Why do we need vitamin C?
Vitamin C, or ascorbic acid, so well known yet often overlooked vital nutrient -
- is critical for our immune system, and, for example, decreases symptoms of the common cold (Franz, 1956; Arminio, 1956);
- is a powerful anti-oxidant on its own and a helper to other anti-oxidants, e.g. vitamin E;
- participates in the synthesis of collagen (think - younger skin, ligaments, bones, tendons),
- participates in the synthesis of carnitine, which is necessary for the energy production in mitochondri; one study showed that high dose IV vitamin C significantly reduced fatigue (Suh, 2012);
- participates in the synthesis of catecholamines (hormones made by the adrenal glands);
- helps absorbing iron;
- may decrease the risk of coronary heart disease: a meta-analysis of 9 studied concluded that a daily intake of more than 700 mg of supplemental vitamin C per day was associated with a slightly lower incidence of coronary heart disease (Knekt P, 2004).
Humans are among very few species whose bodies cannot synthesize ascorbic acid; therefore we need to receive it from either food sources or as a supplement. Cats and dogs, for example, make their own ascorbic acid, and so it is not a vitamin (not a vital nutrient) to them.
What is the best dose? Daily intake recommendations
Vitamin C is water soluble; it means that if you take an excessive amount, your body is going to flush it out with urine; it will not be stored in the body. It also means that vitamin C needs to be consumed daily; even better two or three times a day.
Official health recommendations say to limit vitamin C to 2,000 mg a day because of the possible diarrhea, heartburn, headache. However, there is no scientific evidence that vitamin C is toxic or has negative impacts on health in the doses of up to 10,000 mg a day.
The daily 40 - 100 mg of vitamin C recommended by health authorities of many countries, including USA, Canada, Russia, Australia, Germany is the amount necessary to not fall a victim of scurvy. It is definitely NOT the dose sufficient for your body's numerous metabolical processes where vitamin C is involved, and not sufficient to be healthy and to function effectively. Somewhat recently, at least the Upper Limit intake has been increased by FDA to 2,000 mg (2 g) a day.
What numbers do we have?
I personally take 1 gram (1,000 mg) twice a day and increase the dose 2-3 times when I have a cold or a flu. If you prefer to go purely by scientific studies conducted to date, then it's 400 mg a day except for elderly and smokers - some 500-600 mg/day then.
Official health recommendations say to limit vitamin C to 2,000 mg a day because of the possible diarrhea, heartburn, headache. However, there is no scientific evidence that vitamin C is toxic or has negative impacts on health in the doses of up to 10,000 mg a day.
The daily 40 - 100 mg of vitamin C recommended by health authorities of many countries, including USA, Canada, Russia, Australia, Germany is the amount necessary to not fall a victim of scurvy. It is definitely NOT the dose sufficient for your body's numerous metabolical processes where vitamin C is involved, and not sufficient to be healthy and to function effectively. Somewhat recently, at least the Upper Limit intake has been increased by FDA to 2,000 mg (2 g) a day.
What numbers do we have?
- Vitamin C from food sources is regarded as safe regardless of the dose;
- Official health recommendations in the USA say to limit vitamin C to 2,000 mg a day because of the possible diarrhea, heartburn, headache. However, there is no scientific evidence that vitamin C is toxic or has a negative impact on health in the doses of up to 10,000 mg a day;
- There were several studies on whether high intake of vitamin C may increase the risk of oxalate kidney stone formation (Thomas, 2013). Study results are contradictory and inconclusive. Having said that, for men prone to the formation of oxalate kidney stones it may be better to not take more than 1,000 mg of vitamin C a day;
- Studies by the National Institutes of Health showed that young subjects had near-maximal concentrations of vitamin C at a dose of 400 mg/day (Frei, 2012);
- One study showed that elderly (over 60 years) and smokers need at least 25% - 50% more vitamin C than younger people and non-smokers do (Brubacher, 2000);
- A Nobel prize laureate Linus Pauling was an advocate of vitamin C mega-dosing. He estimated that if humans, like majority of mammals, produced their own vitamin C, it would be some 15,000 - 20,000 mg a day. He recommended taking 2,000 to 18,000 mg daily.
