For eons, salt has been crucial to human health, culture, and diet. On this episode of The Evidence, we explore the strange science of salt taste – why it can be sweet, salty, or even a flavour enhancer. We look at how salt keeps our bodies running, and what happens if we have to little of it. And while too little salt may be bad, too much is also a problem. What does the science say about how much salt is optimal, and what can we do to make sure we’re eating the right amount? Claudia Hammond is joined by a panel of salty experts who will help find the answers to these questions and more.

Do YOU know what you're eating? Are you sure?

Dr Chris van Tulleken is keen to make good food choices, and buy the best chicken possible for his dinner. High welfare, tasty, and good for the environment, ideally. But it's not as easy as that. How CAN he make good food choices if he has no idea what he's buying?

Chris explores what we actually know about the food we buy, and to what extent we can trust what's on a label.

He also uncovers the startling truth about two very different ways that we buy chicken - lifting the lid on why sometimes, even the most moral meat shoppers turn a blind eye...

We’ve heard about the potential problems around chicken welfare. But how does that square with their impact on the environment?

Dr Chris van Tulleken finds out what it takes to produce the most eco-friendly chicken meat possible. And makes a devastating discovery. Welfare concerns, and environmental credentials, often pull in OPPOSITE directions. Does he want to eat the happiest birds, or the ones kindest to the planet?

Halfway through his poultry quest, Chris remains massively conflicted: he loves chicken, but some of what he’s discovered makes him question how much he eats it. Will he still be able to look at it the same way as he goes deeper down the rabbit hole? And more importantly, should he keep serving it up to the family?

We eat chicken. A LOT of it. We might love the taste, but what about how we're treating those birds?

After witnessing first-hand the reality of indoor chicken farming - how most of the chicken we eat is raised - Dr Chris van Tulleken wants to know: are the birds happy enough, or is our method of rearing cheap chicken actually cruel?

If so, what’s the ‘happier’ alternative – and do carnivores like Chris care enough to pay the price for that, or does a love of meat ultimately trump ethics?

Chris battles with his conscience, and finds the answer hard to stomach.

So we started farming this bird called chicken, and it spread around the world. But what does it actually TAKE to feed us the amount of chicken we want to consume?

100 years ago this was a scrawny, egg-laying bird, only good for a stew once her eggs ran out – no one ate chicken meat. Fast forward to today and it’s the most consumed protein on the planet. How did we come to eat it in the first place, and what are the consequences of producing chicken meat on the vast, industrial scales we now consume it?

Dr Chris van Tulleken uncovers the extraordinary accident of history that birthed a new industry, and changed the way we eat – and think about – meat forever.

Dr Chris van Tulleken is on a mission to find out what we’re eating, why, and who or what might be influencing our decisions. And he’s starting his quest to uncover food truths with the most eaten meat in the world, and one of the most numerous animals on our planet: chicken.

He’s recently been forced to confront a serious gap in his food knowledge - what happens before it gets to our plates - and has decided this, the world’s most popular meat, is an ideal starting point.

Chris’ initial investigations reveal the vast scale of modern chicken consumption; and how a once revered jungle fowl was manipulated to become a modern food success story, a fast-growing heavy-breasted beast to feed the masses.

Now, he's torn: is this a triumph of human ingenuity – or the creation of a monster?

Dr Julia Ravey and Dr Ella Hubber both have a love of science, but it turns out there’s a lot they don’t know about some of the leading women at the front of the inventing game. In Unstoppable, Dr Julia and Dr Ella tell each other the hidden, world-shaping stories of the engineers, innovators and inventors they wish they’d known about when they were starting out as scientists. This week, the inventor whose incredible capacity to solve problems inspired today’s most popular period products.

Mary Beatrice Davidson Kenner – known as Beatrice – grew up in a family of inventors, creating her first invention at just six years old. And she didn’t stop there – she continued to invent throughout her adult life, including a new and improved sanitary pad in a time when there was still a big taboo around periods.

However, as an African American woman during a time of racial segregation, Beatrice faced injustice and discrimination when trying to get her inventions patented. But if anything, this spurred Beatrice on, and at one point in time she held the most patents of any African American woman.

Dr Julia and Dr Ella are joined by Professor Sharra Vostral and Ashleigh Coren as they tell Beatrice’s remarkable story.

Presenters: Dr Ella Hubber and Dr Julia Ravey Producers: Ella Hubber and Julia Ravey Assistant producer: Sophie Ormiston Production co-ordinator: Elisabeth Tuohy Editor: Holly Squire

In her last year of high school, Olga González-Sanabria went on a field trip to the University of Puerto Rico’s school of engineering – and immediately knew that was what she wanted to do. She followed her passion and after university was recruited by Nasa, where she carried out instrumental work, without which we would not have the International Space Station.

