During the winter months, here in the UK, days are short and there isn’t enough sunlight for most of us to make the vitamin D we need. Taking a tiny vitamin D supplement is a minute change that could have a huge impact on our health. Professor David Llewellyn from Exeter University explains to Michael that vitamin D helps clear abnormal proteins, such as amyloid plaques and tau, from the brain, which may help protect you from dementia. Having enough vitamin D can also boost your immune systems, making that common cold easier to recover from. It could even lift your mood! Volunteer Baljit tries making vitamin D a habit. Series Producer: Nija Dalal-Small Science Producer: Catherine Wyler Researcher: Sophie Richardson Researcher: Will Hornbrook Production Manager: Maria Simons Editor: Zoe Heron A BBC Studios production for BBC Sounds / BBC Radio 4.