Which of the following is not a type of phytonutrient?

Phytonutrients, also known as phytochemicals, are natural compounds found in plants that contribute to their color, flavor, and disease resistance. They play an important role in human health by providing antioxidant and anti-inflammatory benefits, among other effects.

Carotenoids, flavonoids, and lignans are all recognized categories of phytonutrients. Carotenoids are pigments found in plants that provide yellow, orange, and red colors, and are important for vitamin A production and vision health. Flavonoids are a diverse group of phytonutrients with antioxidant properties, found in fruits, vegetables, and beverages like tea. Lignans are a type of phytoestrogen found in seeds, particularly flaxseeds, and they have various health benefits related to hormone balance.

In contrast, proteins are macromolecules made up of amino acids and are not classified as phytonutrients. They are essential nutrients necessary for the growth and repair of tissues in the body, but they do not share the plant-derived characteristics or health benefits associated with phytonutrients. Therefore, proteins stand out as the only choice that does not fit into the category of phytonutrients.