Probiotics and Prebiotics

Probiotics are live microorganisms — specific strains of bacteria — that colonize your gut and allow it function optimally to process our food. If the bacterial balance is off, it can mess with our digestion and our poop. In principle, probiotics can help restore this balance.

Prebiotics are the food that the bacteria eat — typically, fiber.

Both probiotics and prebiotics can be ingested through food. Any high-fiber food serves as a prebiotic: whole grains, vegetables, fruits like bananas, etc. Probiotics are found most commonly in food that is fermented: sauerkraut, kimchi, yogurt, kombucha.

Both can also be taken through supplements. All of these sources — different foods, different supplements — have slightly different bacteria that they offer.

Probiotics for babies

Generally, babies poop easily. Breast fed babies in particular poop frequently in the first month of life (then often suddenly poop very infrequently, but the stool remains soft and easy to pass.)

However: probiotics supplements, specifically Lactobacillus reuteri DSM 17938, have some limited evidence for treatment of colic (inconsolable periods of crying several hours a day, most days of the week.)

Recommended brands:

  • Biogaia Infant Drops (L.reuteri 100 millioin CFUs in 5 drops daily) 
  • Gerber Soothe Infant Drops (L.reuteri 100 millioin CFUs in 5 drops daily)

Probiotics for older kids

Probiotics with antibiotics

One of the most common uses for probiotics is given alongside antibiotics to prevent antibiotic-associated diarrhea (AAD). When a child (or adult) gets antibiotics for an infection, the drug kills bacteria. This is its job. It kills the bacteria that are making you sick, but it also kills other bacteria, like the ones in your gut that are helping out. The result is, commonly, diarrhea.

Taking probiotics at the same time has the potential to recolonize the good bacteria to prevent this.

Per Emily Oster, A Cochrane Review of randomized trials, published in 2019, included 33 studies with a total of over 6,300 participants and showed that diarrhea was reduced by more than half (8% versus 19%) when probiotics were dosed alongside antibiotics. The reductions were larger when the doses were bigger (greater than 5 billion CFUs [colony forming units] per day), and side effects appeared minimal. Simply increasing foods with active cultures, like yogurt, won’t provide a large enough dose of healthy bacteria to make a difference, you need to use a probiotic supplement.

It is important to separate the timing of the supplement so it is not taken within several hours of a dose of antibiotic. The probiotics do not in any way compromise the antibiotics. They replace good bacteria, not harmful bacteria.

Recommended brands for preventing antibiotic associated diarrhea:

  • Culturelle Kids (L. rhamnosus GG 5 billion CFUs) 1 packet or chewable daily
  • Florastor Kids (Saccharomyces yeast 250 mg) 1 capsule or packet daily
  • Align Kids (Bifidobacterium infantis 1 billion CFUs per capsule) 1 daily

Probiotics for ongoing stomach/diarrhea/constipation problems

Here, the evidence is weaker. Per Emily Oster, In relatively large-scale randomized trial evidence  (about 1,700 children over two trials), treating children who arrived at the ER with gastrointestinal issues with probiotics did not improve their recovery. This suggests it may not be a helpful treatment with acute illness.

On the other hand, some smaller scale evidence  (on about 500 children) from the developing world shows some efficacy against persistent diarrhea. How applicable that is to richer countries is less clear. A similar point is relevant in probiotics to treat irritable bowel syndrome (IBS): there is some thought that it might help, some non-randomized evidence that might be suggestive, but nothing airtight. Same story with functional constipation.

Something that looms over this entire literature is a great deal of heterogeneity (variation in the impacts). In many cases it seems like the treatment works for some people but not others, or some particular bacteria strains work for some people and not others. Conceptually, we can see why this might be. It seems possible that some — though not all! — digestive issues are related to an imbalance in the microbiome. If this is your issue, the treatment is more likely to work. If it’s not, it won’t.

We often do not know what the problem is when kids, or adults, complain of ongoing stomach pain, loose stools, constipation, and so on. For some people, probiotics might help. This is a reason to “give it a try.” Side effects from probiotics are rare. If they work, they’ll work. And that will be great. If they don’t work, then you are no worse off than you were before.

Recommended brands: 

  • VSL#3 Junior (225 billion CFU mix of bacteria) 1 packet daily (refrigerate)
  • Culturelle Kids (L. rhamnosus GG 5 billion CFUs) 1 packet or chewable daily
  • Florastor Kids (Saccharomyces yeast 250 mg) 1 capsule or packet daily
  • Align Kids (Bifidobacterium infantis 1 billion CFUs per capsule) 1 daily
  • Probiotics for other conditions:

Probiotics are often recommended for all kinds of things: allergies, eczema, mental illness, etc. The evidence on most of these is either nonexistent or, in the case of eczema and allergies in small children, it MIGHT help (worth a try), but we cannot be confident based on data. 

Recommended brands for eczema/food allergy:

  • Florajen4Kids (6 billion CFU mixture of bacteria per packet or capsule) 1 per day
  • Culturelle Kids (L. rhamnosus GG 5 billion CFUs) 1 packet or chewable daily