The Effectiveness of Vitamin C

Preventing and Relieving the Symptons of Virus-induced Respiratory Infections

by H. Clay Gorton and Kelly Jarvis D.C., F.A.C.O.

Based on a test group of 198 subjects and a control group of 463 subjects

The Journal of Manipulative and Physiological Therapeutics, Nov. 1999

Abstract Objective: To study the effect of mega doses of vitamin C in relieving and preventing flu and cold symptoms in a test group as compared to a control group.

Design: This is a prospective, controlled study of students in a technical training facility.

Subjects: A total of 463 students ranging in age from 18 to 32 years of age comprised the control group. A total of 252 students ranging in age from 18 to 30 years comprised the experimental or test group.

Method: The study was from a single training institution in a South American country (Chile) where the student population engaged in technical education as live-in, on campus residents for a period of ten days. It was in the interest of the facility to minimize absenteeism by investigating a hypothesis regarding the effectiveness of vitamin C in relieving flu and cold symptoms while the students participated in the intensive and rigorous ten-day schedule. Investigators tracked the number of reports of cold and flu symptoms among the 1991 test population of the facility compared to the reports of like symptoms among the 1990 control population. Those in the control population reporting symptoms were treated with pain relievers and decongestants while those in the test population reporting symptoms were treated with hourly doses of 1000 mg of vitamin C for the first 6 hours and then thrice daily thereafter. Those not reporting symptoms in the test group were also administered 1000 mg doses thrice daily.

Results: Comparing the test group vs the normalized control group the percentage of test group subjects reporting symptoms on day ten of the training was zero percent compared to 8 percent in the control group. Midway through the training the percentage of test group subjects reporting symptoms was two percent compared to seven percent for the control group. Overall, there was a decrease in reported symptoms in the test group of 85 percent over the control group.

Conclusion: Vitamin C administered before or after the appearance of cold and flu symptoms relieved and prevented the symptoms in the test population as compared to the control group.


Although the USRDA of vitamin C is 75 mg for an adult male and 70 mg for an adult female (1), the popular literature has recommended doses well in access of these figures for the treatment of respiratory infections (2, 3). However, an optimum dose has not yet been determined (4). In spite of significant positive results, very little work has been published in the technical literature on the effectiveness of vitamin C in the treatment and/or prevention of colds and influenza. One of the deterrents has undoubtedly been the assumption that as a water soluble vitamin, excess vitamin C is passed off in the urine, and therefore the application of mega doses is ineffective. However, Murata, et. al (1) have reported that 24-hour excretions of 5000 mg doses of vitamin C, administered in two types of time-release capsules, releasing 100% of the dose in 7.0 and 13.7 hours, were only 23.4% and 7.7%, respectively. Positive results in treating the symptoms of virus-induced respiratory infections by the application of moderate-to-large doses of vitamin C (300 mg and 2000 mg) have been reported by Bucca (2), Bernasconi (3), Hemila (4), Hunt, et. al. (5) and Peters, et. al (6).

This study, to evaluate the effect of mega doses of vitamin C in controlling flu and cold symptoms, comprised observations over 10-day intervals of 252 students in a rigidly controlled environment. Although the treatment plan was prospective, it was not randomized nor double blind. The test program on the use of vitamin C was carried out from January to September 1991, at a technical training facility in Santiago, Chile. The 463 student control group entered the training facility from January to December 1990. The control group received conventional treatment for reported symptoms.


Test climate: The test site, Santiago, Chile, is in a semiarid region, approximately 70 miles inland from the Pacific Ocean. The annual mean temperature in Santiago is 59°F, with extremes during January to September 1991, of 88°F and 36°F. Average relative humidity for the period was 68%.

Physical facilities: The technical training facility, comprising dormitories, classrooms and cafeteria, was located in a single structure with internal heating and air conditioning. Dormitory accommodations consisted of double bunks with a maximum loading of 40 square feet per occupant, although normal loading during the years 1990 and 1991 was less than 50% of capacity.

Sanitary conditions: Sanitary conditions were normal; the students showered once a day; food service personnel wore protective face masks, as required, and kitchen sanitary conditions were maintained and monitored by periodic inspection by health service professionals.

Diet: Nutritionally balanced meals of approximately 2200 calories per day were provided, comprised of approximately 20% protein, 30% lipids and 50% carbohydrates. There was a day-to-day variety in the menu, but the menu was the same for each group of students.

Training schedule: Each group of students inhabited the facility for the ten-day study program. The students followed a rigorous, highly controlled and uniform schedule. The daily routine, which was identical for each group, was as follows:

6:00— 6:30 Arise, shower, dress

6:30— 7:00 Individual study

7:00— 7:30 Breakfast

7:30— 8:30 Individual study

8:30— 12:00 Classroom study

12:00— 1:00 Lunch

1:00— 6:30 Classroom study

6:30— 7:00 Free time

7:00— 8:00 Dinner

8:00— 9:30 Classroom study

10:00 Lights out

During the 30 minutes free time, the students were permitted to leave the building for light exercise, as desired. Free time was also provided on day seven from 2:30 to 7:00 PM. Active sports, including soccer and basketball, were available, and the students were free to visit centers of interest in the city.

Experimental Population

The population comprising the test and control groups was highly homogenous. Age range and distribution are shown in Table 1. Each student was screened by a physical examination by his local physician before entering the training center to verify the absence of communicable disease or physical disability. Copies of the results of the medical examination were forwarded to the training center along with the student’s application. Each group of students arrived at the facility the day prior to the 10-day training period, and departed the day following the completion of training. Class sizes ranged from seven to 48 students, with an average class size during 1990 of 20.6 and during 1991 of 21.1.

