Vitamin C- How much do you need and what form is best?
Vitamin C is an essential vitamin that our bodies require from food. Vitamin C or ascorbic acid is a powerful antioxidant and serves as a cofactor for other enzymes. These enzymes are involved in the biosynthesis of proteins such as L-carnitine, neuropeptides and collagen. Collagen is a major building block for connective tissue such as skin, bones and joints.
Vitamin C also can aid the absorption of certain minerals such as iron and copper; and has the ability to regenerate vitamin E [1].

This powerful vitamin is found mostly in vegetables and fruit. In Australia, approximately 40% of Vitamin C consumed, comes from vegetables. The Australian bush food Terminalia ferdinandiana (Kakadu Plum) is one of the richest sources and can have up to 2,907 mg of vitamin C, more than 100 times that of oranges [1, 2].

What form of Vitamin C is best?
It is always best to get your vitamin C from fruit and vegetables rather than supplementation because real food provides other beneficial nutrients such as flavonoids. These plant compounds may provide extra health benefits and may offer greater protection against cancers, diabetes, respiratory disease, metabolic conditions and heart disease [3,4].

However, the Vitamin C content of fresh food is often unstable and can deteriorate quickly. Vitamin C content of fruit and vegetables is affected by season, transport, storage and cooking techniques. To get the most out of you fruit and vegetables follow these tips:

  • Eat raw fruit or vegetables or steam vegetables.
  • Store in cool temperatures such as your refrigerator.
  • Buy in season and avoid buying from grocers who store fruit and vegetables for months in cool rooms.
  • Buy local food from Farmers markets, which sell fresh produce that is in season.
Although natural sources of vitamin C are better, due to the synergy of other potent plant compounds, natural and synthetic forms of vitamin C are bioidentical. Vitamin C supplements are available in many forms. To date there is no evidence that one form is better absorbed than another [3]. However, buffered forms such as mineral salts (mineral ascorbates) are less acidic and may be best for people who have gastrointestinal issues. Ascorbyl palmitate is frequently used in topical treatments to promote collagen synthesis and is often marketed as vitamin C ester [3].

How Much Vitamin C Do I Need?

Ascorbic acid is water soluble and dose dependent. It is best absorbed through the day rather than one large dose [1]. The body can absorb up to 200 mg at a time through the gastrointestinal tract, the excess is excreted in the urine [3].
Higher amounts can be retained by the body through IV transfusion. High dose IV vitamin C can safely be used to treat symptoms of ascorbate deficiency, particularly in people who can not absorb vitamin C due to chronic disease and may help to reduce inflammation [5].

A body pool of less than 300-400 mg is associated with the symptoms of scurvy, which can occur within 1-3 months of depletion [1, 5]. Scurvy is a nasty disease which, is characterised by tooth loss, gum disease, bleeding sores under the skin, fatigue, anaemia, and poor wound healing. If left untreated, it could lead to possible death.

The estimates of vitamin C requirements made by the Australian Government are based on prevention of scurvy and some vitamin C studies [1]. The recommended daily intake of vitamin C is as follows:

Adult women and men: 45 mg/day.
Pregnant women 60 mg/day
Breast feeding: 80mg/day.

Global recommended daily intakes (RDI) for vitamin C can vary, RDA criteria in some countries, was based on prevention of scurvy and not optimisation of health. According to a review on RDI recommendations by A dose of >200 mg/d is considered safe and the benefits seem to outweigh suboptimal consumption. An intake of 200 mg/d can be obtained from a diet of 5 or more veg & fruit servings [6].

It is not possible to establish an upper limit (UL), but 1,000 mg/day is prudent. There does not seem to be any adverse effects and no toxicity.

Some people might experience gastrointestinal disturbances such as diarrhoea with an upper intake of 2 grams per day. Those predisposed to kidney stones may consider avoiding high doses of supplementation [3].

Groups at Risk of Vitamin C inadequacy

Smokers and passive smokers need more vitamin C due to higher metabolism and require up to 35 mg more vitamin C per day than non-smokers; It was found that plasma vitamin C concentrations are reduced by 40% in male smokers [1].

Those that have a very limited variety of food intake due to illness, fad diets, lack of appetite, and/or are picky eaters will most likely require supplementation as with people with malabsorption and chronic disease [6].

There is a correlation between Vitamin C status and bodyweight, with higher weight associated with suboptimal vitamin C status. It is proposed that recommended vitamin C intakes should be based on dose per kilo body weight [7]. Some research indicates that low vitamin C status may also hinder fat burning mechanisms [8].

Prevention of Flu, Virus and Common Cold
Vitamin supplementation has shown to modestly reduce the duration and severity of the common colds. Some trials showed duration of colds was reduced to 8% in adults and 14% in children [6,9,10]. Supplementation on athletes or people under severe physical stress seemed to respond better to vitamin C supplementation than athletes who did not take supplements [8] and were able to reduce symptoms by almost half.
For people who do not consume fruit and vegetables, a small daily dose of 1.0g/day is recommended and a dose of 3.0/day- 4.0g/day at the onset of cold or flu symptoms [9].
References:

1 Nutrient Reference Values for Australia and New Zealand, Vitamin C,
Australian Government [internet]. 2017 [cited May 2020]; Available from: https://www.nrv.gov.au/nutrients/vitamin-c

2 Fruitsinfo.com. Kakadu plum. [internet].2020 [cited May 2020]; Available from:
http://www.fruitsinfo.com/kakadu-plum.php#Nutritional-Value

3 Oregon State University, Vitamin C, Linus Pauling Institute,
[internet]. 2020 {cited May 2020];
Available from: https://lpi.oregonstate.edu/mic/vitamins/vitamin-C

4 Hunter DC, Skinner MA, Wolber FM, et al. Consumption of gold kiwifruit reduces severity and duration of selected upper respiratory tract infection symptoms and increases plasma vitamin C concentration in healthy older adults. Br J Nutr. [internet]. 2012 [cited May 2020];108(7):1235‐1245.
Available from: https://pubmed.ncbi.nlm.nih.gov/22172428/

5 Klimant E, Wright H, Rubin D, Seely D, Markman M. Intravenous vitamin C in the supportive care of cancer patients: a review and rational approach. Curr Oncol. [internet]. 2018 [cited May 2020];25(2):139‐148. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5927785/

6 National Institutes of Health, Vitamin C fact Sheet for Professionals, USA.gov [internet]. 2020 [cited May 2020]; Available from:
https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

7 Carr AC and Lykkesfeldt J. Discrepancies in global vitamin C recommendations: a review of RDA criteria and underlying health perspectives, Critical Reviews in Food Science and Nutrition [internet]. 2020 [cited May 2020]; Available from:
https://www.tandfonline.com/doi/full/10.1080/10408398.2020.1744513

8 Johnston CS, Corte C, Swan PD. Marginal vitamin C status is associated with reduced fat oxidation during submaximal exercise in young adults. Nutrition and Metabolism [internet]. 2006 [cited May 2020]; 3 (35). Available from: https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-3-35

9 Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systemic Reviews [internet]. 2013 {cited May 2020];1 Available from: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD000980.pub4/epdf/full

10 Ran L, Zhao W, Wang J, et al. Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials. Biomed Res Int. [internet].2018 [cited May 2020]; Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6057395/