Short-chain fatty acids (SCFAs)—especially acetate, propionate, and butyrate—are produced when gut microbes ferment carbohydrates that the human body cannot digest. Over the past decade, these small molecules have moved beyond being viewed as simple fuel. Instead, they are now recognized as signalling messengers that help tune metabolism, shape immune responses, and support physiological balance across organs. A new review in Nature Metabolism brings together scattered findings to clarify how SCFAs are made, how they are processed in the body, and why they matter for health.

The article emphasizes that SCFA production is not uniform. It depends on which microbial communities inhabit the gut, which dietary substrates reach the colon, and how microbes share resources through cross-feeding. When multiple bacterial species coordinate, fermentation pathways can shift, increasing the output of particular SCFAs. In that way, the “hardware” of the microbiome and the “inputs” provided by diet jointly determine the chemical signals generated in the intestine.

After their formation, SCFAs are handled by host tissues through absorption and further metabolic conversion. The review highlights that acetate, propionate, and butyrate can influence local and systemic physiology, helping link intestinal chemistry to whole-body regulation. Their effects are therefore both immediate—through signalling pathways—and longer-lasting—through changes in gene regulation.

Mechanistically, the authors focus on receptor-mediated communication. SCFAs activate specific receptors on immune and metabolic cells, altering inflammatory tone and metabolic signalling. This receptor layer helps explain how intestinal events can reverberate in distant tissues that rely on tightly controlled energy and immune states.

Beyond receptors, SCFAs also affect epigenetics. By influencing chromatin-modifying enzymes and related regulatory networks, they can change how genes are expressed without altering DNA sequence. Such effects provide a plausible bridge between diet–microbiome interactions and sustained shifts in health trajectories.

The review further surveys tissue-specific outcomes, from effects on gut barrier function to immune regulation and metabolic homeostasis. Importantly, this heterogeneity helps reconcile why SCFAs sometimes show protective associations while other contexts yield mixed results—differences in dose, timing, microbial ecology, and host physiology can all matter.

When the evidence is assembled, the paper argues that SCFAs are strongly implicated in metabolic health and disease risk. Conditions such as obesity, insulin dysregulation, and inflammatory disorders have been linked to altered SCFA profiles, though causality remains an active area of investigation. The authors also discuss the limitations of current studies, including differences in measurement methods and confounding dietary factors.

Finally, the review evaluates translational opportunities. Rather than treating SCFAs as isolated supplements, it frames dietary and therapeutic strategies around pathways that enhance beneficial SCFA production or mimic their downstream effects. With low fibre intake becoming a public health concern worldwide, the work positions SCFAs as a key biological rationale for improving diet quality.

Overall, this Nature Metabolism review synthesizes what is known—and what is still uncertain—about SCFAs as central mediators between gut microbes and host biology. It suggests that targeting microbial fermentation and SCFA signalling could become a practical lever for metabolic disease prevention.

Subject of Research: Gut microbiota–derived short-chain fatty acids and their physiological roles
Article Title: Short-chain fatty acids
Article References: Dagbasi, A., Cai, M., Hirdaramani, A. et al. Short-chain fatty acids. Nat Metab (2026). https://doi.org/10.1038/s42255-026-01579-9
DOI: https://doi.org/10.1038/s42255-026-01579-9
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A self-taught ornithologist, he won a MacArthur fellowship for his precise, resplendent illustrations that appeared in definitive field guides to tropical songbirds.

Two meteor showers will peak together overnight on Thursday, July 30, into Friday, July 31 — but skywatchers should expect a moonlit challenge rather than a dazzling display.

Both the Southern Delta Aquariids and the Alpha Capricornids reach maximum activity just one night after July's full Buck Moon, which turns full on Wednesday, July 29. According to the American Meteor Society, the moon will still be 98% full during the peaks of those meteor showers, meaning bright moonlight will wash out many of the fainter "shooting stars."

This year, the Southern Delta Aquariids are active from July 12 to Aug. 23 and peak on the night of July 30-31. The meteor shower can result in about 25 shooting stars under ideal dark skies, but the full moon makes this year's timing far from perfect. The Alpha Capricornids, which are active from July 3 to Aug. 15 this year, offer around five meteors per hour on the same peak night. That's not many, but the Alpha Capricornid meteor shower is known for bright fireballs — space rocks that shine brightly, and sometimes colorfully, as they catch fire during the plunge through Earth’s atmosphere.

From North America, the moon will appear bright for much of the night around the meteor showers' peak. A nearly full moon does not stop meteors from occurring, but it brightens the sky enough to hide the faintest streaks. That's particularly important for the Southern Delta Aquariids, which can be faint and typically lack fireballs, according to the American Meteor Society. Even still, the overlapping showers make a great night for practicing your meteor shower photography or for taking pictures of the moon.

The best time to try watching will be between midnight and dawn, when the radiant — the point from which the meteors seem to emanate — of the Southern Delta Aquariids, the constellation Aquarius, is highest in the southern sky. Observers in the southern U.S., Mexico and the Caribbean will be better placed than those farther north because Aquarius climbs higher at lower latitudes.

For the best chance of seeing some shooting stars, keep the moon behind you or blocked by a building, tree or hill, and look toward the darkest part of the sky. Meteor showers are always best viewed with the naked eye.

If you're clouded out — or mooned out — during the July meteor peaks, don't worry, as you'll get a better opportunity in August. The Perseid meteor shower will peak overnight on Aug. 12-13, just after the Aug. 12 new moon, when skies will be moonless for the meteor shower's peak rate of 100 meteors per hour.

That same new moon will also cause a total solar eclipse to be visible along a narrow path through eastern Greenland, western Iceland and northern Spain. A partial solar eclipse will be seen from parts of Canada and the northeastern U.S. (Remember to protect your eyes with proper solar eclipse glasses at all times during the partial phases.)

The combination of a solar eclipse and the peak of a major meteor shower will make Aug. 12-13 potentially one of the most exciting days of the year for skywatchers.

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