Tag: nutrition

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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An odd little study from researchers at UCLA, just published in PLoS ONE (full text here; press release here) looks at how alcohol extends lifespan in worms. In fact, these particular worms double their lifespan when you given them a little booze. But “little” is the operative word here: they used ethanol diluted by a factor of 20,000:

“The concentrations correspond to a tablespoon of ethanol in a bathtub full of water or the alcohol in one beer diluted into a hundred gallons of water,” Clarke said.

And more wasn’t better: a little more doesn’t provide any additional lifespan benefits; a lot more produces “harmful neurological effects” and kills them. So the optimal dose is a tiny amount.

What does this mean for humans? Very little, at this point. Still, it’s hard not to compare the results to all the human studies that have found longevity benefits for very moderate amounts of alcohol consumption (i.e. a glass a day), but not for larger amounts. It’s still not clear whether the apparent benefits relate to the ethanol itself, or to all the antioxidants and fancy compounds found in wine (and possibly beer). Could humans be affected by a mechanism similar to what’s going on in these worms?

“While the mechanism of action is still not clearly understood, our evidence indicates that these 1 millimeter–long roundworms could be utilizing ethanol directly as a precursor for biosynthesis of high-energy metabolic intermediates or indirectly as a signal to extend life span. These findings could potentially aid researchers in determining how human physiology is altered to induce cardio-protective and other beneficial effects in response to low alcohol consumption.”

Time to go pour a tablespoon of ethanol in my bathtub, I guess!

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

A few months ago, I blogged about a study that observed correlation between in-race carb intake and race time in Ironman triathletes. What was significant about that paper is that it looked at a topic that has been studied to death in the lab, and took it out into the real world. There are a lot of “problems” with the real world that make it hard to nail down causes and effects — but ultimately, the whole point of this type of research is to understand what’s happening in the real world. So these observational studies, despite their challenges, are very important.

That’s by way of intro for another small study, just published in the International Journal of Sport Nutrition and Exercise Metabolism, from researchers in New Zealand. They looked at the nutritional intake of participants in a brutal cycling race, the K4, which covers 384K and includes 4,600 metres of climbing. The average finishing time of the 18 study participants was 16 hours and 21 minutes! The key points:

• The estimated calorie burn for the race was about 6,000 calories; the average intake was just 4,500 calories, so there was a big caloric deficit.
• There was a significant inverse relationship (p=0.023) between number of calories consumed and finishing time. The more calories you managed to cram down your gullet, the faster you finished!

Is this a surprise? Given that the race was so long, it makes sense that taking in enough energy was a significant challenge. Obviously the same thing doesn’t apply during, say, a 100-metre sprint. The question is: where’s the breakpoint, beyond which energy intake becomes a significant independent predictor of performance? I think the general assumption is that it’s probably a bit below marathon distance — so it would be really interesting to see a study like this, with a very large number of participants, at a marathon.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Great in-depth profile of Desiree Davila in the current Runner’s World, leading up to the U.S Olympic Marathon Trials later this month. One passage that caught my eye, referring back to the 2008 Trials:

Davila ran her plan, clocking 5:48 mile splits. At mile 21, she was eight seconds behind eventual third-place finisher, Blake Russell. “And then I just completely fell apart,” Davila says.

It was a fueling issue. As a track runner, competing in the 1500, the 5000, and the 10,000, Davila never had to take fluids. More to the point, she couldn’t. When she tried, everything came up. “I thought, Well, I don’t want to lose breakfast, too, so I’ll just stop drinking fluids on the course.”

That doesn’t work over 26.2 miles. Or at least not for her. She struggled to cross in 2:37:50, for 13th place.

The fueling issue would be addressed—directly. During long workouts, Davila would force herself to drink. Her system, well, rejected it. “It was actually kind of disgusting,” she says. But week after week, her body eventually adapted. “Gross,” she says, “but necessary.”

Every time I write about carbohydrate intake during long endurance races (e.g. here), I get comments from people who say “Well, that may be true for the subjects in that study, but unfortunately that doesn’t work for me. My stomach can’t handle that.” Good thing Davila didn’t just accept that as an unchangeable fact of life.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Cool field study on carbohydrate loading that I missed when it came out in the International Journal of Sports Performance over the summer, but just noticed on Amby Burfoot’s Twitter feed. Researchers enrolled 257 runners preparing for the 2009 London Marathon in a five-week online study where they entered all sorts of details about their training and diet leading up to the race. The subjects had an average age of 39, and an average finishing time of 4:34.

Needless to say, there were many factors that predicted running time: gender, BMI and training being the most obvious! The most interesting was nutrition:

In addition, although individual differences in race day diet did not strongly influence the marathon performances of recreational athletes, the amount of carbohydrate ingested during the day before race-day was identified as a significant and independent predictor of running speed. Furthermore, those runners who ingested more than 7 g carbohydrate per kg body mass during the day before the event ran faster in general and also maintained their running speed to a greater extent than those participants who consumed lower quantities of carbohydrate.

This may remind you of a study I blogged about a few months ago, showing correlations between in-race carbohydrate intake and Ironman finishing time. In this case, the better predictor is day-before carb intake, not in-race carb intake — perhaps not surprising, since a marathon is much shorter than an Ironman triathlon. Here’s the most interesting data:

The most obvious question here is: Is this correlation or causation? It’s certainly plausible — in fact, it’s probable — that the most serious runners who’ve trained best are also those who realize they should eat a lot of carbs. To address this, the researchers did a matched-pair analysis. There were 30 runners who consumed more than 7 g/kg of carbs. From the rest of the subjects, the researchers extracted another 30 runners pair-matched to the carb eaters so that there was no statistical difference in age, BMI, training data, and marathon experience between those two groups of 30.

In the graph above, the open squares are the carb eaters, and the open circles are the matched group that ate fewer carbs. The finding remains the same: the runners who ate fewer carbs ran slower — and perhaps more importantly, their speed declined more sharply during the race, particularly between 35 and 40K.

Non-randomized observational studies like this need to be treated with caution, needless to say. This isn’t “proof” that eating carbohydrates the day before the race makes you faster. But it certainly fits with our current understanding of endurance physiology, and it offers a tangible target for midpack marathoners: 7 grams of carbohydrate per kilogram of bodyweight (a number that conveniently agrees with studies that have found that a single day at 10 g/kg is enough to fully max out your glycogen stores).