There are fewer solid answers about probiotics than almost any other type of supplement I’ve written or read about. The evidence points to probiotics being good for you, but once you start getting deeper into the details, things get a little fuzzy.

Probiotics clearly provide health benefits, but when it comes to figuring out which ones, when, and how much, the answers aren't as clear as when you talk about creatine monohydrate, zinc, or protein.

In this article, I’ll provide the best answers I can to the following questions.

What are probiotics?

According to the World Health Organization, a probiotic is a "live microorganism which when administered in adequate amounts benefits the host."

The key is that the organisms must benefit the host, and that you consume enough to make a difference.

You already have an entire world of critters living on your skin and throughout your digestive system. Most of them are partying in your intestines, where the good ones binge on fiber and the bad ones binge on sugar.

Okay, it might not be that simple, but I'm trying to make this mildly entertaining for a blog post about bacteria.

I'll focus on the health benefits of probiotics in humans. However, probiotics might be beneficial to your dog, cat, or pet orangutan.

The foods you eat, water and other beverages you drink, and environment you live in all influence the types of bacteria living in and on us.

A quick change to your diet or environment can really mess with the balance of your gut flora. You've probably experienced that if you've ever drank the tap water at a hotel in Mexico or even gone on a restrictive diet, like a ketogenic or vegan diet.

You've housed good and bad bacteria from the moment of your birth.

.ugb-c85d1fd-wrapper.ugb-container__wrapper{border-radius:12px !important;background-color:#f1f1f1 !important}.ugb-c85d1fd-wrapper.ugb-container__wrapper:before{background-color:#f1f1f1 !important}.ugb-c85d1fd-content-wrapper > h1,.ugb-c85d1fd-content-wrapper > h2,.ugb-c85d1fd-content-wrapper > h3,.ugb-c85d1fd-content-wrapper > h4,.ugb-c85d1fd-content-wrapper > h5,.ugb-c85d1fd-content-wrapper > h6{color:#222222}.ugb-c85d1fd-content-wrapper > p,.ugb-c85d1fd-content-wrapper > ol li,.ugb-c85d1fd-content-wrapper > ul li{color:#222222}@media screen and (min-width:768px){.ugb-c85d1fd-content-wrapper.ugb-container__content-wrapper{width:100% !important}}

Factors That Affect a Newborn's Microbiome

A healthy gut starts at birth and contains Escherichia, Clostridium, Bacteriodes, and Bifidobacterium. The following are factors that affect the health of a newborn's gut.

GeneticsMethod of childbirthAntibiotics useBreast vs. bottle feedingStress or inflammatory level of mother

Though probiotics can be added to infant formula, there's little to no evidence to suggest formula feeding can be as effective as breast feeding.

What do probiotics do?

Probiotics affect your health in four different ways. They:

Compete with pathogens for adhesion sites and nutrients. When probiotics outnumber pathogens, there's a greater chance the pathogens won't have a place to set up camp and multiply.Produce byproducts that improve your health, such as short-chain fatty acids, used by the endothelial cells lining your gut, creating a barrier between your gut and circulation.Enhance immune function.Influence other organs and tissues by producing neurotransmitters.

Just as a cow's manure benefits the crops in a farmer's field, byproducts of probiotics benefit the environment of the gut, and the cells that live there.

Beneficial Byproducts of ProbioticsOrganic acidsHydrogen peroxideBacteriocins (peptides that prevent the growth of certain pathogensBacteriocin-like inhibitory substancesConjugated linoleic acid (CLA)Gamma-amino butyric acid (GABA)Short-chain fatty acids (SCFAs)

What's a genus, species, or strain?

When you see probiotics on a food or supplement label,