Dan Saladino hunts down that flavour we call 'bitter', and asks if bitterness is disappearing from our food and drink - and why this matters.

Bitter tastes are found all over the planet; wild leaves, fruits, vegetables and more. Bitterness is also charged with cultural and culinary meaning. It can be revered, sought after - but it is also a sign of toxicity, and is, it seems, increasingly being shunned.

Dan Saladino talks to Jennifer McLagan, author of the James Beard Award-winning book "Bitter: A Taste of the World's Most Dangerous Flavour", who begun her epic journey into bitter following a conversation about grapefruits. Journalist and science writer Marta Zaraska has been tracking the de-bittering of our food, and reveals her findings, including the 'holy grail' of the assault on bitter. He also seeks out bitterness in the wild with forager and wild food specialist Miles Irving, and discovers the secrets of the bitter gourd (also known as bitter melon or karela) within a food culture that still deeply values bitterness, in the company of food writer and cookery teacher Monisha Bharadwaj.

As Dan delves into the world of bitter flavours, he shares a bitter brew with Professor Peter Barham - author of "The Science of Cooking" - and visits the drinks laboratory run by cocktail experts Tony Conigliaro and Max Venning.

Tasting bitter leaves, crystals, digestifs and more along the way, Dan asks what we stand to lose if we lose the taste for bitter.

Presenter: Dan Saladino Producer: Rich Ward.