Fructose and Uric Acid

I understand the key to unlocking higher carbohydrate uptake is ingesting a combination of glucose and fructose. However, why is no one talking about how fructose consumption (via pure fructose powder or high fructose corn syrup not via fruit since it contains fibre) causes increases in uric acid and inflammation?

60g/30g glucose to fructose to achieve 90g carbohydrate an hour is ALOT of fructose!

The Epidemiology of Uric Acid and Fructose (nih.gov)

WHY Sugar is as Bad as Alcohol (Fructose, The Liver Toxin) - YouTube

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All these population studies are looking at correlations in a population that is largely overweight,

In the article they note that excessive body fat is a major risk factor for gout as it prevents the excretion of Uric Acid.

Also in the video on bad stuff happening in the liver, they just assume all the fructose goes to fat in the liver. This is only the case if your glycogen storage in the liver is full. Which is clearly not the case if you are burning more sugar than you are ingesting on the bike.

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Fructose metabolism is in the liver is definitely funky. It’s basically treated like alcohol. See also the classic lecture Sugar: The Bitter Truth. In low daily quantities, or higher quantities here and there for races, is probably fine. But I agree with you, chronic megadosing the stuff constantly is probably bad in virtually every dietary/lifestyle context (for more reasons than just potential gout or nafld).

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Couple of reasons. Number one, it’s an association only. Consensus hasn’t established fructose as causal (and in fact the association between sugary beverage consumption and uric acid holds in regions where fructose is not the sweetener of choice.)

As an aside, if you want to end US fructose consumption the solution is simple: end depression era government subsidies for the sugar industry. If you do that this year you’ll end America’s love affair with fructose next year. Bing, bang, done.

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Curious what you mean by this. I don’t doubt that we directly subsidize the sugar cane and sugar-beet growers, but one of the major legs of sugar-subsidy in the US is actually our import quota/tariffs. Sugar is much cheaper on the world market, so removing that would probably increase availability. Or, are we talking about corn and HFCS, which of course is an entirely different scale of problem (and ties into other programs like ethanol adulteration of gasoline)?

In the US soft drinks rely mainly on corn fructose syrup. Corn, Midwest, …


fructose and athletes. Fructose metabolism in very active people appears to be different to sedentary folks:

On Uric acid, it has been known for long that chronic endurance exercise lowers serum UA levels

Interestingly acute exercise elevates UA but fit people clear it much better.

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Thank you - interesting feedback from all of you!

I have a friend who took on pure fructose in a 60gm/30gm ratio of glucose to fructose. He told me that the addition of fructose to the glucose mix made it analogous to rocket fuel while if he had 60gm of glucose alone it was not nearly as potent.

In his experimentation, It was the only thing that he changed in his diet. After four bottles over three hard workouts, he had an episode of gout. This prompted me to do my own research!

Do any of you take on large amounts of pure fructose in your carbohydrate mixes? What has been your experience?

Just stumbled into this question and I’m going to be “that guy” dredging it up.

Yes. I often consume 60g/hr of fructose, alongside 60-70g/hr glucose, for a total of 120g/hr sugar.

My experience is that when I fuel like this, I can hold onto power for longer. Likewise for my wife who does the same thing. So, n=2.

For stronger anecdote… I have at least 15 clients who are consuming around 30g fructose per hour and have been for a couple years. Same results as me and my better half.

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At this point, nobody is questioning the performance benefits of sugar consumption for endurance sports. However, still a lot of questions about:

  • Long term side effects
  • Genetic differences among ppl
  • Optimal balance of intake vs efficient fat burning engine.
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Agreed. Lots of questions. I have a hunch that the loudness of the questions is being amplified pretty substantially by a few folks making money selling CGMs, personal monitoring technology, health & wellness related products, etc.

  • What long term side effects seem to be getting the most attention?

  • What genetic differences you considering? Differences in the gut? Long-term adaptation differences?

  • Do you mean balance of intake leaning too heavily towards carbs & sugar, causing a person to be less good at burning fat during exercise? Or chronically around the clock?

Mostly I’m just curious what the current public line of thinking is on the “is it safe, and net good” to do high-carb fueling. What have you heard or considered yourself specifically?

Sugar = diabetes = bad

I’d love to give a 3 slide presentation explaining how muscle contraction induces insulin-independent glucose uptake and thus your pancreas is a-okay when guzzling Beta Fuel and maple syrup on the bike. The thing I worry about most is my dental health.

mouth swirl with water and also chewing gum is my go to. Noticed pro riders also use gum, but perhaps that is for the caffeine.

