Probiotics - used in everything from chocolate to baby formula for gut health - might not be as effective as we think according to new research.

Through a series of experiments looking inside the human gut, Israeli researchers have shown how many people's digestive tracts prevent standard probiotics from successfully colonising them.

Professor in the Immunology department at the Weizmann Institute in Tel-Aviv and lead author Eran Elinav told Larry Williams the pro biotics are ineffective to many people who consume them.

"They don't work when they are given universally, some people are completely resistant while others accommodate them."

LISTEN ABOVE AS ERAN ELINAV SPEAKS TO LARRY WILLIAMS