By Julita Baker, PHD - Science of Food Choice

Not all foods are created equal and some benefit our microbiome more. You’ve probably heard about them before, but how much do you really know about probiotics and where to find them?

We’ve learned quite a bit about our gut microbiome (the collection of microbes living in our digestive tract) in the last three posts. If you’d like to get a refresher, here are posts 1, 2, and 3 describing the nitty-gritty of why, how, and what our gut friends are all about. We answer questions like, “How do we acquire them?” “Where do they come from?” “What is important about the gut microbiome and its connection to health?”

In the latest third post, we learned about the two main divisions of bacteria that are important to focus on in health: the phyla Bacteroidetes and Firmicutes. 

We saw there is a difference in Bacteroidetes to Firmicutes ratio in leanness versus obesity (increased Bacteroidetes: Firmicutes), that the ratio is influenced by what we eat and what lifestyle and environmental factors we expose ourselves to, and we saw that transplantation of microbes from a normal mouse to a germ-free mouse, gives the germ-free mouse the “normal” mouse phenotype, irrespective of amount eaten (meaning, our gut microbiome may determine our weight and more.).

In today’s post, we will continue the Bacteroidetes to Firmicutes story by delving into the specifics of what foods benefit our microbiome. We will start this conversation by talking first about a microbiological food component that contributes to flourishing a healthy diversity of microbes: Probiotics.  

Microbe-rich foods (aka, probiotics) and the microbiome

When you think about foods that benefit your digestive system, what comes to mind? 

Oftentimes when I ask this question in lectures, the answer is typically Probiotics. 

Indeed, probiotic-rich foods (read: microbe-rich) do benefit our microbiomes (and act on the Species level, as we discussed in our last post). Here are some examples of probiotic-rich foods:

• Kefir

• Yogurt

• Kimchee

• Sauerkraut

• Some cheeses

• Cultured sour cream

• Kombucha

• Lassi

• Buttermilk (cultured)

• Miso

• Natto

• Tempeh

Other probiotic sources that have been researched are: edible spreads (1), mayonnaise (2), meats (3), confectionary (4), plant seed extracts (5), and even beer (6). 

What are probiotics?

Probiotics, defined, are live bacteria that have been shown to provide a health benefit to the host (aka, YOU) when consumed in adequate amounts. Initially coined by Nobel Prize winner Elie Metchnikof in examining lactic acid bacteria, probiotic literally means “for life.”  

In the late 1800’s, Elie noticed that Bulgarian people had better health and lifespan, and he attributed this benefit to consuming fermented milk products. 

It’s maybe unsurprising then that food like this would influence our gut microbiology. Eat bacteria, and it changes our own gut bacteria. Intuitive enough...

 Which probiotics benefit health and help prevent disease? 

As you may have noticed on your yogurt container, the names listed are typically Lactobacillus, Streptococcus, Enterococcus, and Bifidobacterium. These are the main strains used in probiotic cultures, and their usage differs based on what food is being fermented. 

Which ones are more or less beneficial though?

Bifidobacteria seems to be particularly important to health. Studies have shown that having a higher proportion of this bacteria in your diet not only helps you have healthy gut flora but also helps you keep other bad bacteria at bay (so that when you eat some raw cookie dough and potentially expose yourself to Salmonella or E.coli, you don’t end up getting sick!) (7,8). 

What this means, is that with probiotic consumption - particularly high in Bifidobacteria -  you create a barrier (7) from bad bacteria. This serves as protection against possible pathogens colonizing and making you sick.

Increases in these intestinal barrier protectors (Bifidobacteria, but also Lactobacillus) are also recently showing reductions in metabolic syndrome markers (think: high glucose and cholesterol, high blood pressure, excess body fat) and cardiovascular risk factor markers (8). This is important because having dysregulations in the above predisposes us to heart attack, stroke, cardiovascular disease, as well as other common chronic diseases.  

Mind you, over 130 million people (over 40% of the population) are affected by some chronic disease, with heart disease, cancer, and stroke accounting for almost half of the nation’s deaths (Center for disease control, 2017).

As another interesting tidbit, Bifidobacteria is also the dominant species (90%) found in healthy breastfed infants (and in particular, Bifidobacteria infantis) (conversation with Dr. David Mills, Science of Food Choice). 

