Common coldPatient friendly summary

  •  Solar UVB light may reduce the risk of the common cold by producing vitamin D.
  • Vitamin D may reduce the risk of the common cold by strengthening the body’s immune system.

Symptoms of the common cold include sniffles, postnasal drip and nasal obstruction, sneezing, and cough.

Risk factors

Risk factors for colds include:

  • Rhinovirus:  This is the most common virus, although others also cause colds.
  • Cold weather: Chilled nasal passages cannot fight viruses.
  • Contact with infected people:  Rhinovirus easily spreads from person to person.

Sunlight exposure and common cold risk

Colds are more common in winter. Ultraviolet-B (UVB) levels are lowest. Temperatures are also low. These same factors also contribute to influenza.

Vitamin D and common cold

Vitamin D levels

In one study, vitamin D levels of 38 ng/mL (95 nmol/L) were needed to significantly lower the risk of upper respiratory infections including colds.

How vitamin D works

Vitamin D may lower cold risk by:

  • Producing cathelicidin and defensins: These proteins have antibiotic properties. They reduce the risk of bacterial and viral infections.
  • Suppressing production of inflammatory compounds: Inflammation is a response of the immune system to fight infection.


The risk of the common cold and influenza was studied in postmenopausal African-American women living in New York. Women taking 2000 international units (IU) (50 mcg)/day of vitamin D3 (cholecalciferol) had a 90% reduction in either disorder. Those taking 800 IU (20 mcg)/day had a 60% reduction. Vitamin D3 is a form of vitamin D produced in the skin. It is likely that vitamin D had similar effects on both viral infections.


There are no reported studies of treating the common cold with vitamin D.

However, taking large doses of vitamin D at the beginning of infection, say 10,000 to 50,000 IU (250 to 1250 mcg)/day for 1 to 3 days, would increase vitamin D blood levels dramatically. Cathelicidin and defensin levels would also increase. Possibly these increases would reduce the severity and length of the common cold.

Find out more...

We will be adding a detailed evidence summary on this topic in the near future.  Please check back soon to find out more.

Page last edited: 17 May 2011