I personally take 1 gram (1,000 mg) twice a day and increase the dose 2-3 times when I have a cold or a flu. If you prefer to go purely by scientific studies conducted to date, then it's 400 mg a day except for elderly and smokers - some 500-600 mg/day then.
What form of vitamin C is better?
- Generally speaking, natural is almost always better, and if you are comfortable with the numbers from the studies (400-600 mg a day), you should be able to obtain that dose of vitamin C from fruits and vegetables.
- Vitamin C occurs naturally as L-ascorbic acid. Natural L-ascorbic acid (e.g. in an orange) is exactly the same compound as L-ascorbic acid in supplements; and in humans there are no differences in absorption or bioavailability (Gregory JF, 1993);
- If you are sensitive to the acidity of the ascorbic acid, there are salt (buffered) forms of the vitamin C: sodium ascorbate and calcium ascorbate and also a liposomal vitamin C, which may also have a better bioavailability.
With or without bioflavonoids?
Bioflavonoids or flavonoids are plant pigments that have their own health benefits.
Two of the most studied bioflavonoids occurring in citrus fruits along with vitamin C are rutin and hesperdin. They are anti-oxidants with other health benefits of their own; they may be working synergistically with vitamin C.
- One study showed that vitamin C in orange juice may protect against oxidative DNA damage better than the isolated ascorbic acid (Carr, 2013). We could speculate that the reason is in a synergetic work of vitamin C with other natural compounds, e.g., bioflavonoids; however, that has not been established;
- A review of 10 studies showed no or minimal impact of bioflavonoids on the bioavailability of vitamin C (Carr, 2013). However, the same bioavailability does not necessarily translate into the same health impact;
- A lately popular flavonoid quercetin: in rat studies, quercetin decreases absorption of vitamin C (Song, 2002); it is not known whether it is the same for humans.
Supplements that look good to me
If you are taking a vitamin C supplement instead of or in addition to the food sources, and your budget for vitamin C is limited or you want to get the best value for your money, get the least expensive product you can find, because ascorbic acid is ascorbic acid. Bulk powder of L-ascorbic acid is going to be the best value.
However, if you are willing to pay for "just in case it may be better for me", which is what I am doing, then consider taking ascorbic acid together with bioflavonoids, including hesperdin and rutin. In the table below, I included the supplements that I pre-selected for my personal use )I am happy with the L-ascorbic acid form and have not considered the liposome or buffered (salt) form of the vitamin)).
However, if you are willing to pay for "just in case it may be better for me", which is what I am doing, then consider taking ascorbic acid together with bioflavonoids, including hesperdin and rutin. In the table below, I included the supplements that I pre-selected for my personal use )I am happy with the L-ascorbic acid form and have not considered the liposome or buffered (salt) form of the vitamin)).
Brand and supplement |
Form, capsules per bottle |
Vitamin C per 1 |
Bioflavonoids |
Incl. Hesperdin |
Rutin |
Other ingredients |
Vital Nutrients Vitamin C with Bioflavonoids |
Capsules, 220 |
500 mg |
250 mg |
? |
? |
Gelatin capsule, rice powder, leucine |
Country Life Maxi-C |
Capsules, 90/180 |
1000 mg |
100 mg |
3 mg |
50 mg |
Cellulose, gelatin capsule, stearic acid, magnesium stearate, silica, calcium silicate |
Twinlab C-Plus with Citrus Bioflavonoids |
Capsules, 100 |
500 mg |
~ 325 |
? |
50 |
Gelatin, purified water, medium chain triglycerides, vegetable based stearic acid, silica |
Bluebonnet Vitamin C 1000 mg plus Bioflavonoids |
caplets, 180 |
1000 mg |
500 |
125 |
100 |
Vegetable cellulose, calcium phosphate, silica, stearic acid, vegetable magnesium stearate, vegetable glaze. |
? - the value was not specified on the supplement label
References and Literature
Arminio J.J., Johnston J.H., Tebrock H.E. Usefulness of bioflavonoids and ascorbic acid in treatment of common cold. J. Am. Med. Assoc. 1956;162:1227–1233.
