Alpha-GPC has been used over the past decade to enhance cognition and memory. The dietary supplementation of Alpha GPC has been studied as an alternative treatment in various age-related conditions, including dementia, and cerebrovascular and Alzheimer's disease. Its mechanism of action is by the potentiation of growth hormone from the hypothalamus. It is thought to be particularly useful for elderly individuals, as they exhibit lower secretions of growth hormone with age. It may also be beneficial for individuals who wish to increase muscle mass via increased secretion of growth hormone.
The active constituent of Alpha GPC is choline. Choline is a phospholipid that is involved in the production and integrity of all cell membranes. It is also a precursor to acetylcholine, one of the main parasympathetic neurotransmitters in the brain. Acetylcholine is involved in many essential functions of the body, including memory, cognitive function, digestion, and respiratory and cardiovascular functions. Choline is also a methyl donor and is also used by the body to decrease elevated levels of homocysteine. This function may lend it the title of “antioxidant,” as homocysteine is correlated to an increase in damage from free radicals and oxidative stressors.
Alpha-GPC is considered a non-essential nutrient. It is usually taken as a supplement, serving as a delivery platform for choline, a phospholipid that is now considered to be essential. Alpha-GPC is derived from soy lecithin. It is not a phospholipid itself, but is derived from one. The most bioavailable form of choline known, Alpha GPC, is 40% choline.
The source currently being utilized in supplements for Alpha GPC is soy lecithin. Other foods that contain Alpha GPC include liver, eggs, and milk. Unprocessed cows milk is believed to contain 250 mg of Alpha GPC per liter. Alpha GPC is therapeutically beneficial, due to the high amounts of choline it contains. It is believed to have the highest bioavailability of choline, at 40%. It is digested in the small intestine where choline is readily absorbed.
Choline, the main constituent of Alpha GPC, can also be found in other vegetable and animal sources. The following chart contains the amounts of choline found in common foods:
|Food source (100 g)||Amount of Choline (mg)|
Figure 1: Choline Content of Various Food Sources 
Alpha-GPC is typically used as a cognitive enhancement supplement. It has shown potential benefit in age-related conditions, such as dementia, Alzheimer’s, and cerebrovascular dementia. It is also considered as an effective agent for memory enhancements. The majority of physiological effects by Alpha GPC can be attributed to an increase in acetylcholine production via delivery of choline, a precursor molecule of acetylcholine.
Alpha GPC has been extensively studied as a therapy for Alzheimer’s disease. A deficiency of acetylcholine is one proposed mechanism for the development and progression of this disease. A “loading” of precursors to acetylcholine may be effective at improving cognition in those suffering from mild to moderate Alzheimer’s disease. 
Alpha GPC is also effective at treating dementia related to cerebrovascular accidents, like stroke and TIAs (transient ischemic attacks).  In clinical study, the supplementation of Alpha GPC was able to restore cognitive function after an initial loss caused by oxygen deficiency. Cognitive recovery was measured via the MiniMental State Test, Matthew Scale, Crichton Rating Scale, and the Global Deterioration Scale. Alpha-GPC has been shown to be superior to both choline and lecithin, for the treatment of dementia due to cerebrovascular accidents. 
Alpha GPC is also effective for age related dementia. It is believed to have parasympathomemetic activity, improving mental clarity and memory.  Alpha GPC has proven superior to, or effective as, drug therapy in a multitude of studies.
Alpha GPC may also be used to increase levels of growth hormone. Growth hormone naturally declines with age. Alpha GPC may be useful in providing a reduction in the declination of growth hormone as we age. Although not substantiated, Alpha GPC could possibly be used to enhance or increase the production of growth hormone for the purpose of building muscle.
Supplementation with Alpha-GPC results in an increased response of growth hormone secretion to growth hormone releasing hormone.  Results were significant in both the elderly, who had lower levels of growth hormone, and the young, who had normal physiologic levels of growth hormone. It is important to note that the action of Alpha GPC was not on the secretion of growth hormone directly, but indirectly via an increase in the response to growth hormone releasing hormones (i.e. Somatostatin).
The recommended therapeutic dose of Alpha-GPC is 500 - 1,000 mg per day. Most studies testing the efficacy of Alpha GPC as a therapy for cognitive function or growth hormone stimulation use a standard dose of 400 mg, taken three times daily. There are no established dosages or recommended intakes of Alpha GPC.
The following table lists the Dietary Reference Intakes for choline across various age groups. Because Alpha GPC is 40% choline, the recommended intakes for choline are listed below. The established upper limit for choline is set at 3,500 mg per day.
|Age group||Age||Adequate Intake (mg)|
|Infants||0-5 months||125 or 8 mg/kg|
|6-11 months||150 or 17 mg/kg|
Figure 2: DRI for Choline
Since Alpha GPC is not an essential nutrient, there are no known deficiencies. However, a deficiency in choline can result in liver disease.  Because choline is found so readily in various food sources, deficiencies are uncommon. Certain populations are at increased risk for deficiencies, including critically ill patients, and patients on total parenteral nutrition (TPN).
A serious condition caused by a deficiency in choline that can develop in patients on TPN is fatty liver.  Fatty liver is the result of improper lipid metabolism in the liver. This occurs with a deficiency of choline because of its role in phospholipid and cholesterol metabolism. Choline is required for synthesis of VLDL, a cholesterol molecule that is involved in the synthesis of bile. Fatty liver due to choline deficiency can be completely reversed with supplementation of choline (IV).
A deficiency of choline may also be related to the development of certain types of cancer.  In malignancies, choline deficiency results by means of the build up of enzyme 1,2 diacylglycerol, which activates the signaling molecule, protein kinase C. Abnormal levels of protein kinase C may trigger cancer development.
Side effects of Alpha GPC supplementation can include; heartburn, nausea, vomiting, insomnia, headache, rash, and diarrhea. The risk of side effects has been shown to be less than 1.8%.  An overdose of Alpha GPC can cause hypotension.  It is important to note that discontinuing treatment/supplementation can reverse every adverse effect or toxicity.
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