Issue 01 · 29 July 2026

Two sugars beat one, even on an empty tank

A double blind crossover trial found a 2:1 glucose to fructose blend oxidized more of the carbohydrate athletes actually swallowed, whether they were fully fueled or two days into an energy deficit. Elsewhere this week, carb loading research turned out to be mostly unblinded, and at the IRONMAN Worlds it was logistics and nerves, not knowledge, that broke women's fueling plans.

8 studies 8 July to 29 July 2026 Listen on Spotify

In this issue

Randomised double blind crossover Published 13 May 2026, verified on PubMed. The paper drew press attention in late July. Cite the May date.

Glucose plus fructose kept its oxidation edge even in underfueled athletes

In a double blind crossover trial, a 2:1 glucose to fructose blend oxidized more of the ingested carbohydrate than glucose alone, and the advantage held after 48 hours on half energy intake. Better oxidation did not rescue performance after the deficit.

The Journal of Nutrition · Barney et al. · 13 May 2026 · PMID 42134413

carbohydrate endurance-fueling energy-availability

0.48g/min
exogenous carbohydrate oxidation with the 2:1 blend vs 0.39 g/min with glucose alone, p<0.001
Methodological review and commentary Date as listed in the digest; not independently verified at source.

Only 2 of 14 carb loading studies were properly blinded, and both found nothing

A methodological review of carbohydrate loading research found that only two of fourteen studies used a double blind placebo controlled design, and neither found a performance benefit. The weaker studies reported effects at roughly the magnitude expected from placebo.

International Journal of Sport · Jones et al. · 24 June 2026 · PMID 42342234

carbohydrate endurance-fueling research-methods

2of 14
carb loading studies were double blind placebo controlled; both found no performance benefit
Expert opinion (Current Opinion article) Date as listed in the digest; not independently verified at source.

Low FODMAP diets are being handed to athletes who may not need them

A Current Opinion in Sports Medicine argues that symptom severity, not habit, should decide whether an athlete restricts FODMAPs. Athletes with mild or occasional symptoms are likely better served by a more liberal FODMAP intake that supports gut integrity.

Sports Medicine · Scrivin et al. · 24 July 2026 · PMID 42496856

gut-health GI-distress fodmap fiber endurance-fueling

0trials pooled
expert opinion arguing FODMAP restriction should match symptom severity, not be a default
Human feeding study 27 July 2026 is the date of the Cornell Chronicle story; the journal publication date is not stated in the digest and was not verified at source.

Whether fiber helps may hinge on which strain of one gut bacterium you carry

Cornell researchers fed resistant starch to more than 50 people and sequenced their microbiomes at strain level. Different strains of the same species, Bifidobacterium adolescentis, responded to the identical fiber in opposite directions.

Microbiology Spectrum · Poole et al. · 27 July 2026

microbiome fiber gut-health

>50people
fed resistant starch; strains of one bacterial species responded in opposite directions
Convergent mixed methods, observational The digest lists July 2026 without a day; not verified at source.

Only about a quarter of women at the IRONMAN Worlds hit carb loading targets

Among female triathletes at the 2024 IRONMAN World Championships, only 6 of 23 reached the 8 to 12 g/kg carbohydrate loading guideline. Interviews found the gap was not knowledge but travel logistics, nerves, food access, and identity around eating.

European Journal of Sport · Fortis et al. · undefined July 2026 · PMID 42274547

female-athletes carbohydrate endurance-fueling GI-distress fiber

26%
of women (6 of 23) met the 8 to 12 g/kg guideline; mean intake 6.4 ± 2.1 g/kg
Narrative review Date as listed in the digest; not independently verified at source.

Four nutrition claims aimed at active women outrun their evidence

A narrative review examined four claims circulating on social media about female athlete nutrition. It found limited evidence behind several of them, but not for the rigid sex specific rules built on top of them.

Proceedings of the Nutrition · Matkin-Hussey et al. · 1 July 2026 · PMID 42383324

female-athletes general-nutrition energy-availability

4claims
examined; limited evidence for several, none for the rigid rules built on them
In vitro screen plus narrative review The digest lists 16 and 22 July 2026 for the two papers; dates taken from the digest and not verified at source.

Two new looks at sweeteners and the gut, and neither delivers a clean verdict

An in vitro screen found around 75% of 39 sweeteners altered the growth of at least one of 25 gut bacterial species. A separate narrative review concluded the evidence supports neither a uniformly harmful nor a uniformly safe verdict on artificial sweeteners.

Molecular Systems Biology (screen); · Xin et al. · 16 July 2026 · PMID 42514471

sweeteners microbiome gut-health general-nutrition

~75%
of 39 sweeteners altered growth in at least one of 25 gut bacterial species, in vitro
Narrative review Date verified

Microplastics reach athlete diets, but nobody has studied athletes directly

A narrative review raises dietary microplastic exposure in athletes, flagging packaged foods and bottled drinks as plausible exposure routes. The authors are explicit that mechanisms are plausible while direct studies in athletes do not exist.

Nutrients 18(14):2398 · 22 July 2026 · PMID 42514468

microplastics general-nutrition

0studies
direct studies of microplastic exposure in athletes exist to date, per the review