The cooking process can affect the nutrient quality of carrots on multiple levels, according to Scientific American. First, the thick cell walls of plants are broken down when cooked. This allows the body absorb nutrients more easily than if they were left raw or bound by their tough cellular structures. However, carrots that have been boiled or steamed also have higher levels of antioxidants, especially carotenoids.
A 2008 study published in the Journal of Agriculture and Food Chemistry showed that cooked carrots had higher levels of carotenoids, which boost the immune system. A 2003 study published in the European Journal of Nutrition found that significantly more beta-carotene was absorbed when carrots were cooked and pureed than when they were eaten raw. Researchers agree that carrots can be preserved by boiling them. Also, steaming is a great cooking method.