Sugar, seed oils, and avoiding sickness: your health questions answered

The first person has been treated with a highly anticipated new gene therapy that aims to turn back the clock on ageing cells. The trial is aimed at retinal cells, with the hope that encouraging them to behave as if they were young again could improve sight in the affected patients. If it proves to be safe, it could open the door to a whole raft of therapies based on the emerging field of cellular rejuvenation. To understand more about this cutting edge research, Madeleine Finlay hears from science editor Ian Sample and from Paul Knoepfler, professor of cell biology and human anatomy at the university of California, Davis.. Help support our independent journalism at theguardian.com/sciencepod

Scientists often talk about the importance of flora and fauna to the health of our planet, but Dr Toby Kiers, an evolutionary biologist and founder of the Society for the Protection of Underground Networks, wants us to consider another force: fungi. Her work charting the planet’s vital underground systems has earned her numerous awards, including a MacArthur fellowship and a Tyler Prize for Environmental Achievement (sometimes called the ‘green’ Nobel). She tells Ian Sample about her work mapping fungal networks on the remote Palmyra Atoll in the Pacific Ocean, and what the research reveals about fungi’s often invisible role. Help support our independent journalism at theguardian.com/sciencepod

Men’s average testosterone levels have halved over the past 50 years, according to scientists who say society is facing a male fertility crisis. Rising levels of obesity and diabetes are expected to play a part, but the team behind the work suggest that environmental factors such as endocrine-disrupting chemicals – which can be found in various household items – and global heating could also be factors in the apparent striking decline. Ian Sample speaks to science correspondent Hannah Devlin to find out how the work has been received and what the researchers want to see happen in response to their finding. Help support our independent journalism at theguardian.com/sciencepod

In the last 50 years, Britain has lost an astonishing 73 million wild birds from its landscape, according to the British Trust for Ornithology. Habitat loss, pesticides, disease, cats and the climate crisis mean there are fewer birds than ever before. For children and young people it can be difficult to appreciate the scale of the loss due to a psychological phenomenon called ‘shifting baseline syndrome’, where each generation inherits a degraded version of the environment, and therefore doesn’t notice the overall decline. But Gen Z are bucking the trend. Thanks to social media and the Merlin Bird ID app, birding has become cool. To find out what we’re missing from the dawn chorus, and why young people are embracing birdwatching, Madeleine Finlay hears from the writer Robert Macfarlane and from Jess Painter, a member of the RSPB’s youth council. Help support our independent journalism at theguardian.com/sciencepod

Researchers claim they are closer to creating life from nothing after building tiny, quivering blobs that use lab-made DNA to feed, grow and multiply in a dish. To find out how significant this step is, and where scientists hope it will lead, Madeleine Finlay hears from co-host Ian Sample and from Kate Adamala, professor of genetics at the University of Minnesota. Help support our independent journalism at theguardian.com/sciencepod