Elderberries contain natural substances called flavonoids. They seem to help reduce swelling, fight inflammation, and boost the immune system. Limited studies have found that elderberry eases flu symptoms like fever, headache, sore throat, fatigue, cough, and body aches. Elderberry may have positive effects on some markers of heart and blood vessel health. Studies have shown elderberry juice may reduce the level of fat in the blood and decrease cholesterol. ... Elevated uric acid is linked to increased blood pressure and negative effects on heart health.