Tag: nutrition

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Just a decade ago, our concept of “healthy eating” was so simple and straightforward: fat is bad. These days, not so much. Amby Burfoot’s most recent Peak Performance blog post summarizes the key points from “The Great Fat Debate” held among four highly respected nutrition experts (Walter Willett, Alice Lichtenstein, Lewis Kuller, and Darius Mozaffarian) in the current issue of the Journal of the American Dietetic Association.

There was plenty of disagreement, but some common ground. For example, total fat is less important than the type of fat: saturated fats (e.g. dairy and meat) are less desirable than unsaturated fats (e.g. olive oil). But replacing fats with processed carbs isn’t the answer, and will probably make things worse — which brings up the fundamental problem with this kind of debate. As Harvard’s Mozaffarian puts it:

Dietary recommendations that focus on selected nutrients, such as total fat or saturated fat, are often confusing for the public, result in illogical dietary decisions, and increase the potential for manipulation of nutrient targets by the food industry… If we’re eating an otherwise healthful diet including plenty of vegetable oils, fruits, vegetables, fish, and nuts, it will be much less important what the saturated fat level is.

Or as Lichtenstein (of Tufts) puts it, more simply:

I think we have to stop talking about individual dietary components because when one goes up another goes down.

Given the continuing disagreement about fundamental questions (is cholesterol bad?), it seems pretty clear to me that we don’t have enough understanding of the complex relationship between diet and health to successfully micromanage the ratios of specific nutrients. On the other hand, we have pretty unambiguous evidence about the benefits of certain patterns of eating — like getting lots of vegetables and fruit. Until the research is a little less murky, that’s the approach I’m sticking with.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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This week’s Jockology column in the Globe and Mail takes a look at some of the benefits and risks of working out in a carbohydrate-depleted state:

For decades, sports nutritionists have been devising ever more sophisticated ways to ensure your body is perfectly fuelled before, during and after every workout. With gels, bars and belt-mounted drink bottles, you can have calories within reach no matter where you are.

But what if quaffing fewer carbs and calories – or even none – resulted in a better workout?

At a recent sports nutrition conference at the Australian Institute of Sport in Canberra, researchers and coaches were buzzing about an emerging practice they refer to as “train low, compete high.” The idea is to do some of your workouts in a carbohydrate-depleted state – the nutritional equivalent of training while wearing a weighted vest – then race with a full tank of carbohydrates.

With initial research showing the technique boosts fat-burning, as well as other metabolic responses to exercise, elite athletes aren’t the only ones taking note. It remains a controversial approach – but it’s relatively easy to give it a try… [READ ON]

For more on this topic, including the idea that low-carb training might be suitable during base training but not other times of year, check out this blog entry from last month.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Two interesting articles appeared in the New York Times earlier this week, one on salt and the other on sugar. In both cases, it’s the responses rather than the research itself that are most interesting, because they nicely illustrate the confusion and contradictions that result from our endless quest to identify a single Nutritional Villain while ignoring the broader dietary and lifestyle contexts.

First, the salt. I blogged last fall about a study that found that salt intakes in Western diets haven’t changed over the past half-century, despite claims that salt is responsible for the epidemic rise in hypertension. Now a new JAMA study measured sodium levels in the urine of 3,681 healthy people over a 24-hour period (the most reliable way to determine salt intake), and then followed them for an average of 7.9 years. They found little effect on blood pressure, no effect on the risk of hypertension, and — surprisingly — those who ate less salt were more likely to die. Here’s the data showing the risk of death and non-fatal cardiovascular disease, divided into low, medium and high salt consumers:

Interesting stuff. But even more interesting is the how eager everyone in the Times article seems to be to discredit the findings. Now, criticism of studies is certainly fair game. But instead of checking for flaws in the methodology to decide whether the findings are legit, the approach here seems to start with looking at the findings and then (since they run counter to orthodoxy) deciding that the methodology must have been flawed. The only really substantive criticism aimed at the data is the following:

But among the study’s other problems, Dr. Briss said, its subjects who seemed to consume the smallest amount of sodium also provided less urine than those consuming more, an indication that they might not have collected all of their urine in an 24-hour period.

Okay, so I can see two possible hypotheses to explain this apparent anomaly:

1. Among the apparently healthy volunteers, those who had a premonition that they would die prematurely several years later were also disproportionately more likely to withhold some of their urine from the study in order to artificially reduce the amount of salt they were apparently consuming. Perhaps some underlying confounder explains it: the same character flaw that led them to hide their urine also led to the poor health decisions that eventually killed them.
2. People who eat lots of salt get more thirsty, drink more, and thus provide more urine.

I’m not saying the study is definitive or without flaws. It’s relatively small, and its subjects were young and healthy — the authors are careful to note that it doesn’t mean that reducing salt intake isn’t useful to reduce blood pressure for patients who already have high blood pressure. But the point is that the establishment response to an interesting new study isn’t “How do we explain this new data?”, it’s “How do we dismiss it?” And that’s a problem.

