Those of us living in North America are very aware how severe this cold and flu season has been. Perhaps you’ve been unlucky enough to suffer a bout of respiratory illness yourself.
In the United States, the cold is an extremely common virus. On average, children have between six to eight colds a year, adults two to four. (1)
As for the flu, between 250,000 and 500,000 deaths a year occur worldwide, with the highest mortality in people over the age of 65. (2)
Is there any evidence that supplementing with probiotics can help?
Today I want to write about three studies that suggest they can. The results of these trials demonstrate that probiotics can either help prevent respiratory infections or lessen their severity.
The first study I want to discuss was conducted in China and published in 2009. (3) 326 healthy children between the ages of three and five were enrolled in this six-month trial. Due to attrition for various reasons, 248 children actually completed it.
Children were excluded from the study for having any of the following conditions: anatomic alterations, intolerance to lactose, milk allergies, inflammatory diseases, Crohn’s disease, colitis, celiac disease, respiratory disease, Hirschsprung disease, cystic fibrosis, constipation or diarrhea. Children were also excluded if they were consuming probiotics either in food or supplements.
Parents were instructed not to feed their children probiotics during the duration of the trial. They were also instructed to forgo traditional Chinese medicine while their children were enrolled in the study.
Children were divided into three groups. A placebo group, a group that received Lactobaccillus acidophillus (L. acidophillus) and a third group that received both L. acidophillus and Bifidobacterium lactis (B. lactis).
Placebo and probiotics were in powder form and added to the children’s milk at a group child care center and consumed daily. The placebo contained sugar and was indistinguishable in taste and texture from the active probiotic powder.
During the 6-month trial, either authorized representatives at the child-care center or parents recorded episodes and duration of illness using a standardized questionnaire. They were asked to write down the frequency and duration of fevers, coughs and stuffy nose.
They were also instructed to jot down whether there were any doctor’s visits, if any antibiotics had been prescribed as a result as well as incidences of vomiting and diarrhea.
This chart details the results. Children receiving the lactobacillus-only probiotic (middle column) were found to have significantly lower occurrences of fever, cough and stuffy nose as compared to the placebo group (first column). They also were prescribed fewer courses of antibiotics.
Now look at the lactobacillus and bifidobacteria group in the last column. These children experienced the fewest adverse events of all three groups even though there were 112 children in this group in contrast to 104 children in the placebo cohort.
So while all of these kids were subjected to the same viruses, the outcomes were markedly different depending on the probiotics taken. In those who did get sick, duration of symptoms was also lessened in both probiotic groups:
In the placebo group, symptoms lasted an average of 6.5 days in contrast to 4.5 days in the lactobacillus-only group and only 3.4 days in the lactobacillus and bifidobacteria cohort.
The authors concluded:
“Daily probiotic dietary supplementation during the winter months was a safe effective way to reduce episodes of fever, rhinorrhea [runny nose], and cough, the cumulative duration of those symptoms, the incidence of antibiotic prescriptions, and the number of missed school days attributable to illness. L acidophilus NCFM alone was effective. There was, however, a trend for a broader protective effect with the combination of L acidophilus NCFM and B lactis Bi-07.”
Now, let’s move on to a German trial, but this time following healthy adults. (4) This study was also a randomized, double-blind, placebo-controlled trial.
This study is interesting because it was conducted over the course of two cold and flu seasons. The first arm of this trial lasted three months, between January and May of 2001, and the second arm covered a five-month period, between December of 2001 and June of 2002.
Volunteers were rejected if they met any of the following criteria: any lab work out of normal range, having congenital or immune defects, experiencing allergies, suffering from chronic or acute illnesses, history of alcohol or drug abuse, being pregnant or lactating, taking probiotics in supplements or food, or having had a flu vaccine in the last 12 months.
Participants were instructed to refrain from taking immune stimulating medications, probiotics or engage in intense physical exercise during the trial.
In the first arm, 244 participants were randomized into two groups. The placebo group received just a multivitamin and mineral formulation. The intervention group received the same, but with the addition of a probiotic coating consisting of Lactobacillus gasseri, (L. gasseri), Bifidobacterium longum (B. longum) and Bifidobacterium bifidum (B. bifidum).
