There is no known cure for the common cold and the symptoms can be debilitating including a sore throat, runny nose, nasal congestion and aches and pains.
Low vitamin D levels have been associated with a variety of respiratory tract infections. A recent study examined whether taking an increased monthly dose of vitamin D reduces the frequency or severity of colds in healthy adults.
"We thought for many years that if we could push up that level of vitamin D in the body that is would help prevent upper respiratory infections or make them less severe," said Dr. Carlos Camargo, of the Massachusetts General Hospital.
Camargo and his co-authors conducted a double-blind, randomized controlled trial involving 322 adults. Participants were healthy hospital workers and students living in Christchurch, New Zealand. Half of the adults received a placebo while the other 1/2 received an increased monthly dose of vitamin D.
"The vitamin D group started off with two large boluses of vitamin D, 200,000 international units and then got 100,000 units every month," said Camargo.
This was conducted within an 18-month period with more than five times the adult-recommended daily allowance of 6000 international units of vitamin D.
"If you take healthy adults with normal levels of vitamin D in their blood and you boost them up significantly with a supplement, given every month, it has no apparent effect on the frequency or severity of upper respiratory infections," said Camargo.
The study appears in this week's Jama Journal of the American Medical Association.
"They had roughly the same number of days of missed work because of the cold, the same duration of symptoms and the same severity," the doctor said.
However, past studies involving daily dosing of vitamin D show it did help reduce acute respiratory infections in children.
"It's very important, however, to keep in mind that this group had relatively normal levels to start with, and so this might not apply to people with lower levels, with actually a vitamin D deficiency," said Camargo.
More studies are needed to clarify if there is a benefit from vitamin D supplementation in other populations and with different dosing regimens.
Study participants did not report an adverse events from taking the vitamin D.