Some foods have medicinal properties. If they are sold as foods, they are usually available at a reasonable price from numerous merchants. If they are sold as drugs, they are sold only by pharmaceutical companies at inflated prices.
The consequences of classifying a food as a drug are formal testing of its medicinal properties by a regulatory agency, and standardization of its labels to include legally required information about the medicinal contents, their effects and side-effects, and the recommended dosage.