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Issue #39 (January 2018)

From the Editor

Volume 1

Welcome to the first volume of the NERD for the new year! In this volume, we review a meta-analysis looking at selenium supplementation’s effect on cardiovascular disease, whether supplementation with bicarbonate helps running performance, and whether building tolerance to caffeine can interfere with its ergogenic effects.

That last subject raises a question I often hear: what’s better — to cycle caffeine usage, or to use it regularly? We’ve covered this question on the Examine.com nutrition blog in the past, and the answer is: it depends on your goals.

The caffeine study we cover in this volume of the NERD (spoiler alert!) found that building caffeine tolerance can lead to a reduction in caffeine’s ergogenic effects for endurance. In contrast, a study done in mid-2017 found that caffeine still had similar ergogenic effects in people who reported both low and high habitual intakes. However, there may not be a contradiction between these two studies, since the one that found no reduction in ergogenic effects used a dose double that of the study we reviewed in this volume of the NERD. Furthermore, the dose that was used in order to boost day-of performance was higher than the highest average daily intake. Finally, in the study we reviewed in this issue, caffeine did provide a little boost, but was statistically indistinguishable from placebo. Being that this is a rather small trial, a real boost may be present; it’s just smaller in people habituated to caffeine.

My take on this evidence is that ergogenic effects don’t quite disappear even in chronic caffeine users; it’s just that a little bit of a higher dose may be needed in order to get an effect as big as that seen in non-habituated people. So, if you want to use caffeine for its ergogenic effects, it’s better to take a little bit of a larger dose the day of your big event if you regularly drink coffee or tea. But, cycling caffeine may be better for performance goals.

On the other hand, regularly using caffeine tends to do better evidence-wise for reducing the risk of chronic disease. Of course, most people don’t habitually take caffeine pills for fun, so I’m talking more about getting caffeine from drinks like coffee or tea, since most of the studies looking at the benefits of chronic usage involve beverages, and not popping caffeine pills everyday, and it’s pretty likely that other compounds in the drinks besides caffeine are helping out in this case.

So, my current take on the evidence is that regular coffee and tea is best if chronic disease prevention is the main concern, and cycling is better (but not entirely necessary) for performance.

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

Volume 2

It looks like NERD is one step ahead of the news cycle! In the last volume, we had quite a bit to say about coffee. In addition to a review and covering coffee’s associations with various health outcomes in our first ever NERD Mini, I also talked about coffee in the editor’s intro. There, I laid out my take on the evidence concerning coffee’s health benefits, and suggested that chronic consumption is associated with lower risk of of some diseases.

But the news cycle demurs. As you may have heard, a recent lawsuit in California may lead to some coffee outlets in that state slapping warning labels on their coffee later this year. The labels would warn coffee drinkers that coffee contains acrylamide, a possible cancer-causing agent.

It’s true that coffee contains some acrylamide, a chemical which is formed when foodstuffs containing carbs are heated to high temperature. That means it’s also found in things like french fries. It’s also true that some agencies, like the U.S. Department of Health and Human Service’s National Toxicology Program state that it’s “reasonably anticipated to be a human carcinogen”. The reason why they say it’s “anticipated” to be a human carcinogen is that the strongest data suggesting acrylamide’s carcinogenic effects comes from animal studies. What’s less clear is whether ingesting the acrylamide found in in coffee or some foods translates to increased cancer risk in humans.

A 2015 meta-analysis[1] addressed this question, and found little evidence that dietary acrylamide intake was associated with any form of cancer in humans, although the data couldn’t rule out a possible association with kidney, endometrial, and ovarian cancers. But, as readers of our last volume know, the umbrella review of coffee’s health effects we discussed in last volume’s NERD Mini found a decreased risk of endometrial cancer associated with coffee intake. And, although we didn’t report it, there was no association found with ovarian cancer, either. The review was silent on coffee’s association with kidney cancer, though.

Speaking personally, the data I’ve seen isn’t going to affect my behavior at this point, but it’s useful to know, since it’s quite possible that this could spur people to look into how to roast or process coffee in ways that reduces acrylamide, which probably isn’t a bad thing. Plus, there’s certainly room for more research into both the coffee question and the broader question of acrylamides in food more generally. And everyone has their own tolerance for risk.

But perhaps I’ll rethink it a bit after my next cup of coffee.

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

See other articles in Issue #39 (January 2018) of Study Deep Dives.


  1. ^ Pelucchi C, et al. Dietary acrylamide and cancer risk: an updated meta-analysis. Int J Cancer. (2015)