It's what's inside that counts. There's a lot of information circulating about what constitutes a healthy diet, with no true consensus about the best way to eat to improve our everyday well-being. For example, it's widely believed that genetics play the most significant role in our overall health. However, epidemiologist Tim Spector has spent years studying the importance of gut health. And as he explains to Linda Geddes, dietary diversity is crucial for warding off infections, combating age-related diseases and maintaining a healthy weight.