Vitamin C: Three Things To Know
Vitamin C or ascorbic acid is an essential vitamin for body functioning, and because humans cannot synthesize it(1), our main source of Vitamin C is food. Vitamin C pills are also a source of the vitamin and contain either vitamin C alone or in combination with other vitamins and elements. While the deficiency of vitamin C is very rare (because low doses are generally sufficient to prevent it), the optimal dose that improves the wellbeing of humans is yet to be determined. What is true about the vitamin C effect? And what are the risks of high dose’s intake? Here are three take home notes.
Daily needed dose versus high doses
According to the Institute Of Medicine: The daily recommended dose (RDA) of vitamin c for a healthy adult is
- 90 mg for men (provided by approximately ¾ cup of fresh orange juice)
- 75 mg for women (provided by a medium orange)(2)
You may need higher doses of ascorbic acid (under medical supervision!) if you are Pregnant/nursing, smoker, having a vitamin C deficiency, or severely burned.(3)
In the market, you can find vitamin c in:
- Multivitamin pills: in combination with other vitamins, in general the dose of vitamin c in these pills is near the RDA.
- Alone: commonly in form of effervescent tablets of 500 to one gram.
People frequently consume vitamin C supplements during flu season because they commonly believe that it will prevent the disease, or reduce its duration and severity. In fact studies showed that taking vitamin C before the onset of symptoms didn’t prevent the disease but it shortened the duration and the severity of symptoms. However taking vitamin C after the onset of symptoms had no effect on the disease. In addition studies have failed to prove the benefits of vitamin C, when taking alone, on cancer treatment and prevention, and on cardiovascular diseases.(1)
high doses side effect
Maximum daily dose should not exceed 2g (2000mg) per day. Vitamin C supplementation is generally safe. However taking high doses for a long duration may cause more serious side effects like kidney stones and hemolysis (destruction of red blood cells).
Kidney stones: Vitamin C is metabolized to an inactive component called oxalate that is eliminated by the kidneys. High quantities of oxalate can precipitate in the urine to form calcium oxalate stones. In addition, unchanged excreted ascorbic acid can acidify the urine thus facilitate the precipitation of oxalate, urate and other components leading also to kidney stones. Some people have an increased risk for kidney stones including: patients with renal impairment, who have history of oxalate kidney stones, elderly patients and young children (less than 2 years of age)(3)
Hemolysis: high doses of vitamin C were reported to cause hemolysis in patients who have the G6PD deficiency. That’s because high doses of vitamin c increase the oxidative stress, and red blood cells are incapable of fighting high level of oxidative stress when the G6PD is deficient. In this case destruction of red blood cells occurs. Your health care professional may decrease and even discontinue your vitamin C supplements if you have the G6PD deficiency.(3)
Note: high doses of vitamin C may interfere with some laboratory test. Let your doctor know that you are taking vitamin C high doses.
vitamin c administration
Vitamin C is a highly water soluble vitamin and has a high cell permeability. Which means that it is readily absorbed and its availability to the body is not affected by food. In fact good water solubility is a condition for all molecules to be absorbed in the body because body fluids including the digestive ones are watery in nature, while good cell permeability is a must for the drugs to pass through different cell membranes(4). In conclusion vitamin c supplements could be taken without regard to food. However you may be advised by your pharmacist, doctor or by the instructions on your vitamin jar to take your pills with meals preferably. This is because the multivitamin pills contain other vitamins and components that might be affected by food like vitamin D.
Remember that vitamin C increases the absorption of iron and could be found in combination with iron pills, in this case you better take your supplement on empty stomach, one hour before or two hours after a meal.
Your Pharmacist Advice: Take the vitamin C pills without regard to meal. Take the multivitamin pills that contain Vitamin C with food.
References
1. Office of Dietary Supplements – Vitamin C [Internet]. [cited 2022 Aug 13]. Available from: https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
2. Vitamin C | The Nutrition Source | Harvard T.H. Chan School of Public Health [Internet]. [cited 2022 Aug 12]. Available from: https://www.hsph.harvard.edu/nutritionsource/vitamin-c/
3. Drug Result Page – In-Depth Answers – Medication Safety – Adverse Effects [Internet]. [cited 2022 Aug 12]. Available from: https://www.micromedexsolutions.com/micromedex2/librarian/CS/9E60E9/ND_PR/evidencexpert/ND_P/evidencexpert/DUPLICATIONSHIELDSYNC/88DD1A/ND_PG/evidencexpert/ND_B/evidencexpert/ND_AppProduct/evidencexpert/ND_T/evidencexpert/PFActionId/evidencexpert.DoIntegratedSearch?SearchTerm=vitamin%20c&UserSearchTerm=vitamin%20c&SearchFilter=filterNone&navitem=searchALL#
4. Cheng L, Wong H. Food Effects on Oral Drug Absorption: Application of Physiologically-Based Pharmacokinetic Modeling as a Predictive Tool. Pharmaceutics. 2020 Jul 17;12(7):E672.