In January last year (2023) we published a three blogs on Fructose over-consumption and consideration for endurance athletes. This includes both training, performance, gut-resilience and chronic disease risks.
Our perspective so far-
First our Part 1 blog highlighted the growing consumption of fructose (and sugar alcohols) and implications (see medical and research videos in blog) for chronic disease.
In our 2nd blog, we summarized the impact of high fructose consumption on blunting aerobic development, specifically its detraining effect on muscle and mitochondrial modelling from exercise training.
And finally, a 3rd blog we covered the impact that high Fructose consumption has on Gut integrity, resilience and stability.
These 2023 articles were less about race-day fructose consumption, but more about 'daily high-fructose consumption'.
Aside from general rise in sugar and fructose consumption (see below), recent promotion of 'excessive high-carb' (>100Gr/Hr) fueling only exacerbates the risks of fructose-over consumption in athletes.
For the record,
- SFuels does NOT add Fructose to any of its everyday training products, recovery products, or high intensity training-racing drink products.
- That said, SFuels does include Fructose in its race-day Gel, and positions its use in combination with its Non-Fructose race-day drink product.
- Finally, SFuels has talked through (Video) the science of the 'energy-oxidation' ceiling or cap of glucose, and the upside of adding Fructose for highest intensity (Zone 5 etc.) exercise.
Quick reset on Caloric Sweetener Trends
Regardless of industry and government interventions consumption of 'caloric sweeteners' continues to rise. Over the last 200 years, USDA data would show that consumption has grown by 1700%, to over 100 pounds per year per person. This translates today, to around 30 teaspoons of sugar per day.
For clarity here the measurement of 'caloric sweetener' consumption by the USDA Economic Research Service uses the following groupings, 1) refined sugar (i.e. processed sugar cane), 2) corn based (i.e. high fructose corn syrup, glucose syrup, Dextrose), 3) Honey, and 4) other edible syrups. For clarity, sugar cane (sucrose) is 50% Fructose, high-fructose corn syrup is 42-55% Fructose, and Honey is 21 to 42% Fructose.
Looking at the last 56 years (USDA) of data available, you can clearly seee where the majority of consumption growth (and issues) come from. The magnitude of growth in high-fructose syrup (HFCS) use in foods and drinks, is a quantum higher than all other sugar sources.
Aside from the downsides of high fructose consumption referenced in our earlier blogs, promotion of very high-carb consumption is irresponsible. The classic 2:1 ratio (Glucose to Fructose) in sports drinks, gels, gummies and advocacy for high (>100Gr/hour) carbohydrate intake is largely commercial driven. Articles of scientific review, from sports scientist and super-coach Dr Dan Plews question the evidence (performance) behind excessive carb intake. His argument is even more pronounced, for the majority of middle-back of the pack age-group athletes. But most concerning is the longer-term health implications for daily high-intake of fructose. We covered some of this in Part 1 Blog, but here's some further recent references.
New research: Fructose and Chronic Disease
Further to the issues and recommendations given in earlier blogs and videos, we wanted to provide some further research references regarding the on-going concerns of daily chronic fructose consumption.
As referenced in our 3-part blog series Robert H. Lustig, M.D., M.S.L., the Professor emeritus of Pediatrics, Division of Endocrinology at the University of California, San Francisco, presented a keynote (video) on the correlation and plausibility between Fructose over consumption, metabolic syndrome and cancer. Important to note, Fructose is specifically transported passively across membranes by a transporter known as GLUT5. Research studies have referenced the heightened expression of the GLUT5 and cancer outcomes. Since 2020, over 50 papers on pubmed have been focused on GLUT5 and cancer, with research growing since 2011. In an August 2024 review, researchers published their consolidated findings on GLUT5 over-expression and tumorigenic implications.
In an interesting study (all be it on animals) in January 2024, it was shown how the formation of Metabolic Syndrome could be invoked by Fructose and Uric Acid (a by product of fructose metabolism). The animals with Metabolic Syndrome, were then grouped into either, no treatment group, treatment with irisin (a protein produced by muscle, by muscle contractions) group, or treatment with Irisin and exercise group. The group receiving irisin and exercise treatment, reversed the markers of metabolic syndrome. Metabolic Syndrome is typically diagnosed (by a general practitioner) with three of these five conditions being present - Abdominal obesity, High blood pressure, Impaired fasting blood glucose, High triglyceride levels and Low HDL cholesterol.
Takeaways to Consider
1) SFuels continues to advocate for the healthier alternative (see 2-3-4 below) of fueling, by avoiding the over-consumption of carbohydrate (notably Fructose) by athletes in everyday training blocks.
2) SFuels advocates, the potential to incrementally maximize aerobic development and adaptions through Zone 2 training methods and Zone 2 fuel-substrate - and that this remain the core (70-80% of volume/time) of endurance athlete training programs.
3) SFuels advocates, that the inclusion of race-specific high-intensity workouts can be well supported with Fructose-free carbohydrate based fueling.
4) SFuels advocates, choosing better food options with low-fructose characteristics for lowering overall fructose intake in the interest of supporting optimal performance, gut-resilience and lowered chronic disease risk.
