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Fructose – The Worst of the Worst


I'll preface this by saying that in nearly 40 years in the health food/sports supplement & fuel industry, including almost 24 years employed at Hammer Nutrition, I honestly don't think there's a sports nutrition company that spends anywhere near as much time and energy promoting overall health as they do their products (and the constant push to sell those products).

A longtime friend of Hammer Nutrition once wrote, "An endurance athlete is a healthy person first, an athlete second, and an endurance athlete third." I think that's spot on regarding why we place so much emphasis on overall health. That's why you've seen more and more articles about healthy eating practices, what to avoid (e.g., artificial ingredients, excess sodium, processed seed oils), and more. You must be healthy to accrue any benefits in your workouts and succeed in your competitions.

And, over the 36+ years of Hammer Nutrition's existence, we've talked LOTS about the harmful effects of sugar on your health and athletic performance. These days, however, as there seems to be a revival in the odd and almost universally failed practice of trying to consume as many carbohydrates as possible (using fructose as part of the formula), it’s time for a discussion on what we feel is the worst thing you can put in your body in terms of health and athletic performance—fructose.

When one looks at even a fraction of the superabundant research on fructose and its adverse effects on human health, there should be no doubt that this is a substance you want to avoid at all costs. The beginning of just one research paper lays it out quite clearly,

"The increased consumption of fructose in the average diet through sweeteners such as high-fructose corn syrup (HFCS) and sucrose has resulted in adverse outcomes in society, producing considerable economic and medical burden on our healthcare system. Ingestion of fructose chronically has contributed to multiple health consequences, such as insulin resistance, obesity, liver disorders, and diabetes [1]."

Another negative health issue associated with fructose intake is uric acid (UA) production, with elevated amounts leading to gout, which Dr. Bayne French appropriately states, "is a truly painful condition." However, elevated uric acid levels are not just associated with gout. In his article, Uric Acid and its Metabolic Effects, Dr. French writes that elevated UA "drives the formation of insulin resistance, elevated blood sugar, type 2 diabetes, heightened blood pressure, distorted cholesterol, systemic inflammation, and weight gain. It is directly implicated in a large percentage of all-cause mortality, especially from cardiovascular disease."

According to Dr. French, the bottom line is that "on its own, elevated uric acid corresponds with disease."

While uric acid is also produced from alcohol and purines, it's not much of a stretch to suggest that the primary "source material" is fructose. One reason is that fructose intake has been on the rise for decades. One piece of research showed that fructose intake per person increased by approximately 32% from the 1970s to the early 2000s. [2]. Given the increasingly ubiquitous nature of fructose, as well as predicted dietary habits (i.e., higher fructose consumption), it’s a given that fructose intake must have increased above 32% in the past 15-20 years.

The other reason fructose is most likely the overwhelmingly leading candidate for uric acid production comes from another study where fructose consumption by 21,483 people, ages ranging from 2 to 71+, was analyzed. The results shows that the mean fructose consumption was estimated to be an astounding 54.7g/day (range 38.4g/day – 72.8g/day), accounting for an eye-opening 10.2% of total caloric intake. Consumption was highest among adolescents (12–18 years) at a whopping 72.8 g/day (12.1% of total calories); One-fourth of adolescents consumed at least 15% of calories from fructose [3]. Given that many of the study subjects were younger and probably not drinking much, if any, alcohol or consuming purine-rich foods, it would seem obvious that the likely candidate for uric acid production is fructose.

One vital thing to note, made very clear in Dr. French's article, is that elevated uric acid and gout are associated with sugar-sweetened beverages but not whole fruit consumption. Research has also shown this to be true regarding, for example, coronary heart disease (CHD). A study published in The American Journal of Clinical Nutrition [4] concluded: “Intakes of TGE (glucose monosaccharides, disaccharides, and starch), total sugar, added sugar, and fructose from added sugar and juice were associated with higher CHD risk, but TFE (fructose monosaccharides and sucrose) and fructose from fruits and vegetables were not.”

Lead researcher Dr. Kristine K. Dennis summarized, “For prevention of CHD, diets emphasizing whole fruits and vegetables while limiting added sugars and refined starches should be encouraged. Our research aligns with other evidence that whole fruit appears to have a protective role, regardless of fructose content. At the same time, it also aligns with other evidence suggesting that carbohydrate quality is important for cardiovascular disease risk."

Fructose in energy fuels? Why? Why?

