Fighting the Common Cold and the Flu

Fighting the Common Cold and the Flu
Part One

The cold and flu season is upon us again. And this has many concerned about getting sick. However, there are many natural steps that have been proposed to reduce one's risk of contracting a cold or flu or to lessen their severity if one does get sick. But how many of these strategies actually work?

To try to answer this question, I performed various searches on PubMed. This site indexes abstracts from thousands of health-related journals. Below is a summary of the results of my research. If the reader would like to see the actual abstracts that I looked at, references are given at the end of each part of this two-part article.

Lifestyle Practices

Various lifestyle practices have been promoted as being effective at reducing one's risk of contracting a cold or flu. The main ones are discussed below.

Diet:
It is often said that eating a healthy diet will help to prevent one from getting sick. And conversely, an unhealthy diet, especially one that is high in sugar, will make one more susceptible. And this just seems to make sense. If you are eating healthy, your immune system will be stronger, so you will be more able to fight invading viral agents than if you are not eating healthy.

However, I could not find any actual studies that looked at the relationship of diet and the occurrence of the cold or flu. This is not to say there is not such a relationship; there just doesn't seem to be anyone who has done the actual studies.

However, despite the lack of specific studies in this regard, following a healthy diet is a good idea for many reasons, and it very possibly might aid in the prevention of contracting a cold or the flu. A diet rich in fruits and vegetables and low in added sugars seems most likely to help in this regard.

Sleep:
Similar to the above, it is often said that getting adequate sleep will keep the immune system strong while a lack of sleep will make one more susceptible to getting sick. But again, I could not find any actual studies that have been done on this relationship. But still, it does make sense that if you are run-down from inadequate sleep you would be more susceptible to contracting a cold or flu.

Stress:
Several studies have been done on the relationship of stress and the common cold. And all the studies I looked at found a definite relationship. Those under undo stress are more likely to get sick than those not under excessive amounts of stress.

One study even purposely infected 17 people with a cold virus, but only a dozen actually got sick. Upon questioning, it was found that those who got sick had the greatest number of reported "major life events" in the previous year. So acute episodes of stress can increase one's risk of getting sick. But another study found that chronic stress was more associated with an increased risk of developing a cold than acute stress.

So both acute stress from major life events or chronic stress can increase one's risk of contracting the common cold. Controlling stress in one's life is, of course, easier said than done. I couldn't find any specific evidence, but the effects of stress probably can be mediated somewhat by using various stress reduction techniques.

Exercise:
Much research has been done on the effect of physical exercise on the immune system. Generally speaking, the studies have found that moderate exercise can increase immune function and reduce the risk of getting sick while strenuous exercise can dampen the immune system.

However, in regards to the latter, several studies found that carbohydrate intake immediately after strenuous exercise can mediate the immune suppressing effects of the exercise. So along with for restoring glycogen levels, this is one more reason for consuming a carbohydrate-rich drink immediately post-exercise. It was also noted in the studies that ensuring an adequate intake of protein and various vitamins and minerals would also help to mediate any immune suppressing effects of vigorous exercise. Moreover, one study found that the effectiveness of a flu vaccine among elderly participants was increased by vigorous exercise.

I also came across a couple of studies that looked at exercising while suffering with an upper respiratory infection, i.e. a "head cold." Both studies found that exercise at this time did not increase the severity or duration of the infection. However, it was noted that if the cold were more systemic, then exercise would not be such a good idea.

So whether moderate or vigorous, exercise is a good thing when it comes to colds and the flu, and for many other reasons as well. Just be sure to follow adequate nutritional practices along with the exercise, including a carbohydrate-rich post workout drink. And if you're sick and the cold is only above the neck, then exercise is okay but not if it is below the neck or if you have a fever.

Smoking:
As I was doing my research, I happened to come across a study done on women who smoke heavily. It found that they had a significantly greater incidence of colds than non-smoking women. And the study also found that non-smokers who lived with the smoking women also had a greater rate of colds than those not exposed to second-hand smoke.

So you can add increasing the risk of the common cold to the already long list of reasons why smokers should give up smoking, not just for themselves but also for those around them.

Hand Washing and Surface Decontamination:
Another common recommendation to prevent one from contracting a cold or flu virus is frequent hand washing. I couldn't find any studies that specifically looked at the benefits of this practice, but it does make sense. One study I came across mentioned that a cold virus could live for several hours on environmental surfaces. So touching the surface and then your mouth, nose, eyes, or ears would be a possible mode of contamination.

