Common cold and flu are one of the most frequent acute illnessess with major economical impact.
A cold is a mild viral infection of the nose, throat, sinuses and upper airways.It can cause sore throat’s, blocked or runny nose, sneezing and a cough. It usually clears up after a week or two.
A flu (short for influenza) is also common, but more severe viral illness, and is caused by different viruses. All the symptoms tend to be more sudden, severe and last longer.
Common symptoms include: high temperature (fever) over 38ºC, tiredness, weakness, headache, general aches and paines and a dry and chesty cough. Flu can causes complications (like bronchitis or pneumonia) which is related to further bacterial infection.
In this article we will look at the evidence of using popular supplements to prevent and treat these respiratory infections.
There are a limited set of well-controlled trials using echinacea to prevent or treat a cold and the quality of studies are not excellent.
Meta-analysis of twenty four double-blind trials with 4631 participants were performed by Karch-Volk et al in 2014.
There were 33 comparisons of Echinacea medicines against a placebo group.
Ten trials with thirteen comparisons investigated the effectiveness of Echinacea in preventing cold’s and 15 trials with 20 comparisons investigating treatment of colds. According to these results, using Echinacea for cold treating did not provide significant health benefits.
There is weak evidence for it’s use in cold prophylaxis, however there is not enough persuasice evidence to recommend it on a daily basis.
Raus et al have suggested that Echinacea was as effective as gold standard – oseltavir in the early diagnosed and confirmed influenza virus infections. Using echinacea was linked with reduced risk of complications and adverse events .
Meta-nalysis undertaken in 2015 by Schapowal et al has shown the health benefits of using Echinacea in recurrent respiratory infections. Echinacea was linked with reduced risk of infection and complications, especially in susceptible individuals .
Taken orally, Echinacea does not usually causes side effects, however they may have interactions with variuous drugs, pharmacist supervision would be recommended .
The European Herbal Products Comittee and UK Herbal Medicines Advisory Commitee recommended against the use of echinacea containing products in children under the age of 12.
Usage of Echinacea is not recommended for pregnant women. Breastfeeding woman should use caution with echinacea products due to insufficient safety information available 
Systematic review published in 2005 has shown that doses of 200 mg or more of vitamin C have little to no benefit in preventing and treating common cold. However, duration of cold episodes were reduced significantly, 8% in sympthoms days in adults and 14% in children .
Meta-analysis from 2013, undertaken by Hemila and Chalker which consisted of 29 trials with 11,306 pariticipants failed to prove vitamin C ability to reduce the incidence of colds in general population.
The only group who noticed any improvement in cold prophylaxis were people exposed to brief periods of severe physical acitivity (like maraton skiers and runners) .
Vitamin C is quite safe to take. It is water soluble, so the excess is excreted in urine. Larger doses of ascorbic acid can cause indigestion and diarrhoea in healthy subjects.
When taken in non-acidic form of sodium and calcium ascorbate it may minimize this effect .
According to the North American Dietary Reference recommended doses for adults should by be 90 mg/day and no more that 2 grams (2000mg) per day.
Vitamin D is not only an important factor of bone homeostatis, but also plays an important role in maintaing a good immune system.
Vitamin D metabolizing enzymes and it's receptors are present in many cell types including immune cells such as antigen-presenting-cells, T cells, B cells and monocytes .
A Study performed on 430 schoolchildren in Japan showed, vitamin D3 supplementation during the winter in dose of 1200 IU/d reduced the incidence of influenza A.
The difference between placebo and test group was significant .
It is well documented that serum levels of 25-hydroxyvitamin D (25-OHD) are inversely associated with the risk of respiratory tract infections (RTIs).
However, meta-analysis results conducted by Mao and Huang do not support routine use of vitamin D in prevention of respiratory tract infections (RTI) in healthy populations .
Another systematic review from 2015 did not support the role of vitamin D supplementation in prevention of acute respiratory infections in healthy children.
However the findings suggest that children previously diagnosed with asthma may get benefits from supplementation .