Demographic makeup of students during 1990 was 70% Chilean, 29% Bolivian and 1% other, and during 1991 it was 73% Chilean, 26% Bolivian and 1% other. The other countries represented were Argentina, Paraguay and the Dominican Republic.


Control group: The question of respiratory infections was not specifically broached with the students during the 1990 classes. Students reported symptoms of illness at their own initiative when the symptoms were severe enough to request intervention. Colds and flu were generally not reported unless the student felt physically ill. Although records were not kept of the number requiring bed rest, in nearly every group one or more students required from half a day to three days bed rest to recuperate from influenza. Treatment consisted of administering pain relievers and decongestants. In a few cases symptoms were severe enough to require skilled medical intervention.

Test group: During the orientation period for the 1991 classes students were asked to report any existing cold or flu symptoms, and to report the earliest signs of the onset of sore throat or nasal congestion during their stay. Anyone reporting flu symptoms was treated with 1000 mg of vitamin C per hour for six hours, repeating the treatment for up to three days, as necessary, followed by 1000 mg three times a day for the remainder of the training period. Students receiving the one gram per hour treatment were required to report on their symptoms at the end of each six-hour period. All students not reporting initial symptoms were given 1000 mg of vitamin C three times a day.

A weekly clinic was held at the facility, where all students with illness symptoms were examined by a physician. Bacterial and viral throat infections were differentiated by the examining doctor during the clinic.


Control Group-1990: Figure 1 shows the percent of the students that reported flu symptoms on each of the 10 days in the training facility during 1990 and 1991. It is noted that in the control group (1990) the incidence of reported symptoms tended to decrease during the first five days and increase during the final five days. Apparently, those who entered with the flu tended to improve, while at the same time infecting others who developed symptoms during the later part of their stay. Of the 463 students passing through the training facility during 1990, a total of 104, or 22 percent, reported flu symptoms.

Test Group-1991: The higher initial incidence of reported symptoms in 1991 over 1990, as shown in Figure 1, is due to the fact that in 1991 the subjects upon entering the facility were requested to report any sign of sore throat or nasal congestion, whereas no requests to report symptoms were made in 1990. The precipitous decrease in reported symptoms with time in the test group as compared to the control group is readily apparent. The figure for day 6 represents only two individuals, and that for day 8 represents only one individual. Not a single student in the test group reported flu symptoms during the last two days, compared to 27 on the last two days in the control group. Further, and of major significance, during the entire period, January to September, 1991, reported symptoms were sufficiently mild that not one student lost any class time because of respiratory infection.

It is also important to note that those students diagnosed with streptococcus infections experienced no significant improvement as a result of the vitamin C treatment, but responded as expected to conventional penicillin treatment.

Of 47 subjects reporting flu symptoms upon entering the training facility, 23 experienced relief of symptoms with one six-hour treatment of 1000 mg of vitamin C per hour, 19 with two and five with three such treatments.

The assumption was made earlier that the disparity in initial reported symptoms between the control and test groups was due to the requirement of the test group to report the onset of symptoms no matter how mild they were. Thus, it would be expected that the actual fraction of the population that entered the training facility with prior symptoms was approximately the same for the two years in question. Assuming a roughly equal fraction of initial infections for the control and test groups, a more accurate comparison of the effect of vitamin C could be made by incorporating a normalization factor to account for the reporting difference.

The normalization factor was defined as the quotient of the average of the first three days’ reported incidence for the two groups. The data for the control group was multiplied by the normalization factor to give a truer comparison of the reported incidence between the two groups. The normalized data for the two groups is shown in Figure 2.

Assuming that prior infections did not endure for more than three days after beginning the training program, the relative effectiveness of vitamin C in preventing the onset of influenza could be quantized by dividing the normalized reported incidence of days 4 through 10 in the test group by that in the control group. Which shows a remarkable reduction of infection in the test group of more than 85 percent.


It is conclusively demonstrated that the administration of 3000 mg per day of vitamin C is effective in inhibiting the onset of cold and flu symptoms. It has also been shown that 1000 mg per hour of vitamin C is effective in eliminating pre-existing cold and flu symptoms. The earlier the treatment is applied following the onset of symptoms, the more effective is the treatment.

1990 (Control Group) Jan - Sept 1991 (Test Group)
Men Women Total Men Women Total
Number 296 167 463 169 83 252
Average Age 20.8 22.6 21.4 20.75 22.8 22.1
Maximum Age 27 32   27 30  
Minimum Age 18 19   18 20  

Table 1. Age Distribution of Experimental Population

Figure 1. Incidence of Reported Flu Symptons - Test Group vs Control Group

Figure 2. Incidence of Reported Flu Symptoms - Normalized Control Group vs Test Group


1. Murata, et al., Vitamins, Kyoto 64, 5, 1990, 285-43.

2. Bucca, Ann, Allergy, 65, 4, 1990, 311-14.

3. Bernasconi, P. and Massera, E., Drugs Exp. Clin. Res. 11, 10, 1985, 739-43.

4. Hemila, H., Does Vitamin C Alleviate the Symptoms of the Common Cold?—A Review of Current Evidence, Scand. J. Infect. Dis., Helsinki, 1994.

5. Hunt, C., Chakravorty, N.K., Annan, G., Habibzadeh, H., Schorah, C.J., The Clinical Effects of Vitamin C Supplementation in Elderly Hospitalized Patients With Acute Respiratory Infections, Int. J. Vitam, Nutr. Res. 64, 3, 1994, 212-19.

6. Peters, E.M., Goetzsche, J.M., Gobbelaar, B., Noakes, T.D., Vitamin C Supplementation Reduces the Incidence of Postrace Symptoms of Upper-Respiratory-Tract Infection in Ultramarathon Runners, Am. J. Clin. Nutr., 75, 2, Feb. 1993, 170-4.