Everything written up to now is a “drop in the ocean" regarding the information and research that shows the negative health issues associated with fructose intake from sources aside from whole fruits and vegetables. The bottom line is that we all know, or should know, that fructose is just flat-out bad for health. So why are companies still using this unhealthy substance in their energy fuels marketed to athletes? If fructose is so bad for your general health, how can it improve your athletic performance? I believe that fructose maintaining its position as an integral part of some company’s energy fuels goes hand in hand with the "rebirth" of the concept of taking in more and more and more calories during exercise via carbohydrates. In my opinion, the people/coaching organizations/companies promoting this must be looking back several years to studies done using various carbohydrate sources solo or in combination. The big thing now, as it was quite a few years ago, is the idea that combining different types of carbohydrates allows for greater amounts of calories to be available for energy production.

The "superiority of multiple carbohydrates" argument is based on glucose (maltodextrin as well) being absorbed by one transporter (SGLT1) and fructose by another transporter (GLUT-5). My issue with that is osmolality (never mentioned in any of the studies). When you combine simple sugars and complex carbohydrates, as some of these other companies' fuels do, the mixture's concentration and osmolality change dramatically to the point where neither carbohydrate source is digested efficiently. If this is the case, why would using two different transporters matter?

The other thing that no one seems to look at in these studies is the pace/intensity of the participants. Here is but one example:

G. A. Wallis, D.S. Rowlands, C. Shaw, R. L. Jentjens, A. E. Jeukendrup, Oxidation of combined ingestion of maltodextrins and fructose during exercise. Medicine and Science in Sports and Exercise 37 (3), 426-32 (March 2005).

In this study, eight trained cyclists performed three bouts of exercise, each lasting 2.5 hours, all at an intensity of 55% maximum power output. The cyclists consumed a maltodextrin-only drink (1.8 grams per minute), a maltodextrin/fructose drink (1.2 grams of maltodextrin + 0.6 grams of fructose per minute), or water. The results showed that carbohydrate oxidation (energy output) was most significant with the maltodextrin/fructose combination, peaking at 1.5 grams/minute (360 calories/hour).

COMMENT: What stands out is the low intensity of exercise: 55% of maximum power output is a recovery pace at best. Does it matter if oxidation rates were higher using a maltodextrin/fructose combination? When exercising at an intensity that low, it's not all that difficult to believe that the athletes could consume a massive 432 calories an hour—whether from maltodextrin only or a combination of maltodextrin and fructose—and not suffer stomach issues.

The real question is, “What would happen if the intensity of exercise increased to even a moderate rate/pace?” According to exercise physiologist Dr. Carl Foster, "The frequency of abdominal complaints and symptoms during high-intensity or competitive exercise (Brouns et al., 1987) suggests that attempting to feed while the gastric emptying rate is suppressed by high-intensity exercise may be inherently futile.” In other words, the gut works hard enough to process calories during exercise. Trying to jam down more calories—in the hopes of replacing what you're burning in equal or near-equal amounts—places a tremendous burden on the gut, which will always result in unpleasant, performance-inhibiting-to-ruining issues.


Fructose consumption and its adverse effects on human health—including the severe issues of excess uric acid production—are well documented in abundant scientific research. Aside from consuming whole fruits and vegetables, fructose is a substance to avoid. I'm in total agreement with the sound advice of Dr. French, "Eat sugar on rare occasions, in small amounts, and with mindfulness. Next, never drink sugar or fructose." You should be as well.

You will also want to avoid fructose when fueling your body during exercise. While some companies rely on the multi-carb studies to defend their inclusion of fructose in their fuels, the fact is that unless you plan to casually jog-walk your next marathon or soft-pedal/coast your next century ride, you can expect to experience any number of stomach distress issues when using fructose in the fuel you’re consuming.

Additionally, while some companies tout fructose as a "slow-burning" carbohydrate, courtesy of its low Glycemic Index (GI) of approximately 19 to 25, GI that low makes fructose more of a “no-burning” carbohydrate. More importantly, in the words of Dr. Robert Lustig, “Yes, fructose has a low glycaemic index of 19 because it doesn't increase blood glucose. It's fructose, for goodness sake. It increases blood fructose, which is way worse. Fructose causes seven times as much cell damage as glucose because it binds to cellular proteins seven times faster and releases 100 times the number of oxygen radicals (such as hydrogen peroxide, which kills everything in sight).”

