Vitamin C & Respiratory Infections

A 2021 study by scientists at Harvard University looked at the effects of micronutrient supplementation – i.e. vitamin and mineral supplements – on respiratory tract infections. The study reviewed and analyzed existing data from research studies performed all over the world.

Acute respiratory tract infections (ARIs)

Acute respiratory tract infections (ARIs) – include COVID-19 – are among the leading causes of death around the world. Over the years, various micronutrients have been studied in connection with ARIs because of their known effects on immune function.

The study looked at the use of vitamin D, vitamin C, zinc and multiple micronutrient supplementation.

This is what they found:

  • Vitamin C supplementation reduced the risk of ARIs
  • It also shortened the duration of symptoms
  • Vitamin C supplementation was also shown to prevent ARIs.

In the latter point, however, there was a difference noted. Prevention was strongest among male subjects, and in what are called middle-income (as opposed to high-income countries such as the US).

Vitamin C

Even before COVID-19, back in 2017, they were the third leading cause of death worldwide. ARIs are caused by viruses and various bacteria, with a large number caused by RNA viruses.

  • Fourteen previous studies reported “significant protective effects” associated with vitamin C and a reduced risk of the common cold.
  • A dose of about 500mg/day is recommended.
  • A single large orange or grapefruit contains about 70 to 100mg of vitamin C.

The researchers called the benefits “mildly effective” and wrote that more research was needed to determine just how and if they could be used in clinical treatment.

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