Although vitamin C has been used for the prevention of common colds and other respiratory infections for many years, there is little scientific evidence to support its effectiveness. However vitamin D has been shown in numerous clinical trials to reduce risk of cold and flu.
From the vitamin D council website:
Symptoms of the common cold include sniffles, postnasal drip and nasal obstruction, sneezing, and cough.
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.
Prevention
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.
Treatment
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.
I prefer power, I think it is broken down better.
Thanks for mentioning the buffered C, I do have some stomach upset sometimes with high acid content.
The powder will be absorbed more easily, since you don't have to break down the fillers and binders that hold the tablet together. To reduce stomach upset, always take buffered C (ascorbate), try to get it with the bioflavanoids, and take with meals.
I guess the hardest factor is determining the dosage when you take powder and of course the taste. Thanks so much for your response.
I have heard that it's a matter of convenience to use tablets versus powder Vitamin C unless very large dosing is involved, then the powder is a more desired version of Vitamin C versus taking many pills.