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NMU 139 – Vitamin C and Immune

Nutrition / Natural Medicine Update No 139 (August 15, 2019)

with Dr. James Meschino


Topic: Vitamin C and the Immune System (An impressive update)

Source: Journal “Nutrients” (Nov 2017)


A fabulous review of vitamin C and immune function was published in the journal “Nutrients”, in November of 2017.  It may surprise you to know that vitamin C deficiency is the fourth leading nutrient deficiency in the United States, which is defined as a blood vitamin C level below 11 micromoles per liter (11umol/L).  Reasons for widespread vitamin C deficiency include reduced intake of vitamin C due to poor food choices, combined with the limited ability of our body to store vitamin C (so we need an adequate intake on a daily basis).  As well, our need for vitamin C increases with exposure to air pollution, smoking, second-hand smoke, alcohol consumption, and drug abuse. Our vitamin C need and our vitamin C turnover also increase when we are fighting infections, facing excessive physical or psychological stress and when battling diseases with oxidative and inflammatory components (type 2 diabetes, pre-diabetes. etc.). Our immune cells, in particular, have a high need for vitamin C. Some immune cells (neutrophils) concentrate values of vitamin C that are 50-100-fold higher than the amount of vitamin in our blood. Within immune cells, adequate vitamin C is required for an appropriate and optimal response to help prevent and fight infections. For example, vitamin C is required for immune cells to migrate to the site of infection, stimulate immune cells to engulf and destroy viruses, bacteria, and other microbes., stimulate the release of free radicals to kill various microbes and induce programmed cell death and clearance of immune cells that have been spent in the fight against infection, which inhibits permanent tissue damage and helps resolve the inflammatory process as they fight against the infection winds down.

To make a long story short, studies suggest that the ingestion of 250 mg per day of vitamin C in otherwise healthy people helps to enhance many important aspects of immune function. The goal is to achieve a vitamin C blood level above 50 umol/L, which most healthy people can achieve with a daily intake of 100-250 mg of vitamin C per day. This is can be very difficult to do from food alone and thus, vitamin C supplementation is an important consideration in achieving and maintaining optimal vitamin C status and immune function over our lifetime. As we get older and immune function declines, some studies suggest that the combination of 1,000 mg vitamin C per day and 200 IU of vitamin E per day improves immune function in people over 60. So higher doses are required as we age.

Studies also show that when fighting the common cold supplementation with 200 mg per day of vitamin C can help reduce severity and duration, and the incidence of the common cold if we are also exposed to physical stress. This level of vitamin C intake may also reduce the common cold frequency in those who previously had lower vitamin C blood levels (below 45 umol/L).  Very importantly, higher levels of intake (1,000 mg vitamin C per day) has been shown to prevent the decline in vitamin C depletion within white blood cells during an infection.

Here is a quote from the research paper itself regarding lung infections, pneumonia, and vitamin C, “Beneficial effects of vitamin C on recovery have been noted in pneumonia. In elderly people hospitalized because of pneumonia, who were determined to have very low vitamin C levels, the administration of vitamin C reduced the respiratory symptom score in the more severe patients. In other pneumonia patients, low-dose vitamin C (250 – 800 mg/day) reduced the hospital stay by 19% compared with no vitamin C supplementation, whereas the higher-dose group (500 – 1600 mg/day) reduced the duration (hospital stay) by 36%. Vitamin C supplementation also showed a positive effect on the normalization of chest X-ray, temperature, and erythrocyte sedimentation rate (a marker of inflammation and infection).  Since prophylactic vitamin C administration also appears to decrease the risk of developing more serious respiratory infections, such as pneumonia, it is likely that the low vitamin C levels observed during respiratory infections are both a cause and a consequence of the disease.” This means that during an infection vitamin C turnover occurs more rapidly as immune cells draw down on their vitamin C stores to fight the infection. As vitamin C becomes more and more depleted within immune cells they become less and less effective, allowing more serious infections like pneumonia to take hold and progress. As the researchers so aptly concluded, “Thus, it is apparent that vitamin C is necessary for the immune system to mount and sustain an adequate response against pathogens, whilst avoiding excessive damage to the host. “

Here is another quote from the review paper, “Following surgery, patients require relatively high intakes of vitamin C in order to normalize their plasma vitamin C status (e.g., ≥500 mg/day), and administration of antioxidant micronutrients, including vitamin C, to patients with disorders in wound healing, can shorten the time to wound closure. “

With respect to histamine release in allergy sufferers, studies show that vitamin C supplementation between 125 – 2,000 mg per day can decrease histamine levels in allergic patients, helping to suppress their symptoms. Intravenous infusion of 7,500 mg of vitamin C has also shown impressive outcomes in this regard in allergy sufferers.  Remember that it is immune cells (eosinophils, basophils and mast cells) that release histamine during an allergic response.

Vitamin C supplementation has also suppressed inflammation in type 2 diabetics and improved blood sugar regulation when ingested at a daily dosage of 500 mg, twice daily.

Type 2 diabetics are known to have lower vitamin C blood levels, which also impairs their infection-fighting and wound healing ability.

In conclusion, most healthy individuals can help to optimize immune function with an intake of 100-250 mg of vitamin C per day. When fighting or recovering from an infection, during wound healing or battling conditions such as type 2 diabetes or allergies, higher daily vitamin C supplementation doses have been shown to be beneficial. Of course, you must always check with your physician before making any changes to your diet or supplementation program, as vitamin C supplementation at the doses described in this report can be contra-indicated if you have certain health conditions.


I have included the research paper cited here in the text below.



Carr A and Maggin S. Vitamin C and immune function. Nutrients. 2017 Nov.9(11):1211


Eat Smart, Live Well, Look Great,

Dr. James Meschino

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