Sourness is caused by the taste of acids, such as vinegar in alcoholic beverages. Sour foods include citrus, specifically lemons, limes, and to a lesser degree oranges. Sour is evolutionarily significant as it is a sign for a food that may have gone rancid due to bacteria.
Many foods, however, are slightly acidic, and help stimulate the taste buds and enhance flavor.
Substances that support metabolism
Dietary minerals are generally trace elements, salts, or ions such as copper and iron. Some of these minerals are essential to human metabolism.
Vitamins are organic compounds essential to the body. They usually act as coenzymes or cofactors for various proteins in the body.
Water is an essential nutrient and is the solvent in which all the chemical reactions of life take place.
Main articles: Plant nutrition and Fertilizer
The strip of a green alga (Enteromorpha) along this shore indicates that there is a nearby source of nutrients (probably nitrates or ammonia from a small estuary).
Plants absorb nutrients from the soil or the atmosphere, or from water (mainly aquatic plants). An exception are the carnivorous plants, which externally digest nutrients from animals before ingesting them.