Ascaris lumbricoides, the most common type of roundworm that infects humans, is a parasite and feeds on partially digested food in the small intestine of its host.

They don't have a mouth in the traditional sense, but instead have a large, muscular pharynx that they use to suck up the food. They are not picky eaters and will consume a variety of things, including:

* Partially digested carbohydrates

* Proteins

* Fats

* Vitamins

* Minerals

Essentially, anything that the human host has already begun to digest.

It's important to remember that Ascaris are not beneficial to their hosts and can cause a variety of health problems, including malnutrition, intestinal blockage, and even death in severe cases.