993; 10: 239–242.
26. Sacharin R., Taylor T., et al. Blood levels and bioavailability of ascorbic acid after administration of a sustained-release formulation to humans. Int. J. Vitam. Nutr. Res. 1977; 47: 68–74.
27. Nyyssonen K., Poulsen H.E., et al. Effect of supplementation of smoking men with plain or slow release ascorbic acid on lipoprotein oxidation. Eur. J. Clin. Nutr. 1997; 51:154–163.
28. Bush M.J., Verlangieri A.J. An acute study on the relative gastro-intestinal absorption of a novel form of calcium ascorbate. Res. Commun. Chem. Pathol. Pharmacol. 1987; 57: 137–140.
29. Verlangieri A.J., Fay M.J., Bannon A.W. Comparison of the anti-scorbutic activity of L-ascorbic acid and Ester C® in the non-ascorbate synthesizing Osteogenic Disorder Shionogi (ODS) rat. Life Sci. 1991; 48: 2275–2281.
30. Johnston C.S., Luo B. Comparison of the absorption and excretion of three commercially available sources of vitamin C. J. Am. Diet. Assoc. 1994; 94:779–781.
31. Gruenwald J, Graubaum HJ et al. Safety and tolerance of Ester-C® compared with regular ascorbic acid. Adv Ther. 2006 Jan-Feb; 23(1): 171-8
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How Is Vitamin C Best Absorbed
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