This blog is the fifth in my Nutrients for Immune Function Series on nutrition and its impact on immune function. If you missed the previous entries in this series, I would make sure you check them out!
This content is based on information hosted by the National Cancer Institute (NCI), called Cancer Prevention Through Immunomodulation: Does Diet Play a Role? You can listen to the entire presentation here (click “View this webinar” under the Meeting Materials heading).
Today we are talking about probiotics and prebiotics and their role in supporting your immune system. Let’s get started with some important terms and definitions.
What is Probiotic?
The first important term is probiotic. A probiotic refers to live healthy bacteria that we eat. This bacteria is found in fermented foods like, yogurt, kefir, kim chi and sauerkraut. If the food is a true probiotic, then the bacteria will be live in the food in sufficient number, the bacteria will be able to survive the stomach acid and it will arrive in your intestines in sufficient quantity in order to offer a health benefit.
What is Prebiotic?
The other important food term is prebiotic. This is the healthy food that the bacteria eat. Yes, you have to feed them! In fact, there are more bacteria living in your body then there are human cells in your body. But, don’t worry, these bacteria only eat what you can’t, namely fibre. Their favourite fibres are fructooligosaccharide (FOS), which is found in chicory root (called inulin), Jerusalem artichoke, garlic, onions and bananas, and galactooligosaccharide (GOS), which is made by enzymatic conversion of the lactose in cow milk.
Probiotics, Prebiotics and Immune Function
The NCI webinar presentation only briefly discussed the topic of probiotics, prebiotics and immune function. The presenter basically reviewed two studies that showed the relationship between diet, gut bacteria (probiotics) and cancer. I will discuss one of those studies now.
Our Immune Function Declines as We Age
The second study dealt with the fact that as we age, our microbiota (the live bacteria or probiotics in our intestines) changes. As explained in the study, as we age, the number of putrefactive bacteria (especially Clostridium perfringens) increase, and the number of beneficial bacteria groups, (such as Eubacterium spp. and bifidobarteria), decline. The aging process also leads to a marked decline in immune function, this is called immunosenescence. The change in bacteria in the gut is thought to be one of the reasons for immunosenescence.
This decline in immune function can manifest as reduced response to vaccines and reduced number of immune cells. What we eat can influence the type and quantity of bacteria in our intestines. The researchers conducting the study set out to test if giving a prebiotic supplement would improve the immune function of healthy older adults.
Can Prebiotic Supplements Improve Immune Function in Elderly People?
Forty-four, free-living elderly people (28 women and 16 men) with an average age of 69.3 years were enrolled in the study. The study subjects were given a supplement (a galactooligosaccharide mixture called Bi2muno®), which they consumed for 10 weeks.
As I mentioned earlier, Galactooligosaccharide (GOS) is a prebiotic. This means that while it is indigestible by humans, it is a very nutritious food source for our gut bacteria. GOS is produced by enzymatic conversion from cow’s milk.
The Bi2muno® supplement had a significant effect on all bacterial groups measured. The supplement reduced number of less beneficial bacteria and increased numbers of beneficial bacteria.
In addition to the beneficial changes in gut bacteria, the natural killer cell activity was significantly improved, as well phagocytosis, after the subjects took the prebiotic supplement. A more beneficial inflammatory response was also seen—anti-inflammatory cytokines were increased and the pro-inflammatory ones were decreased. These are all beneficial responses of the immune system to the prebiotic supplement.
What’s the bottom line of these studies?
What I take from this webinar presentation and the limited number of studies (one animal and one small human study) is that supporting the microbiata (good bacteria that live in our intestines) is a good strategy for supporting the immune system. It’s important to keep in mind that as we age, there is a corresponding decline in the probiotic bacterial population, as well as our overall immune function. So, this information is especially important for seniors.
In the human study, Bi2muno® provided good results. Bi2muno® is a commercially available prebiotic supplement. Galactooligosaccharides (found in the Bi2muno® supplement) appear only to be found as a supplement or in fortified foods (mostly from Japan).
Being a dietitian, I always like to mention dietary sources as well. Fructooligosaccharide is another form of prebiotic and it is found in several foods including:
- Chicory root (called inulin) and found fortified in some foods
- Jerusalem Artichoke
- Dandelion greens
- Wheat bran
- Whole wheat flour
The Bottom Line
My advice is to consume probiotics (yogurt, kefir, kim chi etc.) and prebiotics regularly. This means daily or several times per week. If you are interested in investigating the supplement used in this study, here is a link to the company’s website:
Interested in Further Reading?
If you are interested in learning more about probiotics and prebiotics, I suggest you take a look at these resources:
Cancer Res. 2014 Aug 1;74(15):4030-41.Microbiota modulate tumoral immune surveillance in lung through a γδT17 immune cell-dependent mechanism. Cheng M et al.
Am J Clin Nutr. 2008 Nov;88(5):1438-46. Modulation of the fecal microflora profile and immune function by a novel trans-galactooligosaccharide mixture (B-GOS) in healthy elderly volunteers. Vulevic J et al.
Food list from http://en.wikipedia.org/wiki/Prebiotic_(nutrition)