Seaweed has been a common ingredient in many Asian cuisines for thousands of years, and now science is revealing it could be one of the factors behind the impressive life expectancies in many of these cultures. As well as being incredibly nutrient-rich, a new study has shown that when seaweed is broken down in the gut, some sugars are produced which act as a prebiotic to help healthy gut bugs thrive. 4 That provides many health benefits, and can have anti-cancer effects in the colon.