Vitamin C supplementation

By Doreen, Pharmacist

Vitamin C or ascorbic acid, is an essential vitamin, meaning your body cannot produce it.  It is a water-soluble vitamin and cannot be stored in the body.  This means, it must be regularly supplied through diet.  Fruits and vegetables are the best food sources of vitamin C.  Eating a variety of these healthy foods will help people meet their daily requirements.  

Recommended Vitamin C Intake for Malaysian

While it is commonly advised to get your vitamin C intake from foods, many people turn to supplements to meet their needs.

Some studies have shown that Vitamin C is possibly effective for:

Common cold. Vitamin C has long been a popular remedy for cold. However, review of various studies done on vitamin C showed that there is no evidence that vitamin C supplementation is effective to prevent cold. Nevertheless, people that are taking vitamin C supplements regularly tend to have shorter duration and severity of cold. Unfortunately, using vitamin C after getting a cold does not seem to have the same effects.

Cancer. Studies shown that high intake of vitamin C from fruits and vegetables might decrease the risk of getting cancer but same effect is not observed with vitamin C supplements.

Eye disease.  Taking oral vitamin C supplements in combination with other vitamins and minerals seems to prevent age-related macular degeneration (AMD) from worsening. Some studies also suggest that people who have higher levels of vitamin C in their diets have a lower risk of developing cataracts.

Overdosage of vitamin C

Vitamin C is absorbed in the small intestine in 70-80%. It is not stored in the body, so unused amounts are excreted quickly. Therefore, there is no risk of an overdose of even with a daily intake of 1000 mg of vitamin C.

However, intake of high dose vitamin C (>2000mg) for long term are not recommended. It may cause severe side effects such as severe diarrhoea and kidney stones (that may cause kidney injury).

Food (fruits and vegetables) are the best source of vitamin C. 

• Vegetables and fruit should be consumed raw and freshly after preparation, as vitamin C is very perishable and not very resistant to high temperatures.  
• Fruits and vegetables should be eaten immediately after cutting or blended into juices to avoid oxidation.
• If your diet is poor in raw fruit and vegetables, it is worth considering supplementation to cover your daily requirement of vitamin C.

Talk to your doctor and pharmacist before taking vitamin C supplements, especially in high doses.

Do NOT take vitamin C supplements if you have:

• Recurrent kidney stone
• Renal impairment or on chronic hemodialysis
• Blood disorder (G6PDH deficiency and hemochromatosis)

References:

• Importance and toxicity of vitamin C - PORTAL MyHEALTH retrieved from http://www.myhealth.gov.my/en/importance-toxicity-vitamin-c/
• Vitamin C - Mayo Clinic retrieved from https://www.mayoclinic.org/drugs-supplements-vitamin-c/art-20363932#:~:text=Vitamin%20C%20is%20found%20in%20citrus%20fruits%2C%20berries%2C,get%20enough%20vitamin%20C%20from%20a%20healthy%20diet.
• The 11 Best Vitamin C Supplements of 2022 (healthline.com) retrieved from https://www.healthline.com/nutrition/best-vitamin-c-supplement#how-to-choose
• Vitamin C: should we supplement? - PubMed (nih.gov) retrieved from https://pubmed.ncbi.nlm.nih.gov/29864039/
• Vitamin C - Health Professional Fact Sheet (nih.gov) retrieved from https://ods.od.nih.gov/factsheets/vitaminC-HealthProfessional/