Absorption of carotenoids

Dietary fats, libers, and other carotenoids have been reported to interfere with carotenoid bioaccessibility. It is clear that by their presence in the gut, lipids create an environment in favor of hydrophobic compounds such as carotenoids. When arriving in the small intestinal lumen, dietary fats stimulate bile flow from the gallbladder and therefore enhance the micelle formation, which in turn could facilitate the emulsification of carotenoids into lipid micelles. Without micelle formation, carotenoids are poorly absorbed a minimum of 3 g of fat in meal is necessary for an efficient absorption of carotenoids, except for lutein esters that require higher amounts of fat. ... 

Baskaran, V, Sugawara, T., and Nagao, A., Phospholipids affect the intestinal absorption of carotenoids in mice. Lipids, 38, 705, 2003. 

Riedl, J. et al.. Some dietary fibers reduce the absorption of carotenoids in women, J. Nutr, 129, 2170, 1999. 

The food matrix including its fiber and lipid content and concentrations of other carotenoids in the diet may influence the extent of absorption of carotenoid compounds. The relative absorption of lutein from a mixed vegetable diet was lower than from a diet containing pure lutein. A mixed preparation of lutein and zeaxanthin did not influence the absorption of P-carotene. 

Mechanisms of Intestinal Absorption of Carotenoids Insights from In Vitro Systems... 

An In Vitro Model to Study Intestinal Absorption of Carotenoids.370... 

Kurilich, A.C. Britz, S.J. Clevidence, B.A. Novotny, J.A. 2003. Isotopic labeling and LC-APCI-MS quantification for investigating absorption of carotenoids and phyl-loquinone Som kale (Brassica oleracea). J. Agric. Food Chem. 51 4877-4883. 

Carotenoids, also in micellular form, are absorbed into the duodenal mucosal cells by passive diffusion. The efficiency of absorption of carotenoids is much lower than for vitamin A, between 9% and 22%, and is subject to a large number of variables, including carotenoid type, the amount in the meal, matrix properties, nutrient status, and genetic factors. Once inside the mucosal cell, (3-carotene is principally converted to retinal by the enzyme p-carotene-15,15 -dioxygenase, the retinal being converted by retinal reductase to retindl and esterified, though it can also be cleaved eccen-... 

Rods et aL reported improved absorption of carotenoids following improved fat intakes in Ruanda (Roels et al., 1958) and in Indonesia (Roels et aL, 1963). In the Philippines, however, no correlation was found between dietary fat and xerophthalmia very few of the Filipino children (only 7%) consumed under 10 g fat per day (Solon et al., 1978). Jayarajan et al. (1980) studied 70 children 2-6 years of age in a low-income rural Indian community, where their habitual diets provided about 5 g of visible fat and 400 mg p-carotene daily. These diets were... 

Numerous factors affect the intestinal absorption of carotenoids. Digestion of food in the stomach increases accessibility of carotenoids for absorption by maceration in HCl and digestive enzymes. The acidic enviromnent of the stomach helps to disrupt cell walls and other cellular ultrastructure of raw fruits and vegetables and causes further breakdown of cooked foods to release carotenoids from food matrices in which they are contained or bound. 

The presence of other carotenoids can affect the absorption of carotenoids into intestinal mucosal cells, since carotenoids can compete for absorption or facilitate the absorption of another. Data on carotenoid interactions are not clear. Human studies show that /3-carotene decreases lutein absorption, while lutein has either no effect or a lowering effect on /3-carotene absorption. Although not confirmed in humans, the inhibitory effect of lutein on /3-carotene absorption might be partly attributed to the inhibition of the /3-carotene cleavage enzyme by lutein shown in rats. Beta-carotene also seemed to lower absorption of canthaxanthin, whereas canthaxanthin did not inhibit /3-carotene absorption. Studies showed that /3-carotene increased lycopene absorption, although lycopene had no effect on /3-carotene. Alpha-carotene and cryptoxanthin show high serum responses to dietary intake compared to lutein. In addition, cis isomers of lycopene seem to be more bioavailable than the -trans, and selective intestinal absorption of a)X-trans /3-carotene occurs, as well as conversion of the 9-cis isomer to sW-trans /3-carotene. It is clear, then, that selective absorption of carotenoids takes place into the intestinal mucosal cell. 

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