337
the small intestine. In order for picolinic acid to be synthesized, the presence of
vitamin B 6 is necessary. The zinc picolinate complex is transported through the cell
to the small intestine (intestinum) and then to the liver where it is stored. Vitamin B6
deficiency can, especially in the elderly, lead to reduced zinc resorption. Zinc as
well as iron can be bound to a single protein in mucosal cells. It is then transmitted
through the serous membrane of the mucosal cell in the serum and binds to albumin.
Copper may affect zinc resorption due to competition for serum albumin binding
sites. When foods are high in phosphate and calcium, zinc deficiency can be more
severe. Zinc is processed in the juice of the pancreas and to a lesser extent in the
bile. Therefore, the major route of zinc excretion is via the feces. Significant
amounts of zinc can also be lost through sweating, especially in the tropics. When
the proportion of zinc (as well as copper) increases, it binds to metallothionein in
the liver. Zinc is not stored well enough in the body, so reducing zinc intake through
food can lead to zinc deficiency in the body relatively quickly. The level of zinc in
the body can best be determined by measuring it in erythrocytes and leukocytes.
Studies from 1997 showed that zinc resorption doubles during lactation, which
enables better milk synthesis, but there is no data that this happens during pregnancy. Hormone therapy can often be the cause of poor zinc resorption. In estrogen
treatment in postmenopausal women, zinc resorption decreases by 35% after only
3 months of treatment.
Phosphorus enters the body through food and is resorbed in the small intestine.
Any excess phosphorus is excreted from the body through the kidneys. Regulation
of calcium and phosphorus in the blood is performed by parathyroid hormone
(PTH) and vitamin D. A slight decrease in blood calcium (e.g., in case of insufficient intake of calcium in the body) leads to parathyroid glands increasing the secretion of PTH. PTH stimulates the translation of vitamin D in the kidney into its active
form. Increased levels of calcium in the blood lead to increased intestinal resorption
of calcium and phosphorus. Stimulation of PTH leads to decreased urinary calcium
excretion and increased phosphorus excretion.
Iron is mainly found in food in ferrous form (Fe
3+
) and is tightly bound to organic
molecules. In the stomach, where the pH is lower than 4, Fe
3+
can dissociate and
react with low-molecular-weight compounds such as fructose, ascorbic acid, citric
acid, and amino acids to form complexes that allow Fe
3+
to remain soluble at neutral
pH such as in the small intestine. Iron does not leave the heme in the stomach but as
such passes into the small intestine.
In healthy people, only 5–10% of iron is absorbed from food. In childhood, the
absorption is greatest and decreases with age. In foods of animal origin, iron is present in the form of organic heme iron, while in plant foods it is found in the form of
inorganic nonheme iron. These two types of iron are resorbed into different pathways. 20–30% of heme iron can be absorbed from food, as opposed to 2–5% of
nonheme iron. If vitamin C is also taken in through food, then the percentage of
adopted nonheme iron increases to about 50%. Vitamin A and beta-carotene can
also increase the uptake of nonheme iron. Iron must be in ferro form in order to be
resorbed, and the hydrochloric acid found in the stomach translates the ferric form
of iron into ferro. Iron resorption is a slow process that takes 2–4 hours. If the level
11 Chemical Composition and Nutritional Properties of Functional Food
the small intestine. In order for picolinic acid to be synthesized, the presence of
vitamin B 6 is necessary. The zinc picolinate complex is transported through the cell
to the small intestine (intestinum) and then to the liver where it is stored. Vitamin B6
deficiency can, especially in the elderly, lead to reduced zinc resorption. Zinc as
well as iron can be bound to a single protein in mucosal cells. It is then transmitted
through the serous membrane of the mucosal cell in the serum and binds to albumin.
Copper may affect zinc resorption due to competition for serum albumin binding
sites. When foods are high in phosphate and calcium, zinc deficiency can be more
severe. Zinc is processed in the juice of the pancreas and to a lesser extent in the
bile. Therefore, the major route of zinc excretion is via the feces. Significant
amounts of zinc can also be lost through sweating, especially in the tropics. When
the proportion of zinc (as well as copper) increases, it binds to metallothionein in
the liver. Zinc is not stored well enough in the body, so reducing zinc intake through
food can lead to zinc deficiency in the body relatively quickly. The level of zinc in
the body can best be determined by measuring it in erythrocytes and leukocytes.
Studies from 1997 showed that zinc resorption doubles during lactation, which
enables better milk synthesis, but there is no data that this happens during pregnancy. Hormone therapy can often be the cause of poor zinc resorption. In estrogen
treatment in postmenopausal women, zinc resorption decreases by 35% after only
3 months of treatment.
Phosphorus enters the body through food and is resorbed in the small intestine.
Any excess phosphorus is excreted from the body through the kidneys. Regulation
of calcium and phosphorus in the blood is performed by parathyroid hormone
(PTH) and vitamin D. A slight decrease in blood calcium (e.g., in case of insufficient intake of calcium in the body) leads to parathyroid glands increasing the secretion of PTH. PTH stimulates the translation of vitamin D in the kidney into its active
form. Increased levels of calcium in the blood lead to increased intestinal resorption
of calcium and phosphorus. Stimulation of PTH leads to decreased urinary calcium
excretion and increased phosphorus excretion.
Iron is mainly found in food in ferrous form (Fe
3+
) and is tightly bound to organic
molecules. In the stomach, where the pH is lower than 4, Fe
3+
can dissociate and
react with low-molecular-weight compounds such as fructose, ascorbic acid, citric
acid, and amino acids to form complexes that allow Fe
3+
to remain soluble at neutral
pH such as in the small intestine. Iron does not leave the heme in the stomach but as
such passes into the small intestine.
In healthy people, only 5–10% of iron is absorbed from food. In childhood, the
absorption is greatest and decreases with age. In foods of animal origin, iron is present in the form of organic heme iron, while in plant foods it is found in the form of
inorganic nonheme iron. These two types of iron are resorbed into different pathways. 20–30% of heme iron can be absorbed from food, as opposed to 2–5% of
nonheme iron. If vitamin C is also taken in through food, then the percentage of
adopted nonheme iron increases to about 50%. Vitamin A and beta-carotene can
also increase the uptake of nonheme iron. Iron must be in ferro form in order to be
resorbed, and the hydrochloric acid found in the stomach translates the ferric form
of iron into ferro. Iron resorption is a slow process that takes 2–4 hours. If the level
11 Chemical Composition and Nutritional Properties of Functional Food