Olive leaf extract has been found useful in improving resistance to microbial infection. It contains significant qualities of phenolic compounds, such as oleuropein, oleuropeoside, and hydroxytyrosol, that have been shown to have anti microbial properties, as well as antioxidant power. These properties may protect against intestinal or respiratory infections. It has been shown that olive plant tissue can reduce plasma cholesterol, protect from heart disease, and inhibit platelet aggregation. The polypheols of the olive plant also have blood sugar-lowering properties.