A related point is what the subject of the above study was about, using disinfectants on contaminated surfaces. The study found that Lysol Disinfectant Spray® and a common domestic bleach both reduced the amount of virus on the surfaces by over 99% while an ammonia-based product and an phenol-based product only reduced the contamination by 15% and 63% respectively. So cleaning contaminated surfaces with either Lysol or bleach would be another wise practice.

Supplements

Now we come to the more controversial area of this discussion. Through the years various supplements have been promoted as being effective at either preventing the common cold and the flu or at reducing the duration or severity of their symptoms. Some of the more important of these will be discussed.

Vitamin C:
Dating back to the early 1970s and Linus Pauling, mega-does of vitamin C have been promoted as a means of preventing or treating the common cold. And many studies have been done in this regard.

Most studies have found that taking high does of vitamin C on a regular basis does not prevent the common cold. So a daily intake of mega-doses of vitamin C for this purpose does not seem warranted. The only exceptions to this were three studies that looked at people who were engaging in prolonged strenuous physical activity. In these studies, 0.6-1.0 gram (600-1000 mg) of vitamin C a day produced a significant reduction in incidences of the common cold among test subjects as opposed to the control (placebo) groups. So for athletes engaged in high-intensity training and workers with very physically demanding jobs, then regular supplementation with vitamin C within this range might prove beneficial.

When it comes to taking vitamin C when one is already sick, the research is somewhat conflicting. Some studies have found that high does of vitamin C does not reduce the duration or severity of cold symptoms, but many other studies have found that it does. So as often happens with research studies, there is no clear consensus.

However, some of the studies I looked at were actually "meta-analysis" studies. These are basically researchers doing what I did-they look at many different studies on a subject and draw general conclusions from them. And what the researchers found was that those studies that found no effect from vitamin C did not use sufficient amounts.

Specifically, when the studies used one gram or less of vitamin C a day at the onset of a cold, then little or no effect was seen. However, when two or more grams were used, then the vitamin C supplementation was found to have a significant effect in reducing the duration and severity of cold symptoms.

As for exact amounts, one study administered one gram of vitamin C every hour for six hours on the first day of the onset of cold or flu symptoms and one gram three times a day on each day thereafter. The study found an 85% reduction in cold symptoms among the test subjects as compared to the placebo group. So this was a very significant effect. It should also be noted that this was the only study I found that used vitamin C for both colds and the flu.

So it would seem to get a positive effect from vitamin C intake for reducing cold symptoms, the amounts need to be along the order of several grams a day. It also seems that for best results, the total daily dose should to be spread out in smaller doses over the course of the day.

Zinc Lozenges:
Zinc, particularly in the form of lozenges, is another nutrient that has been promoted as being effective at reducing the duration and severity of the common cold. But in this case, the evidence is basically split down the middle.

In fact, one meta-analysis that I came across looked at eight different studies on the effectiveness of zinc lozenges. Four studies found that zinc lozenges reduced the duration and severity of cold symptoms while the other four found that it did not. So it really is hard to draw any conclusions about the effectiveness of zinc lozenges.

Part of the reason for these conflicting results might have to do with the pre-existing zinc status of the test subjects. It's possible that those who were helped were zinc deficient, at least on a sub-clinical level, while those who did not experience a positive effect were not zinc deficient.

Another point to note is that an excessive intake of zinc can actually depress the immune system. It is for this reason that the "upper tolerable limit" for zinc is set at 40 mg. And this level is for the total amount a person consumes from foods and supplements combined. So again, it's possible that those who did not experience benefit from zinc lozenges were already at the high end of this limit and the lozenges put them over the top and thus actually depressed their immune systems rather than enhancing it.

It should also be noted that in those studies that found a benefit from zinc lozenges, the effect was not that great. In one study, for instance, cold symptoms lasted 9.0 days in the control group verses 7.5 days in the test group.

Part Two of this article will conclude this discussion of various supplements for the common cold and for the flu and will give some recommendations.

References

Note: PMID refers to the PubMed ID number. This number is included so that the reader can easily find the referenced abstract. Simply do a search on the number on PubMed.

