Cures for the common cold have eluded mankind for millennia … and remain out of reach.
But credible natural remedies for colds and similar viral respiratory infections emerged in recent years.
The most promising of these – based on limited clinical evidence – are zinc and Echinacea.
Recent evidence reviews concluded that Echinacea can reduce the severity and duration of colds … although confusion remains over the most effective species, parts, constituents, and doses.
Another recent evidence review found zinc lozenges effective for reducing the duration and severity of colds … when taken within 24 hours of onset and continued for five days.
The authors also concluded that zinc reduces cold incidence, school absenteeism, and (wholly inappropriate) prescription of antibiotics in children when it's taken for at least five months.
And the South Asian herb Andrographis paniculata – known as kalmegh in India's traditional Ayurvedic medicine – has gathered positive preliminary evidence in support of its reputed anti-cold effects.
Now, a study from Massachusetts adds probiotic supplements to the list of potentially effective ways to blunt the effects of the common cold.
Surprisingly – given its role in humans' first-line immune defense and known anti-viral effects – a substantial clinical study found vitamin D ineffective for preventing or curbing colds.
Friendly bugs battled colds
Last year, the authors of an evidence review came to three clear conclusions (Popova M et al. 2012):
“Clinical trials have shown that probiotics can be used as preventive and therapeutic agents in upper respiratory tract infections [such as colds] and otitis [ear infections].
“Their mechanical properties allow them to aggregate and to compete with pathogens for nutrients, space and attachment to host [peoples'] cells.
“Consequently, they can directly antagonize pathogens and thus exert beneficial effects without directly affecting the metabolism of the host.”
A new study offers more good news for lovers of yogurt, kefir, lacto-fermented vegetables, and other foods made with the aid of friendly lactic acid bacteria.
The trial involved 198 students from Massachusetts' Framingham State University, and was conducted by Tracey Smith, Ph.D., and colleagues from the University of Medicine and Dentistry of New Jersey.
The students, who were between the ages of 18 and 25 and all lived in on-campus housing, were all free of allergies or other conditions affecting the immune system, and were not taking immunosuppressive drugs.
Each student completed surveys daily to assess the effect of the study treatment. Researchers primarily looked at health-related quality of life, but also tracked missed work and school days.
The students were divided into two groups, each assigned to a different regimen for 12 weeks:
- Placebo strawberry candy with no probiotics
- Probiotic cultures in a strawberry candy (L. rhamnosus LGG® and B. animalis BB-12®; minimum 1 billion CFU of each)
Those who took the probiotic strains suffered less and recovered more quickly from colds and similar upper respiratory infections (URIs).
Compared with the placebo group, students in the probiotic group showed three key advantages:
- Missed two fewer school days.
- Scored 34 percent lower on a scale of symptom severity.
- Recovered from their URI one-third faster – four days, compared to six days for the placebo group.
However, there was no difference in the number of lost work days in the treatment group versus the placebo group.
The findings affirm the idea that probiotic cultures confer immune-related health benefits.
The results were presented September 9, 2012 at an international conference on antimicrobial agents and infectious diseases in San Francisco. (The results will appear in an upcoming issue of the British Journal of Nutrition.)
Vitamin D flunks colds-fighting test
The human body responds to disease-causing microbes—bacteria, viruses, and other pathogens—by using two distinct but partly overlapping aspects of its immune system.
The “innate” immune system is the first line of defense against bacteria, viruses and other pathogens.
It is ancient in evolutionary terms, dating back some 60 million years to our pre-human primate ancestors.
The innate immune system – which employs proteins called “anti-microbial peptides” – can recognize microbes and viruses threatening to the body … even though the specific pathogen may never have been encountered before (Gombart AF, Saito T, Koeffler HP 2009).
But the results of a new clinical trial testing vitamin D against upper respiratory infections (URIs) – primarily colds and flu – muddy the waters.
Vitamin D supplements did not reduce the rate of URIs among 322 healthy adults in New Zealand who participated in a randomized controlled trial known as VIDARIS (Murdoch DR et al. 2012).