Given all the negatives associated with fructose—all short-chain carbohydrates (“simple sugars”), actually—it’s no surprise that we remain convinced that the ideal carbohydrate source for athletes engaged in moderate-to-high intensity training and racing is complex carbohydrates (maltodextrin) only. It's why we formulate Hammer Nutrition fuels the way we do. For more than 36 years, tens of thousands of athletes have enjoyed better workouts and race results—without uncomfortable GI distress—using Hammer Nutrition fuels and adopting our protocols. Put our fuels to the test against anything else out there, and we guarantee that you will, too.



thank you for using science over marketing & cost to develop your products, that is why I am a life long Hammer customer.
Hammer Nutrition replied:
Hello Marian, thank you for your comment, decades of support and a valued member of the Hammer Family. BDF

Marian DeSimone

Great information !

Carol Williams

Sorbitol is difficult for anyone who has IBS irritable bowel syndrome, among other problems. Anything with polyols (FODMAP - fermentable oligo, di-, and monosaccharides and polyols) has to be eliminated when a person is enduring pain from IBS, fructose malabsorption, and other problems. Eliminating sorbitol from your food would make it more attractive to these people.
Hammer Nutrition replied:
Hello Joan, thank you for your feedback. Our FIZZ product is the ONLY one we make with any sorbitol in it and is unfortunately a necessary evil because the product will not dissolve without it. We make electrolyte product without any sorbitol in both capsule and powder form. From my decades of experience working with athletes who have IBS, eliminating wheat and other glutenous grains, along with refined sugars, especially fructose ensures the best results. BDF

Joan Crowe

I really enjoyed this article and your last article talking about cholesterol, blood sugar and statins. Keep the good content coming.
Hammer Nutrition replied:
Thank you for the positive feedback on the articles, Kevin! We’ll keep them coming!


Hi, as a cyclist and type 1 diabetic for 50 years now, this sort of article is of great interest to me. As a type 1 diabetic, regulating my blood glucose during exercise takes on a greater level of importance and is more complicated than it is for non-diabetics. Of course it is very hard for me to say scientifically that different sports gels and drinks are better or worse based on the mix of sugars they contain. However, in my own case, it seems to me that my blood sugar during exercise over 30 minutes in tempo, threshold and aerobic zones remains is more consistently in the right range when I use products that contain a mixture of fructose and other sources of carbohydrates than those that contain no fructose. It seems logical to me that for non-diabetics a similar response would also be true so I don’t want to make this a debate entirely about Type 1 diabetes.

50 years ago I recall being told that when my blood sugar was low (below 70mg/dL), straight glucose works faster than fructose to remedy the situation so always carry glucose tablets. So it was odd to me that some of the pricier and newer gels and drinks were using fructose. It seems counter-intuitive that this would help regulate BS better during intense exercise. It may have something to do with how continuous glucose monitors determine actual BS from body fluids and that the issue is actually the way CGMs work. To be sure, I would need to stop during exercise and take actual BS readings via finger pricks. This is an area I would love to see more research since many Pro cycling teams are using CGMs now and the rile of thumb is that they lag actual BS by upto 20 minutes.

In any event, I find this statement to be misleading, incomplete or somewhat out-of-context: “there should be no doubt that this is a substance you want to avoid at all costs” . As you go on to quote , this is referring to ’ average diet through sweeteners such as high-fructose corn syrup AND sucrose. So to say “[fructose] is a substance you want to avoid at all costs” in an article aimed at athletes who use your products is incomplete at best and irresponsible at worse.

I have user hammer products for a long time and will continue to do so for a number of reasons and appreciate such articles but I do object to the way this topic is presented.
Hammer Nutrition replied:
Hello Andrew, thank you for your comment, but I will have to respectfully completely disagree with you. Over the past 35 + years, I have helped type 1 diabetics accomplish amazing things like the first Iron distance triathlon, 3 person team doing Race Across America, solo of the same and many others to list here. Fructose should NOT be consumed voluntarily, unless it’s in the form of whole fruit, by anyone, whether they are type 1 or 2 or functioning pancreas, especially if they are active and training many hours per week. We’ve provided more than enough evidence of this truth and will continue to do so in future editions of ENW. The massive and cumulative damage to one’s metabolic health from consuming this form of sugar simply can’t be denied. If you choose to consume processed, refined fructose while you exercise, that is certainly your prerogative, but you’ll have to use products other than Hammer. BDF


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