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Issue #33 (July 2017)

From the Editor

Volume 1

We review a lot of literature concerning probiotics in the NERD, and this volume’s no different. I’ve joked with my colleagues that we should consider changing the name to Enteric Research Digest. That way, it’d be accurate and we’d get to keep the acronym to boot, which makes for less work for the graphics and layout team.

But while there’s a lot of buzz around the gut microbiome and probiotics, I’m not sure that probiotics are actually a thing, in two important respects.

First of all, they’re not a single thing, literally. “Probiotics” is a catch-all term for living microorganisms that can confer health benefits of various kinds. But there are a lot kinds of microorganisms, and there are a lot of different health effects. The most common kinds of microorganisms seen in probiotic supplements are the lactic acid bacteria and bifidobacteria. But they’re far from the only microbes called “probiotic”, and not every single species from these two classes of microbe is probiotic, either. In fact, the strain (that string of letters and numbers following the genus and species, e.g., Lactobacillus gasseri KS-13) could matter more than the species does; some genetic studies have found that different strains within a species are more genetically similar to other species than to each other! So strain matters. What also matters are the health effects you’re looking at; just because there’s evidence that a probiotic may be effective in one area of health doesn’t mean it’s “healthy” overall. So, a question like “do probiotics work?” is incomplete. A more accurate question to ask is “does strain X affect Y?”

It’s science that addresses such questions. But the science is still pretty young, which makes me less than certain that probiotics are a thing in the figurative sense, either. It’s been no secret that consuming certain fermented foods can be beneficial; humanity’s known this for centuries, if not millennia. But the actual science behind probiotics is still pretty young. Definitely promising, but young. And the pattern we see with early research is that claims tend to be downgraded with time. First, things look interesting, but as larger, more well-designed studies come out, effect sizes often shrink, and some once-promising effects disappear altogether. Mix that trend, sometimes called “the decline effect”, with the relative uncertainty around probiotics’ mechanism of action and the vast amount of probiotic strains out there, and I would personally be more surprised if all the current claims surrounding various probiotics’ benefits panned out than if they didn’t.

Fortunately, probiotics seem relatively safe unless you’re very ill or immunocompromised (but the science is still young here, too, so stay tuned), and probiotic foods are also quite tasty. So, personally, I’ll keep eating yogurt and drinking kefir. And when it comes to studies involving probiotics, I’ll be minding my GGs and KS-13s, and taking any positive findings with a grain of lyophilized microorganisms.

Gregory Lopez, MA, PharmD
Editor-in-chief, Nutrition Examination Research Digest

Volume 2

We’re not really into One Weird Tricks That Solve All Your Problems at Examine.com, except during our April Fool’s Day e-mails. But I’m actually a fan of one. Well, two, if you count Adamantium Bone Broth™.

It’s not the latest ergogenic or fat burner. Instead, it’s a way to clarify exactly what a study’s saying. And, sometimes more importantly, what it’s not saying. Let’s take as an example the paper studying fasted exercise from this volume of the NERD to show you what I mean.

Here, the population in this study was a group of healthy, young, trained women in energy balance with a BMI less than 25. The intervention was fasted, moderate-intensity aerobic exercise. The control condition was rest. And the outcome was an increase in 24-hour fat oxidation.

Spelling out the PICO for this study explicitly can tell you quite a bit. First, the results of this study may not apply to people who are not in this population, such as women with a higher BMI or untrained women. In fact, the motivation for performing this research in the first place was that previous studies looking at this issue were done only in men. Spelling out the population in detail also occasionally helps to resolve apparent conflicts in the literature. Sometimes two studies come up with two different results simply because the populations studied differed in some important way.

Conflicts between studies can also arise due to differences in intervention. This study specifically looked at moderate intensity aerobic exercise. Different intensities of aerobic exercise or resistance training may not yield similar results.

Then there’s the curious choice of control group, which compared exercise to rest. So the results of this study alone do not address the effects of fasted versus fed exercise: instead, it compared fasted exercise to just laying around. If that’s not a choice you care about, then the results of this study alone may not be useful to you - you’d have to bring in other research. The authors of this article did this in their discussion section for this exact reason.

Finally, there’s the outcome, which specifically looks at fat oxidation over 24 hours. The main reason people may care about this is that they want to shed body fat. Increased fat oxidation could be one way to do this, but the question of body fat loss is not directly addressed here. Ignoring, misinterpreting, or oversimplifying the specific outcomes of a study is a common source of overhyping when research gets translated for public consumption.

Keeping PICO in mind while reading research can help you be more precise in interpreting what exactly a study’s saying, what it’s not, and whether it’s relevant to your interests. It can also help you formulate questions you care about more clearly when thinking about nutrition and supplementation. I find it useful. Maybe you will, too.

If you don’t, maybe it’s because our population characteristics differ.

Gregory Lopez, MA, PharmD
Editor-in-chief, Nutrition Examination Research Digest

See other articles in Issue #33 (July 2017) of Study Deep Dives.