Hello Nature readers,
Today we gain insight into why eating less slows ageing, find that politics might be causing an academic brain drain in the southern United States, and enjoy games and seasonal science songs in the Nature Podcast.

We’re taking a break for the holidays, but never fear! I’ll be popping back into your inboxes with two special editions on Thursdays for the next two weeks. Then we’ll return to our usual routine on Monday 6 January. Happy holidays!

Why eating less slows ageing

A component of bile called lithocholic acid, which is made by gut bacteria and helps to digest fat, can extend the lifespan of some animals. Researchers found, in mice, that levels of the acid rise during calorie restriction and that it activates a protein called AMPK — which scientists have already linked to the health benefits of eating less. When the team fed lithocholic acid to nematodes (Caenorhabditis elegans) and fruit flies (Drosophila melanogaster), the animals lived significantly longer than those that had not been given it. There is no evidence yet that taking lithocholic acid would have the same effect in humans — and at high doses, it could be toxic.

Southern scientists face political problems

A survey of faculty members working in US southern states suggests that the political climate is hitting morale among academics and driving a brain drain away from the region. Nearly 3,000 self-selected participants cited diminished academic freedom, restrictions on reproductive healthcare, harassment and the erosion of support for diversity, equity and inclusion programmes. “Multiple faculty members at my institution have been doxxed and harassed, including by elected officials,” wrote one female instructor in Texas. “This makes it difficult for me to do my job or feel safe on campus or at home and honestly just live my life.”

Stem cell therapies creep toward the clinic

The flurry of more than 100 clinical trials exploring the potential of stem cells to replace or supplement tissues in debilitating or life-threatening diseases is a turning point for the field after stretches of ethical and political controversy. For now, the trials are small and focussed on safety. Problems such as defining which cells will be most fit for which purposes still need to be solved, but stem-cell therapies for diseases from heart failure to diabetes are moving forward. Some researchers think stem cell therapies could enter the clinic in the next five to ten years.

Find your place with an industry postdoc

Last year, a Nature survey of postdoctoral researchers found that those who work in industry tend to be better compensated and have greater job satisfaction. Nature spoke to three postdocs who work at large pharmaceutical and life-science companies — Genentech, Merck and AstraZeneca — about the transition from academia and the opportunities that industry has to offer. “I’m well-funded and taken care of,” says postdoc Annie Woolven at AstraZeneca. “I have a standard working week. After working practically 24/7 on my PhD thesis, it’s a welcome change of pace.”

Podcast: Festive spectacular 2024

Games, seasonal science songs — and even a bit of science news — feature in this year’s holiday-themed Nature Podcast. Plus, I was invited to join a very enjoyable, but clearly rigged, quiz on some of the biggest stories of the year.

Futures: Science fiction from Nature

Two partygoers find each other in every universe in In the space between seconds.

Five best science books this week

Andrew Robinson’s pick of the top five science books to read this week includes survivors’ stories of the 1945 US atomic bombing of Hiroshima and an exploration of the “scary and disquieting” — but plausible — idea of reviving a brain, preserved by freezing, in the far future.

How food shapes self-image

In Eating and Being, historian Steven Shapin explores the idea that ‘you are what you eat’ and how philosophies of food have shaped the Western sense of self. His central idea is encapsulated in the book’s last lines: “In the past, knowledge about what we eat belonged to knowledge about who we are. It still does.”

A wake-up call about women’s mental health

Psychiatrist Linda Gask meticulously exposes and dismantles many deep-seated biases about women’s mental health in Out of Her Mind. From eating disorders and maternal mental illnesses to menopause and age-related dementia, the misconception that women frequently fabricate or exaggerate their symptoms can lead to poor health — and even loss of life — for women, and huge costs for society and health-care systems.