There is some evidence to suggest that pineapple juice may help reduce inflammation. Pineapple contains a compound called bromelain, which has anti-inflammatory properties. In one study, people with osteoarthritis who took bromelain supplements had less pain and stiffness than those who did not take the supplement. Bromelain may also help reduce inflammation in other conditions such as rheumatoid arthritis.
However, more research is needed to confirm the effects of pineapple juice on inflammation. If you're considering adding pineapple juice to your diet, talk to your doctor first to make sure it's safe for you.