Pineapple juice contains the enzyme bromelain, which is a natural anti-inflammatory agent and digestive enzyme. Bromelain helps reduce inflammation and pain following surgery and encourages the healing of bruises, according to New York University's Langone Medical Center. It may also help reduce inflammation caused by sinusitis. As an enzyme, bromelain promotes good digestion by helping the body break down proteins.

A 1-cup serving of canned pineapple juice supplies almost 30 percent of your recommended daily allowance of vitamin C. If it has ascorbic acid added, you'll get more than 100 percent of your daily allowance. Vitamin C functions as a natural antioxidant and helps keep your immune system healthy. Your body body can't make collagen without vitamin C. Collagen is a protein used to build bones and to make connective tissues that strengthen and support your skin, blood vessels, tendons and ligaments. Vitamin C also helps the body metabolize fats and produce neurotransmitters, according to the Linus Pauling Institute. 

One cup of pineapple juice contains 11 percent of your recommended daily allowance of folate and 19 percent of vitamin B-6. Both of these vitamins help reduce levels of homocysteine in your blood. High levels of homocysteine increase your risk of developing cardiovascular disease. Folate is essential for the synthesis of protein, red blood cells and normal growth and development. You need vitamin B-6 to make neurotransmitters that help regulate mood and to metabolize proteins.

Potassium is an electrolyte, which means that it carries an electrical charge. In this role, it stimulates nerve impulses and muscle contractions. It also helps regulate your heart beat. Another important job filled by potassium is its ability to lower blood pressure. Eating too much salt increases your blood pressure, but if you get enough potassium every day, it can help offset the damage from salt. Adults should consume 4,700 milligrams of potassium daily, but most Americans get barely half that amount, according to the U.S. Department of Agriculture. One cup of canned pineapple juice supplies 7 percent of your daily potassium.