Stress:
Epidemiology. 2001 May;12(3):345-9. A cohort study of stress and the common cold. Takkouche B, Regueira C, Gestal-Otero JJ. PMID: 11338315.
Health Psychol. 1998 May;17(3):214-23. Types of stressors that increase susceptibility to the common cold in healthy adults. Cohen S, Frank E, Doyle WJ, Skoner DP, Rabin BS, Gwaltney JM Jr. PMID: 9619470.
J Psychosom Res. 2001 Jan;50(1):21-7. Psychological job demands as a risk factor for common cold in a Dutch working population. Mohren DC, Swaen GM, Borm PJ, Bast A, Galama JM. PMID: 11259797.
Behav Med. 1992 Fall;18(3):115-20. Development of common cold symptoms following experimental rhinovirus infection is related to prior stressful life events. Stone AA, Bovbjerg DH, Neale JM, Napoli A, Valdimarsdottir H, Cox D, Hayden FG, Gwaltney JM Jr. PMID: 1330102.

Exercise:
Int J Sports Med. 1990 Dec;11(6):467-73. The effects of moderate exercise training on natural killer cells and acute upper respiratory tract infections. Nieman DC, Nehlsen-Cannarella SL, Markoff PA, Balk-Lamberton AJ, Yang H, Chritton DB, Lee JW, Arabatzis K. PMID: 2286486.
Br J Sports Med. 2003 Aug;37(4):304-6. Effect of exercise on upper respiratory tract infection in sedentary subjects. Weidner T, Schurr T. PMID: 12893713.
Med Sci Sports Exerc. 1998 Nov;30(11):1578-83. The effect of exercise training on the severity and duration of a viral upper respiratory illness. Weidner TG, Cranston T, Schurr T, Kaminsky LA. PMID: 9813869.
Sports Med. 1999 Feb;27(2):73-80. Exercise and immune function. Recent developments. Nieman DC, Pedersen BK. PMID: 10091272.
J Gerontol A Biol Sci Med Sci. 2002 Sep;57(9):M557-62. Exercise and psychosocial factors modulate immunity to influenza vaccine in elderly individuals. Kohut ML, Cooper MM, Nickolaus MS, Russell DR, Cunnick JE. PMID: 12196490.
Curr Sports Med Rep. 2003 Oct;2(5):239-42. Current perspective on exercise immunology. Nieman DC. PMID: 12959703.

Hand Washing and Surface Decontamination:
Appl Environ Microbiol. 1993 May;59(5):1579-85. Chemical disinfection to interrupt transfer of rhinovirus type 14 from environmental surfaces to hands. Sattar SA, Jacobsen H, Springthorpe VS, Cusack TM, Rubino JR. PMID: 8390817.

Smoking:
Ann Epidemiol. 2001 May;11(4):225-31. Active and passive smoking and risk of colds in women.
Bensenor IM, Cook NR, Lee IM, Chown MJ, Hennekens CH, Buring JE, Manson JE. PMID: 11306340.

Vitamin C:
Br J Nutr. 1997 Jan;77(1):59-72. Vitamin C intake and susceptibility to the common cold. Hemila H. PMID: 9059230.
Med Hypotheses. 1999 Feb;52(2):171-8. Vitamin C supplementation and common cold symptoms: factors affecting the magnitude of the benefit. Hemila H. PMID: 10340298.
Cochrane Database Syst Rev. 2000;(2):CD000980. Vitamin C for preventing and treating the common cold. Douglas RM, Chalker EB, Treacy B. PMID: 10796569.
J Manipulative Physiol Ther. 1999 Oct;22(8):530-3. The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections. Gorton HC, Jarvis K. PMID: 10543583.
Int J Sports Med. 1996 Jul;17(5):379-83. Vitamin C and common cold incidence: a review of studies with subjects under heavy physical stress. Hemila H. PMID: 8858411.

Zinc Lozenges:
Clin Infect Dis. 2000 Nov;31(5):1202-8. Epub 2000 Nov 06. Effect of treatment with zinc gluconate or zinc acetate on experimental and natural colds. Turner RB, Cetnarowski WE. PMID: 11073753.
Ann Pharmacother. 1998 Jan;32(1):63-9. The role of zinc lozenges in treatment of the common cold. Garland ML, Hagmeyer KO. PMID: 9475824.
Am J Ther. 2002 Nov-Dec;9(6):472-5. Effectiveness of zinc gluconate glycine lozenges (Cold-Eeze) against the common cold in school-aged subjects: a retrospective chart review. McElroy BH, Miller SP. PMID: 12424502.

Fighting the Common Cold and the Flu - Part Two

The above article was published in the FitTips for One and All newsletter.
It was posted on this site December 15, 2003.

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