It has been known for many years that vitamin-C levels in the blood and white blood cells rapidly fall during infection and stressful conditions. Taking supplements with vitamin C could improve many aspects of an impaired immune system — including making your natural killer cells more powerful and functional.
In a quality five-year study, 144 and 161 individuals were assigned to get 50 or 500 milligrams of vitamin C. The number of common colds per 1,000 months was 21.3 for the 50 mg group and 17.1 for the 500 mg group. Yet, vitamin C did not reduce the severity or duration of colds. Older patients with pneumonia or chronic bronchitis
showed a better overall respiratory score when treated with 200 mg a day of vitamin C over four weeks.
A meta-analysis using all available literature data from 1990 to 2006 rounded up 30 clinical studies with over 11,000 patients with the common cold using more than 200 mg of vitamin C a day. Here is what it found:
Among adults and children with 9,676 total common cold episodes, there was an eight-percent drop in cold duration in adults and a 15% drop in children. Among a total of 7,045 common cold episodes, there was a modest decrease in cold severity (missed school or work, plus symptoms) in the vitamin-C group as compared to placebo group.
Among the 11,077 individuals as a whole, there was no difference in terms of incidence of common cold in the vitamin-C group compared to placebo. However, in six studies involving 642 soldiers, skiers and marathon runners exercising in very cold climates, those on vitamin C did experience a 50% reduced risk of developing a cold.
In seven studies with 3,294 common cold episodes, vitamin C did not show any significant benefit for shortening the duration of symptoms. In four studies with 2,753 episodes, vitamin C failed to show benefits over placebo in reducing the severity of symptoms. Some believe that these results weren’t more positive because the studies were using too low a dose and people were not taking hourly doses of vitamin C.
Researchers have observed that people with different illnesses require different amounts of megadose vitamin C. In general, the sicker the patient, the greater the dose required. It has been found that 80% of adults can tolerate 10 to 15 grams of vitamin C dissolved in half a cup of water and divided into four separate doses in one day without experiencing side effects such as diarrhea.
For a mild common cold, the recommend dosage is 30 to 60 grams divided into six to 10 doses a day. For a severe cold, it is 60 to 100 grams divided into eight to 15 doses a day.
For the flu, the recommended dose is 100 to 150 grams divided into eight to 20 doses a day.
There is just one controlled study that used a megadose of vitamin C frequently. Here, 463 students (aged 18-32) served as the control group and 252 students (aged 18-30) received vitamin-C treatment. It was one gram every hour for the first six hours and then one gram three times daily until cold symptoms subsided. The results: vitamin C
treatment led to an 85% decrease in common cold or influenza-like symptoms as compared to the control group.