However, as the VIDARIS study leader David Murdoch said, “… it is important to note that very few people in our study had extremely low levels of vitamin D at the beginning. So, our findings may not apply to … people [with low vitamin D levels] and to children ...'' (UO 2012)
And Dr. Murdoch noted that vitamin D supplements are of likely benefit for bone health and for the prevention of other conditions.
The trial participants were assigned to one of two groups, each of which received monthly supplements – placebo or high-dose vitamin D3 – over a period of 18 months:
- Placebo pills
- Vitamin D3 pills providing 100,000 IU (increased to 200,000 IU for months two and three).
At the beginning of the study, the average vitamin D level of the participants was 29 ng/mL.
Vitamin D supplementation boosted those levels higher than 48 ng/mL throughout the study. (Leading researchers such as Michael F. Holick, Ph.D., M.D., of Boston University Medical Center recommend keeping vitamin D levels above 30 ng/mL.)
But the vitamin D group showed no significant advantage for any measure: the number of URIs, the duration or severity of symptoms, or the number of days of missed work.
This result remained unchanged when the analysis included winter season or baseline vitamin D blood levels.
As the authors wrote, “Further research is required to clarify whether there is benefit from supplementation in other populations and with other dosing regimens.” (Murdoch DR et al. 2012)
We presume that he means that smaller daily doses (e.g. 2,000-4,000 IUs) should be tried, versus one very-high-dose pill per month.
In an accompanying editorial, Jeffrey A. Linder, M.D., M.P.H., of Brigham and Women's Hospital and Harvard Medical School, Boston, commented on the findings of the VIDARIS trial:
“The 2011 IOM report called for additional research to determine whether vitamin D therapy reduces the incidence of respiratory tract infections. The VIDARIS trial has rigorously addressed this question. Results suggest that vitamin D should join the therapies listed in the Cochrane reviews as being ineffective for preventing or treating upper respiratory tract infections in healthy adults.” (Linder JA 2012)
That conclusion seems unbalanced and premature … but, neither can we ignore the negative outcomes of this fairly large, lengthy trial. Prudence dictates maintaining healthy vitamin D levels year-round.
Vitamin D: The latest RDAs and blood levels
In 2010, the U.S. Institute of Medicine's expert committee established higher RDAs and safe intake limits for vitamin D:
The RDA for infants from birth to one year doubled, going from 200 IU to 400 IU.
The RDA for people aged one to 70 years tripled, going from 200 IU to 600 IU.
The RDA for people aged 71 or more goes from 600 IU to 800 IU.
The Tolerable Upper Intake Level—the safe intake limit—for adults doubled, from 2,000 IU to 4,000 IU per day.
When it came to setting adequate blood levels of vitamin D, the IOM report retained the prior recommended minimum, which is 20 nanograms per milliliter (ng/mL).
However, leading researcher Michael F. Holick, Ph.D., M.D., of Boston University Medical Center says the evidence supports keeping vitamin D levels above 30 ng/mL (75 nmol/L).
Fish fit the vitamin D bill; Sockeye stand out
In addition to getting vitamin D from supplements, certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild sockeye Salmon rank as the richest source, with a single 3.5 ounce serving surpassing the US RDA of 600 IU by about 15 percent:
Vitamin D per 3.5 oz serving*
Sockeye salmon 687 IU
Albacore tuna 544 IU
Silver salmon 430 IU
King salmon 236 IU
Sardines 222 IU
Sablefish 169 IU
Halibut 162 IU
Adams JS, Ren S, Liu PT, Chun RF, Lagishetty V, Gombart AF, Borregaard N, Modlin RL, Hewison M. Vitamin D-directed rheostatic regulation of monocyte antibacterial responses. J Immunol. 2009 Apr 1;182(7):4289-95.
Cáceres DD, Hancke JL, Burgos RA, Sandberg F, Wikman GK. Use of visual analogue scale measurements (VAS) to asses the effectiveness of standardized Andrographis paniculata extract SHA-10 in reducing the symptoms of common cold. A randomized double blind-placebo study. Phytomedicine. 1999 Oct;6(4):217-23.
