Friendly Bugs Cut Colds; Vitamin D Defeated Students’ colds were curbed by beneficial bacteria found in cultured foods; Vitamin D failed a colds-curbing trial
by Craig Weatherby
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):
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:
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:
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 more recently evolved “adaptive” immune system reacts to and remembers specific microbes to provide a more targeted, potentially more effective defense. (See “Vitamin D Activates Two Key Immune Systems”.)
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).
And, as we’ve reported, early clinical evidence affirms the idea that higher vitamin D levels may reduce the rate of severity of colds and flu: see “Vitamin D Lack Linked to Kids' Flu and Colds Risk” and “Vitamin D Cuts Flu Rate in First Clinical Trial”.
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:
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.
See our sidebars, “Vitamin D: The latest RDAs and blood levels” and “Fish fit the vitamin D bill; Sockeye salmon stand out”.
Friendly Bugs Cut Colds; Vitamin D Defeated