The sugar article, by Gretchen Reynolds, is essentially aimed as a corrective in the ongoing debate about “toxic fructose,” stirred most recently by Gary Taubes’s Times magazine article. Reynolds sums up some of the recent research on how fructose can help endurance athletes both during and after exercise. In other words, fructose is actually quite useful in some contexts. The responses below the article are quite interesting; e.g.:

While interesting, how is this article RELEVANT to the general audience that reads the NYT? The study referenced in the article relates how sugar affected “highly trained” athletes, a group that measures less than 1% of the population…

But it is relevant. Because it suggests what we really mean is not “Sugar is toxic,” but rather “Excessive sugar in the context of a sedentary lifestyle is toxic.” The first statement is a more attractive one, because it means we have a simple, well-defined enemy to attack, so all we have to do is engineer a bunch of Lo-Sugar snack foods and we’ll all be healthy again. Unfortunately, I think that’s a false promise. You can’t ignore the overall dietary and lifestyle context.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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A friend just forwarded the new Gary Taubes NYT Magazine article on Robert Lustig’s claims that sugar is “toxic.” It’s an interesting article, worth a read, and Taubes is reasonably circumspect in acknowledging the uncertainties in the current evidence. He starts with this acknowledgment:

The viral success of [Lustig’s] lecture, though, has little to do with Lustig’s impressive credentials and far more with the persuasive case he makes that sugar is a “toxin” or a “poison,” terms he uses together 13 times through the course of the lecture, in addition to the five references to sugar as merely “evil.”[…]

His critics argue that what makes him compelling is his practice of taking suggestive evidence and insisting that it’s incontrovertible. Lustig certainly doesn’t dabble in shades of gray.

Indeed, that’s precisely what’s at issue with Lustig’s lecture: not whether sugar is a problem, but whether it’s the problem. And to make that case, Taubes stacks the deck with statements like this:

The conventional wisdom has long been that the worst that can be said about sugars of any kind is that they cause tooth decay and represent “empty calories” that we eat in excess because they taste so good.

Who the heck claims this? (In journalistic jargon, phrases like “The conventional wisdom has long been…” are known as “weasel words,” because they allow you to make statements that help your argument without finding anyone stupid enough to actually say them.) It’s a convenient distortion, because it lends some misplaced novelty to the “Men Land on the Moon!” discussion that follows, about the links between sugar and metabolic syndrome. Come on, we’ve been talking about “glycemic index,” in which glucose is assigned the nominal maximum value, since the early 1980s. This is an important topic, and perhaps one that not everyone fully appreciates, but it’s tangential to Lustig’s central claim that sugar (and fructose in particular) is a “toxin.”

The central question here is really about dose. Is sugar “unsafe at any dose,” as Ralph Nader might put it? Or is it only unsafe when consumed to excess? And if the latter, what constitutes “excess”? To his credit, Taubes makes this point, though he weakens it by putting it in the mouth of someone he identifies as a lobbyist for the corn refining industry:

[S]ugar and high-fructose corn syrup might be toxic, as Lustig argues, but so might any substance if it’s consumed in ways or in quantities that are unnatural for humans. The question is always at what dose does a substance go from being harmless to harmful? How much do we have to consume before this happens?

Much of the rest of Taubes’s article explores how much sugar we’re now eating, how much it has increased, and how diseases like diabetes and cancer have increased in parallel. It makes a strong case for eating less added sugar — pretty much exactly the same case that Taubes made in his 2007 book Good Calories, Bad Calories, as far as I can tell. Heck, I was convinced in 2007, and I’ve been very conscious of my sugar intake — along with other highly refined carbohydrates — ever since then. What I don’t see here is any reason to be more scared of sugar than I was before on the basis of Lustig’s “sugar is a toxin” argument.

Taubes describes the mechanism of fructose’s action as follows:

In animals, or at least in laboratory rats and mice, it’s clear that if the fructose hits the liver in sufficient quantity and with sufficient speed, the liver will convert much of it to fat. This apparently induces a condition known as insulin resistance…

Again, scary stuff. But how is this different from, say, glucose, or even refined carbs from white bread, which are thought to stimulate insulin resistance if they enter the body “in sufficient quantity and with sufficient speed”? If we’re concluding that fructose is “toxic,” shouldn’t we also conclude that glucose and white bread and all other refined carbs are too? Oh wait, that’s what Gary Taubes proposed in 2007. So what has Lustig added? Fructose causes the same problems as other foods, but through a different biochemical pathway.

What would get my attention is evidence that cumulative exposure to fructose — independent of the rate of intake — accumulates over time to produce problems. In other words, does eating 50 pounds of sugar spread out over 30 years ultimately produce essentially the same bad effects as eating 50 pounds of sugar in a single year? Or is it only a problem when the dose comes “in sufficient quantity and with sufficient speed”?

To be clear, I have no doubt whatsoever that Lustig is right that we eat too much sugar and it’s causing health problems. I just wonder if there’s actually anyone in the country who didn’t already think that.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Does adding a bit of protein to a carb-heavy sports drink improve performance? That’s the claim of drinks like Accelerade, which boast a 4:1 ratio of carbohydrate to protein. But the research showing any performance advantage has been controversial. There’s a new study in the American Journal of Physiology: Endocrinology and Metabolism that put this to the test once again (hat tip to Amby Burfoot for pointing it out).

The study is quite complex, but basically it involved putting 12 cyclists through a two-hour cycling test at 55% maximum power while ingesting either a carbohydrate drink (at a rate of 1 gram per kilogram of body weight per hour) or a 4:1 carb-protein drink. They did a whole bunch of tests, including repeated muscle biopsies, to evaluate whether the protein boosted rates of muscle protein synthesis during exercise. The result: it didn’t.

An interesting wrinkle: the same group (from Maastricht University in the Netherlands) did an similar study on resistance training. In that case, adding protein did boost protein synthesis rates. The researchers speculate that muscle protein synthesis is blocked during actual exercise, but can take place in the short rests between sets of a strength training routine. Thus, the protein only helps for intermittent exercise.

Two final notes. First, this wasn’t a performance study, so it certainly doesn’t prove anything either way — that debate will continue, though my sense is that dominant current opinion is that protein during exercise doesn’t help endurance. Second, we’re only talking about drinks ingested during exercise; it’s clear that protein is very important after exercise.