577
enzyme activation (Pressman et al. 2017). Heat/cooking, thermal and non–thermal
processing, and cooking methods can result in variation in the bioavailabilities of
nutrients present (Jordan 2014). Storage affects the content of polyphenols, in some
fruits, vegetables, wines, and olive oils and refrigeration decreases their content
(Gliszczynska-Swiglo and Tyrakowska 2003). Variability of intestinal factors like
enzyme activity, transit time, colonic microflora, efflux transporters, and transporters influence bioavailability in individuals and nutritional milieu (Jordan 2014).
Dietary Fiber Dietary fibers mainly exist in unrefined cereals, legumes, nuts,
fruits and vegetables. The effect of dietary fiber on nutrient bioavailability is linked
to their physical properties in the gastrointestinal tract like cation exchange capacity, bile acid binding, water–holding capacity, viscosity, and ability to act as a substrate for fermentative microorganisms (Gallaher and Schneeman 2001). In general,
dietary fiber alone does not have a major effect on the absorption of minerals (e.g.
calcium or magnesium) (Heaney and Weaver 1995) or trace elements (Rossander
et al. 1992; Sandström 1997), although α–cellulose may affect the utilization or
endogenous losses of copper (Turnlund et al. 1985).
Lipids and Fatty Acids Lipids after their absorption in the intestine are broken
down (metabolized) to fatty acids with varying length of carbon chain. Fatty acids
with shorter chain length have lower melting points and therefore stays in liquid
form (Mahan and Raymond 2016; Titchenal et al. 2018). Absorption of fats and fatty
acids is affected by the water–holding capacity of dietary fibers such as pectins,
psyllium, and various gums, which retain water within their matrix, forming highly
viscous solutions in the small intestine. These can in turn alter gastric emptying time
and slow down the rate of nutrient digestion and absorption (Gallaher and Schneeman
2001). Fats also increase the bioavailability of phytochemicals, like lycopene (in
tomatoes) and β–carotene (in carrots) thus promote health and well–being. As a
result, eating tomatoes with olive oil or salad dressing facilitates lycopene absorption (Gibney et al. 2009; Mahan and Raymond 2016; Titchenal et al. 2018).
Vitamins Bioavailability of vitamins in the body is largely affected by their chemical forms (Gibson 2007) that varies with age, sex, and physiological condition of an
individual. Their quantities within the body are mostly regulated by the type of
dietary intakes and eating habits. Vitamin absorption can be adversely affected by
intake of tea, coffee (caffeine), smoking, alcohol, dietary fibers (phytates) etc.
(Aslam et al. 2017). Sometimes increase or decrease of one vitamin also affects overall vitamin absorption. Some drugs like antibiotics, anti–inflammatory, histamine,
anti–seizures, etc. decrease vitamin B complex, vitamin D and C levels in the body
cells. Some diseases like ‘celiac disease’ and ‘lactose intolerance’ affect the digestive processes and decrease the vitamin absorption. Vitamin A activity in the diet is
derived from retinoids like retinol, retinyl esters, and provitamin A carotenoids like
β–carotene, α–carotene, and β–cryptoxanthin. Generally, the bioavailability of retinol is high (70–90%) but the dietary fat and intestinal infections can affect its absorption. The absorption of retinol gets reduced in individuals with diarrhea and intestinal
25 Bioavailability of Nutrients and Safety Measurements
enzyme activation (Pressman et al. 2017). Heat/cooking, thermal and non–thermal
processing, and cooking methods can result in variation in the bioavailabilities of
nutrients present (Jordan 2014). Storage affects the content of polyphenols, in some
fruits, vegetables, wines, and olive oils and refrigeration decreases their content
(Gliszczynska-Swiglo and Tyrakowska 2003). Variability of intestinal factors like
enzyme activity, transit time, colonic microflora, efflux transporters, and transporters influence bioavailability in individuals and nutritional milieu (Jordan 2014).
Dietary Fiber Dietary fibers mainly exist in unrefined cereals, legumes, nuts,
fruits and vegetables. The effect of dietary fiber on nutrient bioavailability is linked
to their physical properties in the gastrointestinal tract like cation exchange capacity, bile acid binding, water–holding capacity, viscosity, and ability to act as a substrate for fermentative microorganisms (Gallaher and Schneeman 2001). In general,
dietary fiber alone does not have a major effect on the absorption of minerals (e.g.
calcium or magnesium) (Heaney and Weaver 1995) or trace elements (Rossander
et al. 1992; Sandström 1997), although α–cellulose may affect the utilization or
endogenous losses of copper (Turnlund et al. 1985).
Lipids and Fatty Acids Lipids after their absorption in the intestine are broken
down (metabolized) to fatty acids with varying length of carbon chain. Fatty acids
with shorter chain length have lower melting points and therefore stays in liquid
form (Mahan and Raymond 2016; Titchenal et al. 2018). Absorption of fats and fatty
acids is affected by the water–holding capacity of dietary fibers such as pectins,
psyllium, and various gums, which retain water within their matrix, forming highly
viscous solutions in the small intestine. These can in turn alter gastric emptying time
and slow down the rate of nutrient digestion and absorption (Gallaher and Schneeman
2001). Fats also increase the bioavailability of phytochemicals, like lycopene (in
tomatoes) and β–carotene (in carrots) thus promote health and well–being. As a
result, eating tomatoes with olive oil or salad dressing facilitates lycopene absorption (Gibney et al. 2009; Mahan and Raymond 2016; Titchenal et al. 2018).
Vitamins Bioavailability of vitamins in the body is largely affected by their chemical forms (Gibson 2007) that varies with age, sex, and physiological condition of an
individual. Their quantities within the body are mostly regulated by the type of
dietary intakes and eating habits. Vitamin absorption can be adversely affected by
intake of tea, coffee (caffeine), smoking, alcohol, dietary fibers (phytates) etc.
(Aslam et al. 2017). Sometimes increase or decrease of one vitamin also affects overall vitamin absorption. Some drugs like antibiotics, anti–inflammatory, histamine,
anti–seizures, etc. decrease vitamin B complex, vitamin D and C levels in the body
cells. Some diseases like ‘celiac disease’ and ‘lactose intolerance’ affect the digestive processes and decrease the vitamin absorption. Vitamin A activity in the diet is
derived from retinoids like retinol, retinyl esters, and provitamin A carotenoids like
β–carotene, α–carotene, and β–cryptoxanthin. Generally, the bioavailability of retinol is high (70–90%) but the dietary fat and intestinal infections can affect its absorption. The absorption of retinol gets reduced in individuals with diarrhea and intestinal
25 Bioavailability of Nutrients and Safety Measurements