Vitamin C and Respiratory Infections

What Do We Know About Vitamin C?

Vitamin C is an essential nutrient in humans. Without it we die.

Most animals internally produce their own vitamin C; humans do not so we need to obtain it from the diet or other external sources  (supplements). It is a water-soluble vitamin and cannot be stored in the body.

Severe deficiency may develop within three weeks of very low intake. This can result in a sub-clinical form of scurvy that can be manifested in increased susceptibility to infections. This is often shown initially by easy bruising.

Diets lacking in fruits and vegetables (such as a low-carbohydrate diet) often do not provide enough vitamin C.

Functions of vitamin C

  • Needed for manufacture of collagen
  • Helps the body fight infections, repair wounds
  • Act as antioxidant
  • Enhances iron absorption.

Primary food sources:

Fruits: guava, oranges, lemons, limes, strawberries, cantaloupe, grapefruit, kiwi fruit

Vegetables: broccoli, green and red peppers, collards, tomato, potatoes, ready to eat cereals (fortified)

FYI: The RDA for vitamin C is 15-75 mg/d for children, 75 mg/d for adult women, 90 mg/d for adult men, and 85 to 120 mg for pregnant and breastfeeding women.

The Tolerable Upper Limit is 2000 mg/d. Oral Intakes of 1 gram or more a day can cause nausea, cramps, and diarrhea and may increase the risk of kidney stones.

Impact on Infections

Some studies show that in common infectious diseases, supplemental vitamin C lessens the severity and duration of symptoms.

In severe respiratory diseases such as bronchitis or pneumonia, vitamin C has been shown to reduce symptoms and shorten hospital stays. Some studies report rapid clearance on chest x-rays of patients with lung infections, following intravenous vitamin C treatment.

From the Linus Pauling Institute (LPI) at Oregon State University comes this:

“March 13, 2020 – The Linus Pauling Institute is closely watching the clinical trials with intravenous (IV) vitamin C and COVID-19-related pneumonia with great interest. However, there currently are no available data to show vitamin C can prevent or successfully treat COVID-19 infections. Once the trial data are available for review, the LPI will comment on the efficacy of IV vitamin C in COVID-19.

In 1970, Dr. Linus Pauling, Nobel Prize winner,  published Vitamin C and the Common Cold, a book that revolutionized the way the world viewed vitamin C and infectious disease. Dr. Pauling believed that increasing the daily dose of vitamin C could help the body mount a strong immune response when confronted with a respiratory infection.

Many people worldwide have reported better health after taking large amounts of vitamin C. To date, clinical trials have shown that vitamin C supplements can shorten the duration of the common cold. However, there are no data to suggest that vitamin C supplements can stop respiratory infections in the general population.  Results from trials with participants undergoing heavy physical activity indicate a benefit of oral vitamin C on common cold incidence. There are no such trials on influenza or coronavirus.

The LPI continues to advocate for rigorous research on both oral and IV vitamin C for treating both inflammation and infection. Yet, the facts are that there have been few rigorous studies on vitamin C and respiratory infections. Clinical trials with IV vitamin C and coronavirus-related pneumonia are currently underway in China. These trials are of great interest to the LPI, and we will monitor them closely.

Meanwhile, the LPI recommends taking these steps to support a healthy immune system: Eat a healthy diet and ensure that you meet the recommended intakes of all micronutrients, especially vitamins A, C, D, E, as well as zinc

Oregon State University has established a COVID-19 website to provide detailed and updated information; links to OSU, local, state and federal resources; and some frequently asked questions. Please regularly check this website for important updates.”

Source: Nutrition Now, Brown, Seventh Edition

Linus Pauling Institute, Oregon State University

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