Lecithin is a complex mixture of phospholipids found mainly in egg yolks, soy, and cole seeds. Phospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and phosphatidyl glycerol compose the lipid bilayer of the cellular membrane structure. The energy needed for membrane biogenesis is stored in membrane lipids. The matrix of cellular membranes is formed by polar lipids, which consist of a hydrophobic and hydrophilic portion and segregate the internal and external environment. Furthermore, membrane lipids act as first and second messengers in signal transduction and molecular recognition pathways, implying the variability of their biological roles. The administration of fresh phospholipids to replace damaged cell membranes and restore the structure and function of the cellular membrane is called lipid replacement therapy (LRT). LRT has been demonstrated to reduce fatigue, and is expected to be effective for the treatment of degenerative diseases, metabolic syndrome, and cardiovascular diseases .
The Properties of Lecithin
Effect on memory, cognition, and Alzheimer’s disease
Age-related alterations in cellular metabolism and cumulative oxidative stress are two pathways that have been associated with age-related cognitive deficits. Many age-related neurochemical changes can be traced to structural and functional alterations in neuronal membranes. Memory loss and deficiencies in mental cognition have been linked to a decline in phospholipids, especially phosphatidylserine (PS), in neuronal membranes. Due to this, administering endogenously occurring phospholipids may be able to prevent or reverse age-related neurochemical deficits .
High amounts of the phospholipids PS and phosphatidic acid (PA) are found in the neuronal membrane and are essential to its functioning, acting as a biological detergent, and keeping fatty substances soluble and cell membranes flexible. PS was also discovered to increase brain glucose metabolism, stimulate neurotransmitter release, and reduce oxidative stress in the brain. Experiments with PS-supplemented rodents have shown an improvement in memory, learning capacity, and other cognitive parameters. A 12-week pilot study with 30 elderly volunteers suggested that soy lecithin-derived PS (100 mg three times daily) may improve cognitive performance in elderly with memory complaints .
Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by progressive memory loss, spatial disorientation, cognitive dysfunction, and behavioral changes. The apolipoprotein E (APOE) gene variant known as APOE4 is the main genetic risk factor for late-onset AD . Approximately 95% of the total pool of choline compounds in most tissues is made up of a family of 1,2-diacylglycerophospholipids called phosphatidylcholines (PC), which is a crucial component of cell membranes. It has a common zwitterionic structure, with hydrophobic chains that vary in length and degree of saturation, and its structural roles are mostly determined by chain length (because variations in chain length can impact the fluidity of cell membranes). Along with its structural roles, it is also found as components of lipoproteins, in particular, HDL. PC interacts with ApoE as part of the HDL group, and is implicated in cholesterol transport. This is of interest, as ApoE is unambiguously associated with AD, with the ApoEε4 allele being the most significant susceptibility genetic factor .
Effect on menopausal symptoms
The effect of soy lecithin on menopausal symptoms, such as fatigue, and other relevant health parameters in Japanese middle-aged women was examined in this randomized, double-blind, placebo-controlled trial. The findings demonstrated that high-dose (1200 mg/day) soy lecithin not only increases vigor, but also lowers the diastolic blood pressure and cardio-ankle vascular index (CAVI) in Japanese middle-aged women who complained of fatigue .
The inner mitochondrial membrane is the main source of reactive oxygen species (ROS), which are produced when the electron transport chain is decoupled from ATP synthesis.
Reactive oxygen species (ROS) are generated in the process of uncoupling the electron transport chain from ATP generation, with the inner mitochondrial membrane being the most important source of ROS. When mitochondrial membranes are damaged by ROS, energy production by the organelle is decreased, which could lead to fatigue, as well as aging and various diseases. The majority of earlier studies have employed oral lecithin supplements at doses of 1 to 3 g per day to show how it affects inflammatory diseases, hyperlipidemia, cardiovascular diseases, cognitive impairment, and fatiguing illnesses. Oral administration of phospholipids has been shown to be generally safe. Regarding the duration of the treatment, most of the previous studies investigating the effects of dietary LRT supplement on fatigue examined for 8 weeks, meanwhile some examined for 1 or 12 weeks .
Effect on liver
The active ingredients contained in soy lecithin play an important role in maintaining the integrity, fluidity, and functions of cell membranes. It was reported that under carbon tetrachloride modeling, phospholipids can prevent the weight of the liver from increasing, encourage hepatocyte regeneration, and progressively restore the fascicular and lobular structures of the liver. Additionally, there have been reports that adding lecithin to the diet could improve the pathological changes in the liver of laying hens, as well as the abnormal expression of apoA I and apoB100 genes in the liver. The incidence rate of fatty liver hemorrhage syndrome in laying hens ranges from 5 to 30 percent. When the liver is damaged, the permeability of the liver cell membrane increases, and a variety of enzymes in the liver cells are released into the blood, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Therefore, the activities of these enzymes in the blood would increase. The liver has a role in fat metabolism in poultry. So, Increasing the dietary fat can increase the metabolic burden on the liver resulting in liver damage .
Lecithin mostly consists of PC, which is also the most prevalent phospholipid in all mammalian cell membranes. The synthesis and stability of lipoproteins depend on phospholipids. Together with cholesterol, phospholipids (particularly PC) form a monolayer surrounding a neutral lipid core consisting of triacylglycerols (TAG) and cholesteryl esters. Besides the major lipids – TAG, phospholipids and (esterified) cholesterol – other lipids, such as diacylglycerol (DAG) and sphingolipids – are also present in low amounts on lipoproteins. Apolipoprotein (apo) apoB100 is necessary for the assembly of TAG-rich lipoproteins [i.e. very low density lipoproteins, VLDLs] in humans’ livers, whereas apoB48 is necessary for the formation of TAG-rich chylomicrons in the intestine. In addition to apoB, PC is required for assembly and secretion of VLDLs and chylomicrons. It has been estimated that PC comprises 60–80% of the phospholipids on the surface of apoB-containing lipoproteins. Therefore, it is not surprising that impaired TAG-rich lipoprotein secretion results from lower PC production .
The synthesis of very low density lipoproteins (VLDL) requires PC as an essential substrate. In the presence of PC deficiency, VLDL synthesis and excretion are compromised, with the possible accumulation of triglycerides in the hepatocytes due to the reduced excretion or oxidation of fatty acids. Ethanol has a similar effect when it reduces the synthesis of PC, causing alteration of methionine metabolism. Thus, some investigators have tested the hypothesis that lecithin (which contains choline) supplementation may attenuate the ethanol-mediated free radical-induced hepatotoxicity and steatosis .
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- Sheila C, Guilherme V, Rafael D, Sérgio Z, Paula G, Helio V, Effects of Lecithin and Vitamin E Supplementation on Liver Steatosis and Oxidative Stress Induced by Chronic Ethanol Consumption in Rats. Scandinavian Journal of Laboratory Animal Science. 2010 [cited 2022 August 26]; 37: 1-8. Available form: https://www.researchgate.net/publication/235005510_Effects_of_Lecithin_and_Vitamin_E_Supplementation_on_Liver_Steatosis_and_Oxidative_Stress_Induced_by_Chronic_Ethanol_Consumption_in_Rats