Carotenosis xanthaemia) is the presence of the orange pigment carotene in blood from excessive intake of carrots or other vegetables containing the pigment resulting in increased serum carotenoids.[1][2]:540[3]:681 Carotenoids are lipid-soluble compounds that include alpha- and beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin. The primary serum carotenoids are beta-carotene, lycopene, and lutein. Serum levels of carotenoids vary between region, ethnicity, and sex in the healthy population. All are absorbed by passive diffusion from the gastrointestinal tract and are then partially metabolized in the intestinal mucosa and liver to vitamin A. From there they are transported in the plasma into the peripheral tissues. Carotenoids are eliminated via sweat, sebum, urine, and gastrointestinal secretions.[citation needed] Carotenoids contribute to normal-appearing human skin color and are a significant component of physiologic ultraviolet photoprotection.[citation needed]