Lotus seeds are the seeds of the water lotus, Nelumbo nucifera. They have been used for centuries in Southeast Asian cuisine, and they have traditionally played an important role in Traditional Chinese Medicine (TCM), where they are known as lien zi. They are popular in Chinese desserts and soups, with some traditional recipes for events like the New Year calling for them in a variety of forms.
The seeds of the lotus form inside a distinctive seed head. When lotus seeds are harvested green, before they have fully matured, the bitter germ of the seed is carefully removed, as is the membrane which surrounds the seed. When dried, these seeds are sold as white peel lotus seeds, since they have a creamy white color. When seeds are allowed to mature all the way, they are sold as brown peel seeds, with the brown membrane intact. These seeds are split to remove the germ.
Fresh lotus seeds are sometimes sold inside the seed head, with consumers understanding that they need to remove the germ if they do not want a bitter surprise. Typically, people remove the rubbery membrane which surrounds each fresh seed before eating the seed, grinding it into a paste, or cooking it in syrup to make candied lotus seeds, a popular snack in some parts of Asia.
Dried lotus seeds are usually soaked overnight before they are used. Some common uses for the seeds include desserts, in which case the seeds are ground to make a paste, along with soups, rice porridge, and some stir fry dishes. Lotus seed paste is immensely popular in desserts in both China and Japan; in many regions, it is possible to find steamed dumplings filled with lotus seed paste.
In TCM, these seeds are said to be cooling, and they act on the spleen, kidney, and heart meridians. People use the seeds to treat diarrhea, heart problems, and insomnia, among other things. The bitter germ is also used in TCM to treat some heart conditions. Other parts of the lotus plant may be used as well, including the leaves and stamen.