What does the research say about probiotics and health/disease prevention?

In a 2012 meta-analysis (8) looking at 74 studies, 84 trials, and over 10,000 study participants, it was shown that probiotics are thought to prevent C. Diff colonization and restore equilibrium (an infection by the bacteria Clostridium difficile that could be very dangerous. Think: diarrhea 20 x / day.). 

In this same analysis, researchers saw that taking probiotics for even a week helped in gastrointestinal (GI) disease prevention. And importantly, dosage didn’t seem to matter. 

Here, researchers examining the probiotic supplement VSL #3, which contains multiple strains of probiotic bacteria (now relabeled Visbiome), found the below strains to be beneficial to health. Look for these on your next grocery trip/probiotic endeavor:

1. Four species of Lactobacillus (L. casei, L. plantarum, L. acidophilus, and L. delbrueckii subsp. bulgaricus)

2. Three species of Bifidobacterium (B. longum, B.breve, and B. infantis)

3. One species of Streptococcus salivarius subsp. 

4. Enterococcus faecium 

5. Clostridium butyricum 

6. And Lactobacillus acidophilus combined with Bifidobacterium infantis, Bifidobacterium lactis, LGG (Lactobacillus rhamnosus), Lactobacillus casei and Streptococcus boulardii. 

 So it seems there are many health benefits to consuming probiotics, and particularly the above species. 

 Are there any negatives? 

 Caveat to Probiotics

The main concern about probiotic supplements and probiotics found in food is that we don’t precisely know to what extent the bacteria are viable (i.e. How many strains are there, really, and how many are actually still alive??). 

We also don’t yet know whether taking probiotics is healthy for everyone. For example, for someone who is immunocompromised and wanting to take a large dose of bacteria- is it healthy for them too? 

Next post- What other foods benefits (and hurts) our microbiome? 

Today we learned about specific probiotics and some of their health benefits- how they create a barrier against possible pathogens, and which strains are scientifically proven to be beneficial. The next time you go grocery shopping, pick up that kimchi, or sauerkraut, or kombucha to improve your gut flora. 

In our next post, we will delve into two other categories of foods that show influences on our gut microflora.  Aside from the live strains of bacteria that we consume, there are also Prebiotics and Resistant Starches. Stay tuned for more!

References

1. Charteris, W. P., Kelly, P. M., Morelli, L. and Collins, J. K. 2002. Edible table (bio)spread containing potentially probiotic Lactobacillus and Bifidobacterium species.. International Journal of Dairy Technology, 55(1): 44–56.

2. 2. Khalil, A. H. and Mansour, E. H. 1998. Alginate encapsulated bifidobacteria survival in mayonnaise.. Journal of Food Science, 63: 702–705.

3. Arihara, K., Ota, H., Itoh, M., Kondo, Y., Sameshima, T., Yamanaka, H., Akimoto, M., Kanai, S. and Miki, T. 1998. Lactobacillus acidophilus group lactic acid bacteria applied to meat fermentation.. Journal of Food Science, 63(3): 544–547.

4. Mattila-Sandholm, T., Myllarinen, P., Crittenden, R., Mogensen, G., Fondén, R. and Saarela, M. 2002. Technological challenges for future probiotic foods.. International Dairy Journal, 12: 173–182.

5. Schaffner, D. W. and Beuchat, L. R. 1986. Fermentation of aqueous plant seed extracts by lactic acid bacteria.. Applied and Environmental Microbiology, 51: 1072–1076.

6. Hose, H. and Sozzi, T. 1991. Probiotics fact or fiction In `Probiotics—fact or fiction?'.. Journal of Chemical Technology and Biotechnology, 51(4): 540–544.

7. Liévin V, Peiffer I, Hudault S, et al. Bifidobacterium strains from resident infant human gastrointestinal microflora exert antimicrobial activity. Gut. 2000;47(5):646-652. doi:10.1136/gut.47.5.646

8. Ritchie ML, Romanuk TN. A meta-analysis of probiotic efficacy for gastrointestinal diseases. PLoS One. 2012;7(4):e34938. doi:10.1371/journal.pone.0034938