Vitamin C for Flu Symptoms: Can It Help when Fighting the Flu?

Vitamin C for Flu Symptoms: Can It Help when Fighting the Flu?
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Vitamin C

Vitamin C is a water-soluble vitamin and powerful antioxidant. According to research[1], vitamin C was shown to raise the concentration of IgA, IgM and IgC in the blood, three of the most important immunoglobulins of the immune system. These immunoglobulins (antibodies) are responsible for attacking foreign invaders in the body such as viruses that cause the flu. IgA antibodies are found mostly at the openings of the body, like the mouth, and are ready to attack invaders entering the body. IgM antibodies are the first to respond to the intrusion of invaders and also activate other parts of the immune system to join in the attack. IgG antibodies, which make up about 70 percent of the antibodies in the blood, are extremely effective in protecting the body from viral infections.

In addition to playing a big role in boosting the immune system, vitamin C protects cells that line the respiratory tract, is needed for regeneration of vitamin E (another powerful antioxidant and immune booster), is needed for collagen formation to strengthen the respiratory system and lowers histamine levels in the blood. Histamines are substances associated with flu symptoms such as nasal congestion, sneezing and watery eyes. So what does research have to say about vitamin C for flu symptoms?


According to one study[2] involving 715 students (ages 18 to 32), megadoses of vitamin C showed positive results on cold and flu symptoms. Participants reporting symptoms in the control group were treated with decongestants and pain relievers. Participants reporting symptoms in the test group were treated with 1,000 mg of vitamin C every hour for the first six hours and then 1,000 mg three times a day thereafter. Participants not reporting symptoms in the test group were given 1,000 mg of vitamin C three times a day. Reported cold and flu symptoms in the test group decreased 85 percent compared with the control group. The study concluded that megadoses of vitamin C given before or after the appearance of symptoms prevented and relieved the symptoms in the test group as compared to the control group.

Is It Safe to Take Megadoses when Fighting the Flu?

Because vitamin C is water-soluble, the body will excrete what it does not need through urine and the bowel. However, megadoses can lead to stomach upset and diarrhea.

Consult your doctor before taking high doses of vitamin C if you are pregnant or breastfeeding, are giving to a child, are taking medications or have a medical condition.

Taking Vitamin C for Flu Symptoms

It is best to get as much vitamin C as you can from food sources. Excellent sources include citrus fruits, strawberries, cantaloupe, watermelon, papaya, mango, blueberries, tomatoes, green peppers, leafy greens, broccoli, brussels sprouts, cabbage, cauliflower and winter squash.

Buy vitamin C supplements that are made with minimal amounts of processing.

To keep vitamin C in your body, divide your daily dose up and take throughout the day.


Vitamin C has important roles in the body and a daily diet should always provide adequate amounts. When fighting the flu, the body does require more to fight the infection. However, megadoses may be necessary to see improvement in symptoms.


[1] Vitamin C and the Immune System:

[2] Journal of Manipulative and Physiological Therapeutics: The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections -

We Research Health: Information on Vitamin C -

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