Copenhagen University (CU). Vitamin D crucial to activating immune defenses. March 3, 2010. Accessed at http://news.ku.dk/all_news/2010/2010.3/d_vitamin/
Gabrielian ES, Shukarian AK, Goukasova GI, Chandanian GL, Panossian AG, Wikman G, Wagner H. A double blind, placebo-controlled study of Andrographis paniculata fixed combination Kan Jang in the treatment of acute upper respiratory tract infections including sinusitis. Phytomedicine. 2002 Oct;9(7):589-97.
Gombart AF, Bhan I, Borregaard N, Tamez H, Camargo CA Jr, Koeffler HP, Thadhani R. Low plasma level of cathelicidin antimicrobial peptide (hCAP18) predicts increased infectious disease mortality in patients undergoing hemodialysis. Clin Infect Dis. 2009 Feb 15;48(4):418-24.
Gombart AF, Saito T, Koeffler HP. Exaptation of an ancient Alu short interspersed element provides a highly conserved vitamin D-mediated innate immune response in humans and primates. BMC Genomics. 2009 Jul 16;10:321.
Gombart AF. The vitamin D-antimicrobial peptide pathway and its role in protection against infection. Future Microbiol. 2009 Nov;4:1151-65. Review.
Kligler B, Ulbricht C, Basch E, Kirkwood CD, Abrams TR, Miranda M, Singh Khalsa KP, Giles M, Boon H, Woods J. Andrographis paniculata for the treatment of upper respiratory infection: a systematic review by the natural standard research collaboration. Explore (NY). 2006 Jan;2(1):25-9
Linde K, Barrett B, Wölkart K, Bauer R, Melchart D. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev. 2006 Jan 25;(1):CD000530. Review.
Linder JA. Vitamin D and the cure for the common cold. JAMA. 2012 Oct 3;308(13):1375-6. doi: 10.1001/jama.2012.13130.
Marina Rode von Essen, Martin Kongsbak, Peter Schjerling, Klaus Olgaard, Niels Ødum & Carsten Geisler. Vitamin D controls T cell antigen receptor signaling and activation of human T cells. Published online: March 7, 2010 / doi:10.1038/ni.1851
Murdoch DR, Slow S, Chambers ST, Jennings LC, Stewart AW, Priest PC, Florkowski CM, Livesey JH, Camargo CA, Scragg R. Effect of vitamin D3 supplementation on upper respiratory tract infections in healthy adults: the VIDARIS randomized controlled trial. JAMA. 2012 Oct 3;308(13):1333-9. doi: 10.1001/jama.2012.12505.
Oregon State University (OSU). Key feature of immune system survived in humans, other primates for 60 million years. August 18, 2009. Accessed at http://www.eurekalert.org/pub_releases/2009-08/osu-kfo081809.php
Popova M, Molimard P, Courau S, Crociani J, Dufour C, Le Vacon F, Carton T. Beneficial effects of probiotics in upper respiratory tract infections and their mechanical actions to antagonize pathogens. J Appl Microbiol. 2012 Jul 13. doi: 10.1111/j.1365-2672.2012.05394.x. [Epub ahead of print]
Saxena RC, Singh R, Kumar P, Yadav SC, Negi MP, Saxena VS, Joshua AJ, Vijayabalaji V, Goudar KS, Venkateshwarlu K, Amit A. A randomized double blind placebo controlled clinical evaluation of extract of Andrographis paniculata (KalmCold) in patients with uncomplicated upper respiratory tract infection. Phytomedicine. 2010 Mar;17(3-4):178-85. Epub 2010 Jan 25.
Schoop R, Klein P, Suter A, Johnston SL. Echinacea in the prevention of induced rhinovirus colds: a meta-analysis. Clin Ther. 2006 Feb;28(2):174-83. Review.
Shah SA, Sander S, White CM, Rinaldi M, Coleman CI. Evaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis. Lancet Infect Dis. 2007 Jul;7(7):473-80. Review. Erratum in: Lancet Infect Dis. 2007 Sep;7(9):580.
Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2011 Feb 16;(2):CD001364. Review.
University of Otago (UO). Study clears up speculation about vitamin D reducing colds. Wednesday, 3 October 2012. Accessed at http://m.otago.ac.nz/news/otago037974.html