Definitely don’t think theyre using caffeine or chewing gum. Much easier way to get caffeine in that isnt a choking hazard. They may use a different kind of gum (or pouch) with a substance that also has very high addictive properties and equally rot your teeth. I dont think there’s widespread use, and not a path I reccomend exploring (hence no names, but I guess if you know, you know), and I’m not sure the people using it is just because they’re now hooked rather than for the original purpose. I know a few elite UK cyclists have used it for appetite suppressant.

As for the gout when using fructose. When I was overweight I would have regular gout attacks. Lost a lot of weight, haven’t had one since. Using 30/60 an hour for about half a year now, still no gout issues.

Just my 2ct.

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  • I’ve read multiple testimonials in this forum of people with hypoglicemia and/or unexpected weight gain. So I question the universality of the 60-100g/hour type of advice. To me seems sensible to consider your workload carefully and your baseline body composition.

  • I know people that can’t do 1h of tempo without fueling. I find that limiting. I recently heard an interview with Alexey Vermeulen where he touches on this precisely.

  • During the offseason, professional cyclists manipulate diet and intensity to loose weight and become more efficient at burning fat …I would think this is a good pre-requisite for the common man also, before embarking in the heavy sugar fueling for intense work.

  • Do everybody respond the same to the heavy sugar fueling advice?..How do we know?

During exercise

On a personal note, this is what I do:

  • Fuel heavily during races. ~60-80g
  • Eat very well off the bike
  • For the rest, find the minimal effective dose that allows me to complete my workouts and recover.
  • Almost never fuel any workout under 1.5h. Unless is A LOT of high intensity, I might consider a gel in the middle (20g)

And doing this and getting good gains puts me so far from your universal advice of 60g-100g/hour all the time, that makes me question the validity/universality of such advice.

Thanks for your contributions.

@Vernix thank you so much for taking the time to write such a considered reply.

I responded in detail below:
TLDR:

  1. 100g/hr universality is very bad sometimes and can absolutely be harmful.
  2. People should have higher high-carb and lower low-carb days, but not for fat adaptation or metabolic flexibility.
  3. Pro cyclists are silly, as are many of their coaches.
  4. I’d love to hear your thoughts on a fueling app my wife and I designed.

END TLDR.

Begin long version:

Me too. I have read most of these (I think). They have absolutely been concerning for sure.

PSA: if anyone reading this is experiencing elevated hba1c or fasting glucose after recently attempting higher carb fueling, please speak up and chat with me on this forum. Your long-term health is on the line. Post publicly or DM or whatever. Don’t wait. Free of charge. End PSA.

This probably has as much to do with fuel timing error as anything and is unlikely to be related health.

These are the really concerning ones.

By and large, those examples have included poor management of the addition of high-carb fueling to a person’s regimen. Current overweight status, previous obesity, recent substantial weight loss, transient reduction in training volume, no concomitant reduction in off-bike consumption, and over-fueling short or easy rides are common hallmarks here.

When I read some of these stories I get to the third sentence and think “please tell me they’re not going to say 100g/hr every ride” and then my heart sinks when I read the fueling approach they’ve been taking.

The universality of the 60-100g/hr recommendation is overdone, especially for easier rides and shorter rides. And most especially for rides that are both easy and short-ish.

My wife and I feel so strongly about this that we’re currently writing an app that is designed to combat this very trend. It scales based on a host of factors rather than spitting out “oh you’re riding today? great! 60-90g/hr!”

Here are the schools of thought I see:

  • Trainerroad ppl be like “100g/hr or die.” (and a few cautious ppl being like “are we SURE sure, even for z2??”

  • Off trainerroad forum, ppl be like “40g/hr… that’s a lot, 60-90g/hr oh my word! I just do water. Should I be doing more?”

  • On slowtwitch forum, it’s more like “you don’t fuel, just get fitter” plus maybe 2 people actually doing everything beautifully, scaling carbs with duration and intensity nicely, all the way up to 120-140g/hr in some scenarios, and down to 15-30g/hr for easy recovery stuff.

  • UltraSignup forum: “I like clif bars and salted maple bourbon trail mix. I just crave real food”

Sorry that was all totally insensitive and hardcore stereotyping.

I’m really glad you’re asking hard questions to what appears to be becoming a 100g/hr dogma in a few circles.

I appreciate the publicity you’ve given it here. I just wish there was some more prominent public messaging that went like:

Hey, you lean, young, healthy, fit athletes: you should probably be erring towards 90-120g/hr for many long rides and races.