As the very first Latina woman working in engineering at Nasa, Olga’s career has not always been an easy ride, but is filled with remarkable achievements. Dr Ella and Dr Julia tell her story, and Olga herself gives us a first-hand account of her life so far.

Presenters: Dr Ella Hubber and Dr Julia Ravey Producers: Ella Hubber and Julia Ravey Assistant producer: Sophie Ormiston Production co-ordinator: Elisabeth Tuohy Editor: Holly Squire

(Photo: Olga González-Sanabria. Credit: Nasa Glenn Research Center)

Dr Julia Ravey and Dr Ella Hubber both have a love of science, but it turns out there’s a lot they don’t know about some of the leading women at the front of the inventing game. In Unstoppable, Dr Julia and Dr Ella tell each other the hidden, world-shaping stories of the engineers, innovators and inventors they wish they’d known about when they were starting out as scientists. This week, the story of an Indian chemist whose work laid the foundations to save thousands of lives.

In a lab in 1950s Kolkata, Asima Chatterjee laboriously extracts chemicals from the Indian snakeroot plant. She knows she’ll have to send the products away – she doesn’t have the money or resources to analyse them in India. But the tireless and uncompromising chemist perseveres, and her work paved the way for modern-day chemotherapy treatments.

Asima grew up in a time when it was uncommon for women in India to have an education, but went on to become a hugely influential figure in her field whose work is still repurposed and cited today. Dr Ella and Dr Julia take us through her inspirational journey, joined by Professor Sivapriya Kirubakaran and Dr Sarah O’Connor.

Presenters: Dr Ella Hubber and Dr Julia Ravey Producers: Ella Hubber and Julia Ravey Assistant producer: Sophie Ormiston Production Coordinator: Elisabeth Tuohy Editor: Holly Squire

Dr Julia Ravey and Dr Ella Hubber both have a love of science, but it turns out there’s a lot they don’t know about some of the leading women at the front of the inventing game. In Unstoppable, Dr Julia and Dr Ella tell each other the hidden, world-shaping stories of the engineers, innovators and inventors they wish they’d known about when they were starting out as scientists. This week, the story of the woman who mastered viewing the world in microscopic detail – ultimately helping us discover the structure of DNA.

Florence Bell’s scientific career began in the 1930s whilst studying at Cambridge University. The University didn’t grant degrees to women at the time, but this didn’t dissuade Florence. She was so talented at an imaging technique called X-ray crystallography that she started a PhD in the field – and it was during this time that she would make a pivotal discovery about the molecule of life.

Florence is an unsung hero of the DNA story. Her work laid the foundation for a vital field of research, yet her contribution was buried for years. Dr Julia and Dr Ella tell Florence’s tale, with input from Dr Kersten Hall, science historian and visiting fellow at the University of Leeds.

Presenters: Dr Ella Hubber and Dr Julia Ravey Producers: Ella Hubber and Julia Ravey Assistant producer: Sophie Ormiston Production Coordinator: Elisabeth Tuohy Editor: Holly Squire

(Photo: Florence Bell. Credit: Courtesy of her son Chris Sawyer. No reuse)

Dr Julia Ravey and Dr Ella Hubber both have a love of science, but it turns out there’s a lot they don’t know about some of the leading women at the front of the inventing game. In Unstoppable, Dr Julia and Dr Ella tell each other the hidden, world-shaping stories of the engineers, innovators and inventors they wish they’d known about when they were starting out as scientists. This week, the story of an engineer who turned plastic into gold, all starting from her mother’s backyard.

Every day, around 500 tonnes of plastic waste is generated in the Kenyan city of Nairobi. Hardly any of it is recycled – but engineer Nzambi Matee is on a mission to change that. Frustrated by the level of pollution, in 2017 Nzambi constructed a laboratory in her mother’s backyard. It was here that she used her self-taught engineering skills to convert plastic waste into bricks that are stronger and more eco-friendly than concrete.

Since then, Nzambi’s backyard operation has grown into a company – Gjenge Makers – and the bricks are widely used across Nairobi. And at only 31, Nzambi is just getting started. As Dr Julia and Dr Ella trace Nzambi’s journey, we hear from Nzambi herself about what it took to get to this point, as well as her ambitions for the future.

Presenters: Dr Ella Hubber and Dr Julia Ravey Producers: Ella Hubber and Julia Ravey Assistant producer: Sophie Ormiston Production Coordinator: Elisabeth Tuohy Editor: Holly Squire

(Photo: Nzambi Matee, Kenyan entrepreneur and inventor, holds plastic polymer recycled to make bricks. Credit: SIMON MAINA/AFP via Getty Images)