On the other hand, meta-analysis performed by Bergman et al which included 11 placebo-controlled studies of 5660 patients showed protective effect of vitamin D against respiratory tract infections, and suggested once-daily doses as the most effective one .
Another review which summarized data on vitamin D status in Europe and updates results of randomized controlled trials regarding vitamin D and acute upper respiratory tract infections was performed by Zitterman et al
The findings supported the statement that vitamin D supplements significantly reduced the risk of acute respiratory infections and proved that daily administration is more effective than high-dose bolus administration and also individuals with deficient or insufficient (30-50 nmol/l) circulating 25-OH vitamin D levels benefit the most.
Since the vitamin D deficiency is prevalent in Europe, especially in eldery and non-eu immigrants, daily oral supplementation of 1000 IU vitamind D is inexpensive measure to ensure adequate vitamin D status in individuals at risk .
Systematic review of thirteen placebo-controlled comparisons have examined the therapeutic effect of zinc lozenges on common cold episodes.
The findings show that zinc lozenges in a form of zinc acetate with daily doses over 75mg, may result in 42% in the duration of cold.
Other form of zinc with similar doses may reduce the duration by 20%, and doses less than 75 mg per day have shown no effect .
Newer meta-analysis has aim to determine whether zinc acetate lozenges have different effects on the duration of common cold symptoms originating from diffetent anatomical regions.
Zinc acetate lozenges shortened the duration of nasal discharge by 34%, nasal congestion by 37%, sneezing by 22%, scratchy throat by 33%, sore throat by 18%, hoarseness by 43%, and a cough by 46%.
Zinc lozenges shortened duration of muscle ache by 54%, but there was no difference in the duration of headache and fever.
The results also have not confirmed that the effect on nasal symptoms is less that effect on the pharyngaeal region which is more exposed to relased zinc ions .
Beta-glucans are naturally occurring polysacharides, for medical purposes extracted from cell wall of certain bacteria and fungi.
The healing and immunostimulating properties of mushrooms have been known for thousand of years in the Eastern countries.
Beta-glucans increase immunity by activation complement system, enhancing macrophages and natural killer cell function .
Study performed by Mc Farlin et al has shown that beta-glucans supplementation during 28 days postmarathon period was associated with a 37% reduction in the number of cold/flu sympthom days and 32% icrease in salivary IgA at 2 hr after exercise compared to placebo .
Another study has shown that beta-glucan supplement (250mg of Wellmune supplement /day) administered for 12 weeks can reduces upper respiratory symptoms and improve s mood state in stressed subjects .
Elderberry has been used in folk medicine for centuries to treat influenza, colds and sinusitis, and has been reported to have antiviral activity against influenza and herepes simplex.
Zakay-Rones et al have investigated efficacy and safety of oral elderberry for treating influenza A and B infections.
The study involved 60 patients, who received 15ml of eldeberry or placebo syrup four times a day for 5 days, showed eldeberry extract to relieve the symptoms of infection on average 4 days earlier and use of rescue medication was significantly less than those receiving placebo .
Tiralongo et al performed as study on 312 economy class passengers travelling from Australia to an overseas destination aimed to investigate eldeberry extract on physical, especially respiratory, and mental health.
The findings suggest that eldeberry extract can significantly reduce cold duration and severity in air travelers .
According to the provided evidence, if you want to consciousely use supplements to prevent respiratory tract infections you can take: vitamin D (at least 1000 IU/day for adults, especially if your deficient, housebound and during the winter time), and only when you are exposed to high-intensity exercise (like a maraton or people training in arctic) you can use vitamin C (200-2000mg/day) and beta-glucans (250mg/day) to protect yourselves.
To treat your cold/flu symptoms you should definately use zinc acetate lozenges with daily dose at least 75 mg (large effect), vitamin C (200-2000mg/day) (small effect), eldeberry extract and beta-glucans (moderate effect).
Remember to be extra careful to take echinacea if your breastfeeding or taking other medications (consult your pharmacist first). Children under the age of 12 are not advised to use Echinachea.
