Remember the last time your doctor prescribed an antibiotic? Chances are a prescription for yogurt came right along with the meds to cope with your gastric microbiome, the community of very small organisms (micro=small/biome=life) living in your gut. The first time anyone saw these critters was around 1590 when one Dutch scientist invented the microscope. It took another 100 years or so to create microbiology, the science of studying very small things which led to the discovery of bugs that cause disease. Happily, only a small percentage of microorganisms do this. The rest, like the ones resident in your gut, not only make life possible. They make it pleasant.
In the last 15 years, there’s been much news about what happens when they get their (figurative) hands on the food you send down. The operative words are pro-, pre- and post- biotics.
Prebiotics are foods such as fruits, veggies, cereals, and other edible plants that contain dietary fiber and complex carbohydrates which your human body can’t digest. Their job is to provide metabolic fuel for specific probiotics, the gut microbes that ferment and convert prebiotics to postbiotics which, in 2021 the International Scientific Association of Probiotics and Prebiotics formally defined as a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.”
Probiotics live naturally in fermented dairy products like yogurt and kefir. They can also be added to foods ranging from chocolate to juices, spreads, and nutrition supplements. Surprisingly, while lots of fermented foods are tasty, not all are valuable here. For example, aged cheeses, the fermented cabbages kimchi (Korean) and sauerkraut (German), and ordinary pickles may enhance your dinner but they’ll do nothing for your gut.
A Mixed Bag
Which brings us to postbiotics. The folks at Harvard Medical School define these as “the waste left behind after your body digests both prebiotics and probiotics.” They’re a mixed bag. Lots arrive via food or pills, but the residents of your very own gut microbiome are engineered to make others such as Vitamin B12, Vitamin K, folate, and a clutch of amino acids and fatty acids.
Whichever way they come, probiotics are now thought to be possibly beneficial for specific problems, but the evidence is mixed. For example, some studies suggest probiotics may relieve the symptoms of atopic dermatitis, the most common form of eczema, but the relief is at best temporary, age-related and differs with the specific probiotic.
One review of 63 randomly controlled trials found that a combination of probiotics could shorten the duration of acute infectious diarrhea in infants by about 25 hours. In 2020, when the American Gastroenterological Association reviewed 29 trials with children and adults with Crohn’s disease or ulcerative colitis, there was no proof that probiotics alone made any difference although they might modestly improve the relief provided by actual meds.
There’s ongoing interest whether probiotics can lower the amount of cholesterol floating your blood either by reducing your liver’s ability to synthesize the waxy substance or gobbling it before you can absorb it. And then there’s the really big question: Can probiotics keep you slim and trim? Um, maybe.
Research in lab mice says the microbiome may alter how the rodents absorb, store and use the energy they get from food. A seriously rigorous 2017 review of more than 1,000 overweight or obese humans in 14 clinical trials showed that Lactobacillus, the probiotic in yogurt, administered at various doses for up to 6 months produced mixed results, lowering weight and body fat in 9 trials, increasing both in 2, and doing nothing at all in 3.
In short, this is one of those works-in-progress you can expect to hear lots more about in the days to come.
Right now the simplest solution is to eat your yogurt and munch on veggies.
As the saying goes, everything old is new again.