Theories suggest that grape juices have the potential to reduce the risks of stomach bugs even in the germ-filled months of the year. Grape juice helps in changing the pH or acidity level in stomach acid resulting in stopping pathogens from multiplying. The antiviral properties of grape juices help in reducing the pH and acid level increase in intestinal tracts and keep a balance in the Vitamin C content in the stomach, leaving it healthier and cleaner.