In the second year, another 237 people were similarly randomized into both groups.
Participants were asked to keep track of illness by the use of a questionnaire. Symptoms to record included runny nose, stuffiness, nose blowing, yellow nasal discharge, bloody mucus, sneezing, scratchy throat, sore throat, hoarseness, cough, yellowed-bronchial secretions, headache, muscle pain, pink eye, fatigue, loss of appetite and fever.
Blood was drawn to determine immune cell counts of leukocytes, lymphocytes, B-lymphocytes, T-lymphocytes, natural killer cells, granulocytes and monocytes. Virus samples were also collected from discharge into nasal wipes. In order to assure compliance with probiotic intake, fecal samples were collected.
Of the 481 people who started this study, a total of 454 completed it. And what were the results?
“Analysis of the questionnaires showed that the use of probiotic bacteria significantly shortened the mean duration of the episodes and reduced the severity of symptoms.”
Average shortening of illness duration was two days. I don’t know about you, but anything that cuts the length of a cold by a full two days is a winner in my book! However, in this study, the researchers noted no difference in the incidence of respiratory tract infections between the two groups.
Another thing that caught my attention in this trial was the enhancement of immune cell count in the group taking the probiotics:
In the left-hand column, note the higher counts in all subsets of immune cells in contrast to those in the control group. Further proof that gut bacteria has significant effects on immune function.
The last placebo-controlled study I want to talk about was conducted in Sweden between January and May of 2007. (5)
A total of 318 healthy adults between the ages of 18 and 65 were recruited. Volunteers were excluded if they met any of the following criteria: allergies, treatment for gastrointestinal disorders, pregnancy and lactation, smoking, or getting a flu vaccine in the last twelve months.
Subjects were once again asked not to ingest any probiotics in food or supplements during the study. As in the last trial, fecal samples were collected to assess compliance in those randomized to take probiotics.
Of the 318 participants, 272 completed this trial. There were no significant differences in gender distribution, age and BMI between the placebo and probiotic groups.
Probiotics and placebo were administered in sachets that the volunteers were told to take every day with a meal.
A total of 170 colds occurred in the placebo group in contrast to only 121 in the probiotic group. Only 55% of the people in the probiotic group got one or more colds whereas 67% in the placebo group did. During the study period, the number of people who got two or more colds was 33% for the placebo group, but only 21% in the probiotic group.
In those who did come down with a cold in the intervention group, they developed their first symptoms a full month after symptoms were first experienced in the placebo group.
Once again, in those who caught a cold in the probiotic cohort, their sick days were significantly reduced: 6.2 days as opposed to 8.6 days in the placebo group. The severity of symptoms was also lessened in the probiotic cohort.
The authors of this study concluded:
“In this study, oral intake of the strains Lactobacillus plantarum HEAL 9 (DSM 15312) and Lactobacillus paracasei 8700:2 (DSM 13434) contributes to the body’s defence [sic] against common cold infections. This was reflected in a significantly…lower incidence of one or more common cold episodes. In addition, there were significantly…less days sick with common cold symptoms after intake of the probiotic product during the 12 weeks of study period. Furthermore, the total symptom score and in particular the pharyngeal [throat] symptom score…was lower in the probiotic group in comparison with the control group.”
However, there were findings in this trial that were at odds with the previous study:
Unlike the German study, most immune-cell counts were lower in the probiotic group in contrast to the control group, especially T lymphocytes, B lymphocytes and T-helper cells.
What could account for the discrepancy?
I believe the difference can be explained by the lack of supplementation with bifidobacteria. The addition of bifidobacteria to lactobacillus in the Chinese children’s study clearly cut the incidence of respiratory illness more than supplementing with lactobacillus alone.
In the German study, the inclusion of B. longum and B. bifidum appears to account for the augmented immune cell proliferation in contrast to this Swedish study. So while lactobacillus strains are proven to be effective against respiratory viruses, the addition of bifidobacteria appears to enhance the immune system.
In the next post I’ll discuss how probiotics can augment the actions of a seasonal flu shot in those over 65 years of age.