L-Glutamine is the most abundant amino acid in the bloodstream and in the body. It is involved in more metabolic processes than any other amino acid, fulfilling a number of biochemical needs. It operates as a nitrogen shuttle, taking up excess ammonia and forming urea. Ammonia, a by-product of certain normal biochemical reactions in the body (including the brain) is toxic to the human body and thus glutamine serves an important function in helping to convert ammonia into urea, a non toxic end product, which the body can easily eliminate. L-Glutamine can contribute to the production of other amino acids, glucose, nucleotides, protein and glutathione. It is the principal metabolic fuel for the epithelial cells that line the small intestine (enterocytes), and for certain immune cells, namely lymphocytes, macrophages, and fibroblasts.1
Grape Seed Extract and pine bark extract belong to a group of compounds known as procyanidolic oligomers (PCO). These extracts contain flavonoids called proanthocyanidins, which are bound to other proanthocyanidins forming proanthocyanidin dimers, trimers, tetramers and larger molecules. These unique flavonoid compounds are powerful antioxidants and have been shown to inhibit the destruction of collagen, preserving the integrity of blood vessels and capillaries throughout the body. These features make them useful agents in the prevention and treatment of capillary fragility, venous insufficiency, varicose veins, diabetic retinopathy and macular degeneration. They also inhibit the inflammatory process to a certain degree. 1,2
Grape Seed Extract and pine bark extract (Pycnogenol) products should contain 92-95 percent and 80-85 percent PCO, respectively, to ensure sufficient amounts these bioactive agents
Supplementation Studies and Clinical Applications
1. Blood Vessel Support
PCO support collagen and ground substance, decreasing capillary permeability and fragility. PCO extracts have been used to treat venous and capillary disorders, including venous insufficiency, varicose veins, capillary fragility, diabetic retinopathy and macular degeneration of the eye.3-9
2. Connective Tissue Support
PCO support the collagen and ground substance of tendons, ligaments and cartilage. They also help to prevent cartilage destruction associated with inflammation and arthritis. PCO also inhibit the release of pro-inflammatory mediators such as histamine, proteases, prostaglandins and leukotrienes. PCO also demonstrate powerful antioxidant function. No clinical trials with arthritis patients have been published, however, anecdotal evidence and biological plausibility suggest that PCO extract supplementation may be useful in chronic arthritic and connective tissue disorders.10,11,12
PCO extract has been used to help reverse or stabilize diabetic retinopathy and macular degeneration. It has also been used to improve visual performance in the dark and after exposure to glare (200 mg per day).
Daily Dosage (standardized to 92-95% PCO content)
1. Therapeutic Purposes (Venous insufficiency, varicose veins, capillary fragility, diabetic retinopathy, macular degeneration): 150-300 mg per day, in divided doses
2. General Health Support: 50-75 mg per day2
Toxicity and Contraindications
Procyanidolic oligomer extracts have been shown to be very non-toxic. They are water-soluble and any excess is excreted in the urine. No side effects have been reported to date.
There are no known drug interactions for procyanidolic oligomer extracts.
1. Schwitters B, Masquelier J. OPC in Practice: Biflavanols and their Applications. Rome, Italy: Alfa, Omega; 1993.
2. Murray M. The Healing Power of Herbs. 2nd edition. Rocklin, CA: Prima Publishing; 1995. p. 184-91.
3. Henriet JP. Veno-lymphatic insufficiency. Phlebologie 1993;46:313-25.
4. Lagrue G, Oliver-Martin F, Grillot A. A study of the effects of procyanidolic oligomers on capillary resistance in hypertension and in certain nephropathies. Sem Hosp Paris 1981;57:1399-401.
5. Gomez Trillo JT. Varicose veins of the lower extremities:symptomatic treatment with a new vasculotrophic agent. Prensa Med Mex, 1973;38:293-6.
6. Soyeux A, et al. Endotelon: Diabetic retinopathy and hemorrheology (preliminary study). Bull Soc Ophthalmol Fr 1987;87:14441-4
7. Proto F, et al. Electrophysical study of vitis vinifera procyanoside oligomers effects on retinal function in myopic subjects. Ann OH Clin Ocul 1988;114:85-93.
8. Corbe C, Boissin JP, Siou A. Light vision and chorioretinal circulation: study of the effect of procyanidolic oligomers (Endotelon). J Fr Ophthalmol 1988;11:453-60.
9. Boissin JP, Corbe C, Siou A. Chorioretinal circulation and dazzling: use of procyanidol oligomers. Bull Soc Ophthalmol Fr 1988;88:173-4,177-9.
10. Masquelier J, Dumon MC, Dumas J. Stabilization of collagen by procyanidolic oligomers. Acta Therap 1981;7:101-5.
11. Tixier JM, Godeau G, Robert AM, Hornebeck W. Evidence by in vivo and in vitro studies that binding to pycnogenols to elastin affects its rate of degradation by elastases. Biochem Pharmocol 1984;33(24):3933-9.
12. Maffei F, Facino R, Carinin M, et al. Free radicals scavenging action and anti-enzyme activities of procyanidines from Vitis vinefera. Arzniem Forsch 1994;44:592-601.
13. Murray M. Encyclopedia of Nutritional Supplements. Rocklin, CA: Prima Publishing; 1996. p. 320-31.