Substrate Digest

A short issue, three studies, on the difference between a result and a finding. The thing that separates them is almost never the size of the effect. It is whether anybody said in advance what would count.

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A special issue on intermittent fasting. Eight papers from the last two years on a single methodological fact that runs underneath the whole field: measured against usual diet, fasting produces large effects with high certainty, and measured against a matched calorie restriction, most of them disappear.

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Seven papers, from 2023 to 2026, on whether the bacteria in fermented food can pick plastic particles out of a gut. Nothing here digests anything: the particles stick to the outside of the cells and leave unchanged. What the labs cannot agree on is whether that sticking is why any of it works, and one group tested the idea directly and ruled it out.

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Nine studies from the second half of August. Ten competing definitions of a healthy diet agreed on eighteen people out of six thousand, a plain count of food groups beat the elaborate index built to replace it, and the standard way of measuring what gut bacteria make turns out to be two different numbers added together.

Read the full issue on substratedigest.com, with every study, its source link and the "what this does not show" notes.

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A special issue on metabolic plasticity. Eight papers from 1983 to this year on how fast skeletal muscle rebuilds itself around whatever fuel it is given, why building up one pathway means turning the other one down, and what that trade costs when the two directions run on different clocks.

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A special issue on one question: which parts of the carbohydrate loading protocol actually matter. Eight papers from 1981 to this year, including the only meta analysis of loading protocols that exists, the closest thing to a head to head comparison of depletion against a taper, and a count of how many performance trials were ever blinded.

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Six studies from the first half of August. The birth canal loses most of the credit for an infant's first bacteria, ten days of heat training deliver everything except the two things it is usually done for, and a creatine trial that the authors themselves refuse to let you read as a brain result.

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Nine studies from the second half of July, and six headlines checked against the papers underneath them. A ketone drink that worked in the heat without cooling anyone down, caffeine evidence built almost entirely on men, and three papers where a marker moved and the outcome went unmeasured.

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Three months of cold water immersion after lifting left redox gene expression and mitochondrial enzyme activity exactly where the control group left them. It is the first issue where oxidative stress is one of our standing subjects.

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Nine trained cyclists who let themselves get 2.8% of body mass down burned about 16% less of the glucose they drank, with no warning sign from the stomach at all. Also this week: a reported carbohydrate gap in female athletes, a Science review on sugars and the human brain, a plant based performance null, and a quiet week for gut science with one probiotic trial to show for it.

Read the full issue on substratedigest.com, with every study, its source link and the "what this does not show" notes.

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