Dietary acid refers to any substance that has a sour taste and is capable of causing an increase in hydrogen ion concentration when it reacts with water or other liquids. These acids are commonly found in foods such as citrus fruits, vinegar, tomatoes, and fermented products like yogurt and sauerkraut. In the context of human nutrition, dietary acid refers to the consumption of these sour-tasting substances that can have an impact on the body's pH levels, potentially affecting overall health and wellness.