Outcomes/ effect of mixed feeding?

[SleepBecomesHim321]

Hi all, I was wondering if anyone could point me towards some robust research into the difference in health or other benefits between bf exclusively and mixed feeding (50:50). I've seen the LLL and other websites but I'm interested in what difference, if any, there is between these two approaches If you bf for 50% of time, what difference will it make to the baby if ff the other 50% of the time? Baby is 4mo, EBF until now.

Thanks.