The material used as gelatin in the production of Jell-O, marshmallows and gummy bears could be placed in a laboratory dish to grow out bacterial cultures; but it is extremely susceptible to being consumed by the organisms scientists want to study. Agar gelatin is more resilient; and that is why laboratories prefer agar as a culture medium in petri dishes -- clear, flat dishes used to grow particular microorganisms for the purpose of study.
Plant biologists sometimes want to isolate growing plants to study the effects of specific additives to the plants' development. Just as bacterial cultures grow well in agar, plant biologists use agar as a neutral medium. For plant studies or for bacterial studies, agar can be mixed with particular materials to study the effects of those materials on plants or to nourish a culture of one microorganism. Among those additives are sugars, proteins, some bacteria, animal blood and even chocolate.
Agar is used extensively throughout Asia and the Pacific for culinary purposes. Agar is used in jellies and jams, in pies and cakes, in custards and fruit gelatins, in soups, and in iced drinks. Agar has very little nutritive value on its own, with only a trace of carbohydrates, less protein and no fats. Consequently, it has hardly any calories, which is good news for those who are weight conscious about food additives. Agar does have a trace of omega-3 fatty acid, some trace minerals and a small amount of potassium.
Agar is not easily absorbed by the gut, and it absorbs water very easily in its powdered form. For these reasons, agar has been successfully used as a dietary supplement for people who suffer from constipation. Agar acts as a bulking laxative and as an intestinal lubricant; but there are some cautions about using agar frequently this way. It is believed agar might reduce protein and mineral uptake by the body, thereby depriving the body of some nutrients in the process of treating constipation.