Monograph: |
LACITHIN
Lecithin: Β Β Dietary lecithin contributes to the body stores of choline--a necessary precursor to cell membrane phospholipids. Phospholipids have a strong affinity for both water-soluble and fat-soluble substances. This property makes them effective structural materials in the body. Large concentrations of phospholipids are found in combination with protein in cell membranes, where they facilitate the passage of fat in and out of cells, and in the blood, where they also function in the transport of fats (as part of lipoproteins). Phospholipids also appear to play a critical role in generating second messengers for cell membrane signal transduction. This process involves a cascade of reactions that translate an external cell stimulus such as a hormone or growth factor into a change in cell transport, metabolism, growth, function, or gene expression. Disruptions in phospholipid metabolism can interfere with this process.
A limited number of studies have reported a lecithin-mediated increase in the absorption and/or utilization of certain nutrients in animal models. Kimura et al demonstrated improved absorption in rats of a lecithin-dispersed form of vitamin E (d-alpha-tocopherol acetate) compared to nonlecithin-dispersed forms. Boccio et al demonstrated increased bioavailability and stability of iron (ferrous sulfate) from milk in a mouse model. Microencapsulating the iron in fluid milk with lecithin resulted in a 46% increase in iron bioavailability compared to regular fluid milk. Thus, microencapsulation prevented the interaction of iron with other ingredients in milk that may have inhibited its absorption. Igarashi et al demonstrated increased cell membrane affinity of the antioxidant superoxide dismutase when chemically attached to lecithin, compared to unmodified superoxide dismutase.
Dietary lecithin, also known as phosphatidylcholine, is a phospholipid. It is widely distributed in foods and is an approved food additive. Dietary lecithin serves as a contributor to the body' stores of choline--a necessary precursor to cell membrane phospholipids. Large concentrations of phospholipids are found in cell membranes, where they facilitate the passage of fat in and out of cells, and in the blood, where they also function in the transport of fats (as part of lipoproteins). Dietary lecithin has also been shown to enhance absorption and/or utilization of certain nutrients in animal studies, but clinical data are lacking.
ACTION & USES
Choline circulating in the blood after PC ingestion is taken up into all cells of the body. The brain has a unique way of ensuring that its nerve cells will receive adequate supplies of circulating choline.
A special protein molecule within the brain's capillaries traps the circulating choline, and then transports it across the blood-brain barrier, into the brain. Once in the brain, choline is incorporated into the brain's own PC, which is an essential and major part of neuronal membranes. Circulating choline transported into the brain has an additional very important function for a special group of nerve cells that make a biochemical, acetylcholine, which is released into synapses as a neurotransmitter. It provides the essential precursor used to synthesize acetylcholine. Moreover, when nerve cells are active, firing frequently and releasing large quantities of acetylcholine, their ability to make adequate amounts of the neurotransmitter requires that they receive adequate amounts of choline from the blood stream. In the absence of adequate choline, the ability of nerve cells to transmit messages to other cells across synapses is impaired and neuronal cell membranes can be depleted of PC causing cell damage. In contrast, when supplemental choline is provided, these messages can be amplified and membrane structure maintained.
ADVERSE REACTIONS
No major side effects have been reported in connection with consumption of large quantities of phosphatidylcholine or commercially available (less pure) lecithin.
Minor side effects may be seen such as increased salivation, nausea and upset stomach.
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