(d) Cooking leads to opening of the cells, which leads to extraction of nutrients Our body does not have the possibility to break down cell walls of vegetables and legumes effectively and without cooking much of the nutritional value remains undigested. When they are slowly heated under water, the pectin swells and is extracted by the water. The cell opens and becomes softer. As a result the vegetable becomes soft and may rupture and with that also nutrients become available during consumption.