Vitamin C: Immune System Benefits, Liposomal vs Other Forms, and Dosage for Cold Prevention.

It's that time of year where mandarins are plentiful and the vitamin C rich fruit are everywhere. Mother nature is just subtly reminding us of an important ally during winter.

Vitamin C is also known as ascorbic acid and is widely recognised as a potent antioxidant that also enhances our immune system. It is found in many areas of the body. I was surprised by the fact that the largest amount of vitamin C is actually found in the brain (1). Specifically in the hippocampus and the frontal cortex regions. Areas that are responsible for memory consolidation, decision making, and executive function such as planning. Vitamin C is retained in the brain at the expense of other tissues during times of deficiency, evidence suggests that this is important as vitamin C helps to preserve cognitive function. It also has many other physiological functions including synthesis of collagen, neurotransmitters and much more. In this article we will focus on its immune system benefits. 

What role dose vitamin C play in my immune system?

The vitamin C we consume is crucial for our immune function. It supports the production of white blood cells in particular neutrophils. Neutrophils scan the body for infection and are first to the scene of invasion. Neutrophils infiltrate the infected tissue and engulf the pathogens (2). When they do this they produce a large amount of reactive oxygen species (ROS). Vitamin C increases the antioxidant defenses of neutrophils and other immune cells such as lymphocytes and phagocytes (2). It protects neutrophils from the damage that can occur when they engulf pathogens, allows them to keep engulfing invaders for longer periods of time and supports the cells normal function such as their ability to detect infection. 

Vitamin C also plays a role in interferon production. Immune cells release interferon. Interferons are a group of proteins released as a defensive response to viruses. Some evidence shows Vitamin C may promote the production of interferon (3). 

How much vitamin C should I take a day? 

Vitamin C deficiency is known as Scurvy. Although much rarer now, in the pre modern world this was common among sailors who were at sea and without fresh produce for a long time. For years the recommended daily amount of vitamin C was recommended to prevent deficiency (4). Which begs the question how much vitamin C is important for optimal health? Currently the RDI for vitamin C is 45mg per day for adult women and 45mg per day for adult men (5). This changes in pregnancy where needs are higher increasing to 60mg and in lactation it increases to 85mg. The RDI varies for children slightly. 45mg is equivalent to about one orange. Many leading researchers argue that the optimal daily dose is much higher. 

Researchers have asked the body how much can it absorb on a daily basis. They found that the bioavailability of vitamin C is 100% of a 200mg dose (6). Above this amount the absorption declines. This indicates that the intestinal vitamin C transport mechanism has fully evolved to absorb up to about 200mg at one time (6). So if you are someone that thinks more is better and is taking 1000mg oral vitamin C or more a day in a single dose, your body is most likely excreting a large amount of this. Can we get 200mg from our food? Yes quite easily this is about five servings of fresh fruit and vegetables per day. 

How much Vitamin C do I take if I am trying to prevent the common cold?

The common cold is a viral infection of the upper respiratory tract. Vitamin C has been studied extensively in this area and shows the dosage and duration of supplementation can affect the effectiveness of vitamin C in cold duration and prevention. 

The evidence suggests that for the common cold vitamin C is most effective when taken prophylactically (for prevention) combined with a higher dose at symptom onset (7). 

The higher dose at symptom onset can decrease the duration by 26%. Moreover some studies show that if vitamin C was taken only at the onset of symptoms there was no shortening of cold symptoms (7). Due to the half life of vitamin C being 5 hours it's important to be taking vitamin C across the day as there is limited bioavailability in one large dose (6). 

Taking vitamin C for prevention (Prophylactically) has inconsistent evidence. A meta-analysis showed that people supplementing prophylactically with vitamin C were only 4% less likely to develop a cold (8). However when those people do get sick the severity and duration seems to be less than those who were not supplementing prior to the cold. Those people under extreme stress such as endurance athletes may reduce their cold risk by half (8).  Due to the dosage variation in the studies some being very low, perhaps a higher dose could be more effective in cold prevention. 

If you want to harness the power of vitamin C for cold prevention and to reduce the severity of the cold the dosages I recommend are below.

Dosage:

Prevention (prophylactic): 200mg of Vitamin C taken twice daily. Place in a water bottle and sip across the day to maintain higher levels of vitamin C. 

Symptom onset: 2g per day of vitamin C taken across a day. Take 150-200mg every 2hours to maintain plasma concentration (4-6 times a day). If loose stools occur then reduce dosage by 50mg until symptoms reside.

Oral vs Liposomal Vitamin C: What supplement should I buy?

Just walking into a health shop you can become overwhelmed with the variety of kinds of vitamin C. In terms of oral bioavailability some studies suggest that liposomal vitamin C is superior. What is a liposome? A liposome is a particle that is used to encapsulate the water soluble vitamin C particle. Liposomal forms have shown to produce on average higher concentrations in the blood of vitamin C and take a longer time to be broken down and excreted from the body in comparison to powder forms of vitamin C (9). The dosage is important here, 5g of liposomal vitamin C is required to achieve higher levels of vitamin C in the plasma than non liposomal vitamin C. 

In the context of oral administration and absorption Liposomal forms of vitamin C seem to be superior.

Now that we have discussed the immune system benefits of vitamin C, I hope you are looking at your vegetables and fruit with new found appreciation for what they do for you. I hope this supports your optimal health this winter. 

If you have further questions or a specific condition and wondering how vitamin C may help you please get in touch or book an appointment using the button below.

1. Rice, M. E. (2000). Ascorbate regulation and its neuroprotective role in the brain. Trends in neurosciences, 23(5), 209-216.

2. Pavlovic, V., & Sarac, M. (2011). A short overview of vitamin C and selected cells of the immune system. Central European journal of medicine, 6(1), 1-10.

3. Dahl, H., & Degré, M. (1976). The effect of ascorbic acid on production of human interferon and the antiviral activity in vitro. Acta Pathologica Microbiologica Scandinavica Section B Microbiology, 84(5), 280-284.

4. Frei, B., Birlouez-Aragon, I., & Lykkesfeldt, J. (2012). Authors' perspective: what is the optimum intake of vitamin C in humans?. Critical reviews in food science and nutrition, 52(9), 815-829.

5. Ministry of Health. (2012). NRV summary 2017. Retrieved from https://www.nrv.gov.au/resources/nrv-summary-tables.

6. Padayatty, S. J., Sun, H., Wang, Y., Riordan, H. D., Hewitt, S. M., Katz, A., ... & Levine, M. (2004). Vitamin C pharmacokinetics: implications for oral and intravenous use. Annals of internal medicine, 140(7), 533-537.

7. Ran, L., Zhao, W., Wang, J., Wang, H., Zhao, Y., Tseng, Y., & Bu, H. (2018). Extra dose of vitamin C based on a daily supplementation shortens the common cold: A meta-analysis of 9 randomized controlled trials. BioMed research international, 2018.

8. Douglas, R. M., Chalker, E. B., & Treacy, B. (2004). Vitamin C for preventing and treating the common cold (Cochrane Review). The Cochrane Library, (4), 1549-1676.

9. Łukawski, M., Dałek, P., Borowik, T., Foryś, A., Langner, M., Witkiewicz, W., & Przybyło, M. (2019). New oral liposomal vitamin C formulation: properties and bioavailability. Journal of liposome research, 1-8.