Hey, you busy parent of 2 who rides an average of 3.9 hours per week, with max session length of 90 minutes because you care for your mother in-home, and support a family of 4…. you ought to scale those numbers back by 30% and if that’s still an increase from what you’re currently doing for fueling, then just make sure you offset it a little, in your off-the-bike consumption. Weight gain and T2D is around the corner for you if you’re not careful. Make some small changes at first and it’ll pay big training dividends without ever getting near 100g/hr.

The problem is, it’s complicated to get it right! Hence, we’re writing an app and making a youtube channel. Someone needs to. Maybe an upcoming video of ours ought to be about the appropriateness of high-carb fueling.

I think this comes down to genetics and training approach as much as it does to fueling practices.

More disposition towards fast twitch = more fuel is optimal.

Less training volume = more carbs optimal for 1hr tempo.

Higher training intensity average = more carbs optimal.

Do you happen to have a link to that interview? Would love to add it to my road listening to-do list.

We might disagree a bit more here, but I think we agree on intent. As in, get fit before you start regularly slamming high carbs.

I’d posit that there should be an even higher variability in most folks carb consumption than there currently is, but not so much for reasons of seeking fat adaptation, and more just to target fueling what’s needed and optimal.

I see a lot of folks settle in at 50-80g/hr. Sometimes they drop to 20-40g/hr for their easiest days. And never more than 80g/hr for their longest days.

I’d like to see more people completely omit fueling on their coffee shop rides that are under 45 minutes. I have clients who come to me, fearing that they’re “doing something wrong” if they’re not having “something” during their recovery rides, even though they report feeling like they don’t need anything.

Likewise, I’d like to see those same people push 90-110g/hr on their 4-5hr z2 ride or their solo century attempt.

There should be massive jumps in fuel rates based on duration, and secondarily, based on intensity of activity, and I think people underdo those jumps, in both directions.

Pro cyclists are notoriously bad, on average, with their nutrition, and I think 15 yrs from now, we’ll see more widespread, high-carb fueling across the entire peloton. Pro cycling has some pretty intense “old school” thinking undercurrents in some areas. There is no lasting fat adaptation benefit from their carb restriction early-season. And there probably is a lasting detriment from having underfueled several months of training. (fatigue, reduced fitness adaptations to training)

Great question. No, they don’t.

The less lean a person is, the less likely it is that high-sugar fueling is optimal for their health.

The less total volume they do, the more they may actually benefit from high sugar fueling.

In terms of performance, they just can’t rely on the huge fat burning ability that comes with high volume endurance training. But also the more careful they’ll need to be with managing their kcal off the bike because if someone is only training 3-4 hours a week, it’s not wise to eat like the trash disposal that a 15-30hr-per-week person can.

If you mean how do they respond in terms of training effect acutely, I think the effects are more universal here. People can, in general, handle more carbs and benefit from them, in a single event or training session, than most people think. Substantially more, in most cases, if the hydration plan and fueling plan is on point.

Hence, I finally slashed my client load and Michelle (wife) and I are writing the app that’s going to take care of this for everyone, because I’m tired of only being able to reach a small handful of folks.

Actually… you seem to be very thoughtful and like someone who could offer good criticism to the math within the app. Would you be interested in beta testing? I just shot you a DM. It’s well before public release but I have a handful of folks who are testing it daily now.

Only requirement: you don’t hold back and tell me what you really think, at least once while you try it out. :slight_smile:

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Any study or data on that because I’m asking myself similar things at the end of that post:

Any thoughts?

Louise Burke has 2 awesome papers on this. (maybe more now, haven’t looked recently)

Here’s her 2020 PDF:

BURKE 2020, Crisis of Confidence Averted, Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible.pdf (2.0 MB)

She’s a legend. She deserves much more acclaim that she gets. I believe she was very pro fat adaptation type training and nutrition intervention 15 yrs ago, and has since been digging in hard to examine truth.

@redlude97’s post in that thread is a good summary of my understanding, too, if I’m reading correctly.

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That is a great post, and everybody with questions about fueling should read it.

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Lol this.

This is mostly what I was trying to express in the other thread. I don’t do fasted rides on purpose but regularly ride with little or no carbs mainly due to convenience. 1 hour commutes, pound some coffee and hop on the bike. Been doing it for almost a decade without an troubles. Pound sugar on the way home when I generally ride harder and can make proper mixed bottles.

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