Every so often, a new idea takes hold of the nutrition and supplements market. It is typically based on a scientific finding or traditional medicine and explodes from there. Probiotics, or the idea that some bacteria are beneficial for health and eating them can increase your health or cure certain illnesses, is one such idea. The science of probiotics is based on the fact that fermented or cultured foods are common to many cultures worldwide, including foods such as kimchi (Korean), yogurt (worldwide), cheese (also worldwide), and some types of sausage. At some point, scientists discovered that the microbes in yogurt could possibly be beneficial, and the field of probiotics exploded from there. Unfortunately, enthusiasm for probiotics has far outpaced scientific evidence of their usefulness, and they are now being used to treat multiple things they may or may not affect. So how do probiotics work, and should you take them?
First, how do probiotics work? Well, the human intestine is a nutrient-rich environment, with sugars, indigestible starches, fats, proteins, etc available for use. It’s also a free-for-all environment, with ruthless competition for survival among the various bacteria (1). However, in addition to stealing nutrients from your food, bacteria produce nutrients and vitamins, such as Vitamin K. The good bacteria also provide a barrier to pathogens’ colonization (2). Consequently, the idea is that if you can add in good bacteria, they’ll settle down, provide useful byproducts to keep you healthy, and help prevent pathogens from making you sick. Some people have hypothesized they can reduce inflammation/help with depression/reduce allergies, etc. Most of these effects are unproven. What we do know is that probiotics may be helpful if you have diarrhea, and may help prevent diarrhea from antibiotics or restore the gut microbial community after it’s been destroyed by antibiotics (2).
Second, should you take one? Well, that depends on the following:
- Have you been taking antibiotics? If so, a probiotic may be helpful in rebuilding your gut microbiota and preventing a C. difficile (C. diff) infection.
- Are you having severe diarrhea?
- Do you have IBS or some other chronic gut problem?
If the answer to all of these is no, it’s unlikely you need to take a probiotic. Your gut microbiota are heavily affected by your diet, so simply ingesting helpful bacteria may not substantially change the bacteria living in your gut. Because of this factor, changing your diet to be healthy might actually be more helpful than buying probiotics–after all, if conditions aren’t hospitable for the good bacteria in the first place, flooding your gut with them won’t be terribly effective. On the other hand, if you’re eating a reasonably healthy diet, aren’t ill, and aren’t on antibiotics, your gut microbiome is probably fine, so eating probiotics isn’t going to do much (but you may feel better due to the placebo effect).
So, assuming you need and want to start a probiotic, it’s important to realize that not all probiotics are equally good. Since probiotics are considered dietary supplements, they are not evaluated for efficacy by the Food and Drug Administration (2). Consequently, they are a “buyer beware” product. So, how do you know if your probiotic of choice is any good? The following are good guidelines:
- Does the company website have any data on its efficacy? Have they published any studies?
- Does the product use a mix of strains or one strain? Is it listed with genus and species on the bottle (i.e., Lactobacillus acidophilus)
- What strains are listed on the bottle? Lactobacillus spp. and Bifidobacterium spp. are the best studied.
- Does the bottle/packaging provide a number of guaranteed live bacteria per capsule on the outside?
- Is there data that this number is accurate? (i.e., has anyone done studies?)
- Is the probiotic refrigerated? This means the bacteria are active as opposed to being freeze-dried and needing to come out of dormancy after you take them.
In conclusion, probiotics can be helpful in restoring gut microbes after antibiotic treatment, and there’s certainly no harm in eating yogurt or other cultured products. However, unless you have a condition which probiotics have actually been shown to help, it’s probably a waste of money to buy the supplements. Also, caveat emptor.
Resources and additional reading:
(1) Stecher, B. et al. 2007. Plos One. Salmonella enterica Serovar Typhimurium Exploits Inflammation to Compete with the Intestinal Microbiota. Vol 5, Issue 10
(2) National Institutes of Health. 2016. Probiotics in Depth. https://nccih.nih.gov/health/probiotics/introduction.htm
Good perspective on the difficulties of changing the gut microbiome: https://www.theatlantic.com/health/archive/2018/06/will-probiotics-ever-live-up-to-the-hype/562301/