- Karch-Volk M., Barret B., Kiefer D., Bauer R., Ardjomand-Woelkart K., Linde K.., Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev 2014 Feb 20;2
- Raus K., Pleschka S., Klein P., Schoop R., Fisher P., Effects of an Echinacea-Based Hot Drink Versus Oseltamivir in Influenza Treatment: A randomized, Double-Blind, Double-Dummy, Multicenter, Noninferiority Clinical Trial., Curr Ther Res Clin Exp. 2015 Apr 20;
- Schapowal A., Klein P., Johnston S.L., Echinacea reduces the risk of recurrent respiratory tract infections and complications: a meta-analysis of randomized controlled trials. Adv Ther. 2015 Marl 32 (3): 187-200
- Echinacea (Echinacea angustifolia DC, Echinacea pallida, Echinacea purpurea): Safety. Mayo Clinic. http://www.mayoclinic.org/drugs-supplements/echinacea/safety/hrb-20059246 Retrieved 2016-03-29.
- Douglas R.M., Hemila H., Vitamin C for Preventing and Treating the Common Cold. Plos Med. 2005 Jun; 2(6) e168
- Hemila H., Chalker E., Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013 Jan 1, 1
- Pauling, Linus. (1976). Vitamin C, the Common Cold, and the Flu. San Francisco, CA: W.H. Freeman and Company
- Food and Nutrition Board, Institute of Medicine.Dietary Reference Intakes (DRIs): Estimated Average Requirements. United States National Academy of Sciences. Retrieved April 15,2016.
- Aranow C. Vitamin D and Immune System. J Investig Med. 2011 Aug; 59(6): 881-886
- Urashima M., Segawa T., Okazaki M., Kurihara M., Wada Y., Ida H., Randomized trial of vitamin D supplementation to prevent sesonal influenza A in schoolchilder 1,2,3, Am J Clin Nutr May 2010, vol. 91, no 5, 1255-1260
- Mao S., Huang S., Vitamin D supplementation and risk of respiratory track infections: a meta-analysis of randomized controlled trials. Scand J Infect Dis 2013 Sep; 45(9): 696-702
- Xiao L., Xing C., Yang Z., Xu S., Wang M., Du H., Liu K., Huang Z., Vitamin D supplementation for the prevention of childhood acute respiratory infections: a systematic review of randomized controlled trials. Br J Nutr. 2015 Oct 14; 114(7): 1026-34
- Bergman P., Lindh A.U., Bjorkhem-Bergman L., Lindh J.D., Vitamin D and Respiratory Tract Infections: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. PloS One 2013 Jun 19, 8
- Zittermann A., Pilz S., Hoffmann H., Marz W., Vitamin D and airways infections: a European persperctive. Eur J Med Res. 2016 Mar 24; 21 (1): 14
- Hemila H., Zinc lozenges may shorten the duration of colds: a systematic review. Open Respir Med J. 2011; 5: 51-8
- Hemila H., Chalker E., The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis. BMC Farm Pract. 2015 Feb; 16:24
- Akramiene D., Kondrotas A., Didziapetriene J., Kevelaitis E., Effects of beta-glucans on the immune system. Medicina 2007l 43(8): 597-606
- Mc Farlin B.K., Carpenter K.C., Davidson T., Mc Farlin M.A., Baker's yeast beta-glucan supplementation increases salivary IgA and decreseas cold/flu symptomatic days after intense exercise. J Diet Suppl. 2013 Sepl 10(3): 171-83
- Talbott S.M., Talbott J.A., Baker's yeast beta-glucan supplement reduces upper respiratory symptoms and imroves mood state in stressed women. J Am Coll Nutr. 2012 Aug 31(4): 295-300
- Zakay-Rones Z., Thom E., Wollan T., Wadstein J., Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res. 20014 Mar-Apr; 32(2): 132-40
- Tiralongo E., Wee S.S., Lea R.A. Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-blind Placebo-Controlled Clinical Trial. Nutrients 2016 Mar 24; 8(4)