Brubacher D, Moser U, Jordan P. Vitamin C concentrations in plasma as a function of intake: a meta-analysis. Int J Vitam Nutr Res. 2000;70(5):226-237.
https://www.ncbi.nlm.nih.gov/pubmed/11068703
Franz WL, Heyl HL, Sands GW. Blood ascorbic acid level in bioflavonoid and ascorbic acid therapy of common cold.
J Am Med Assoc. 1956 Nov 24; 162(13):1224-6.
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(9):815-829.
https://www.tandfonline.com/doi/abs/10.1080/10408398.2011.649149
Gregory JF, 3rd. Ascorbic acid bioavailability in foods and supplements. Nutr Rev. 1993;51(10):301-303.
https://www.ncbi.nlm.nih.gov/pubmed/8302486
Knekt P, Ritz J, Pereira MA, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. Am J Clin Nutr. 2004;80(6):1508-1520.
https://www.ncbi.nlm.nih.gov/pubmed/15585762
Naidu KA. Vitamin C in human health and disease is still a mystery? An overview. Nutr J. 2003;2:7. Published 2003 Aug 21. doi:10.1186/1475-2891-2-7
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC201008/
Song J, Kwon O, Chen S, et al. Flavonoid inhibition of sodium-dependent vitamin C transporter 1 (SVCT1) and glucose transporter isoform 2 (GLUT2), intestinal transporters for vitamin C and Glucose. J Biol Chem. 2002;277(18):15252-15260.
http://www.jbc.org/content/277/18/15252.long
Suh SY, Bae WK, Ahn HY, Choi SE, Jung GC, Yeom CH. Intravenous vitamin C administration reduces fatigue in office workers: a double-blind randomized controlled trial. Nutr J. 2012;11:7. Published 2012 Jan 20. doi:10.1186/1475-2891-11-7
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3273429/
Thomas LD, Elinder CG, Tiselius HG, Wolk A, Akesson A. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Intern Med. 2013;173(5):386-388.
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/1568519
Brubacher D, Moser U, Jordan P. Vitamin C concentrations in plasma as a function of intake: a meta-analysis. Int J Vitam Nutr Res. 2000;70(5):226-237.
https://www.ncbi.nlm.nih.gov/pubmed/11068703
Franz WL, Heyl HL, Sands GW. Blood ascorbic acid level in bioflavonoid and ascorbic acid therapy of common cold.
J Am Med Assoc. 1956 Nov 24; 162(13):1224-6.
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(9):815-829.
https://www.tandfonline.com/doi/abs/10.1080/10408398.2011.649149
Gregory JF, 3rd. Ascorbic acid bioavailability in foods and supplements. Nutr Rev. 1993;51(10):301-303.
https://www.ncbi.nlm.nih.gov/pubmed/8302486
Knekt P, Ritz J, Pereira MA, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. Am J Clin Nutr. 2004;80(6):1508-1520.
https://www.ncbi.nlm.nih.gov/pubmed/15585762
Naidu KA. Vitamin C in human health and disease is still a mystery? An overview. Nutr J. 2003;2:7. Published 2003 Aug 21. doi:10.1186/1475-2891-2-7
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC201008/
Song J, Kwon O, Chen S, et al. Flavonoid inhibition of sodium-dependent vitamin C transporter 1 (SVCT1) and glucose transporter isoform 2 (GLUT2), intestinal transporters for vitamin C and Glucose. J Biol Chem. 2002;277(18):15252-15260.
http://www.jbc.org/content/277/18/15252.long
Suh SY, Bae WK, Ahn HY, Choi SE, Jung GC, Yeom CH. Intravenous vitamin C administration reduces fatigue in office workers: a double-blind randomized controlled trial. Nutr J. 2012;11:7. Published 2012 Jan 20. doi:10.1186/1475-2891-11-7
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3273429/
Thomas LD, Elinder CG, Tiselius HG, Wolk A, Akesson A. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Intern Med. 2013;173(5):386-388.
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/1568519