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Letter: Maybe this is why fasting diets work

Published 23 July 2025

From Malcolm Hunter, Leicester, UK

In your look at the small intestine, you mention that overnight fasting causes the valve between its last section, the ileum, and the colon to close, leading to partially digested food being retained in the ileum. This results in a surge in microbial numbers and in the production of short-chain fatty acids, created by fermentation of fibre, that help shield the ileum’s relatively thin lining from penetration by bacteria, cutting the risk of inflammation(21 June, p 40).

I wonder if an extended version of this occurs in intermittent fasting, where food is consumed during a very restricted period each day. Could this possibly explain some of its health benefits?

Issue no. 3553 published 26 July 2025

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