Another source for cystein : the Whey ! and it is natural. Pls see following link which I partially quote. It claims it gets through BBB ...
FEEDBACK GREATLY APPRECIATED

http://64.233.169.104/search?q=cache...lnk&cd=5&gl=jo
"WHEY PROTEIN & GLUTATHIONE Whey Protein contains essential amino acids which are noted to provide overall health benefits. More specifically, whey protein is very beneficial because whey protein drinks increase Glutathione (GSH) concentration in a number of tissues. Whey-based peptide studies have shown that whey protein may reduce hypertension which contributes to cardiovascular diseases. In fact, one of whey protein’s major benefits is to assist in the building of collagen. Therefore, by supplementing whey protein to your diet, it helps to accelerate the healing of fractures as well as provide overall health benefits. Whey protein is also helpful in the prevention and treatment of Osteoporosis. American Journal of Clinical Nutrition, June 2000.Whey protein increases Glutathione levels. Glutathione (GSH) is a powerful antioxidant. It is a tripeptide protein (made within the body) from three key amino acids; Cysteine, Glutamic Acid, and Glycine. The benefits of Glutathione include detoxifying many toxic chemicals and heavy metals from the body such as lead, mercury, aluminum, arsenic and cadmium, as well as the effects of alcohol and tobacco smoke. In the Immune System, Glutathione inhibits the excessive production of Cytokines that are implicated in Autoimmune Disease. Glutathione combats Free Radicals that cause allergies and aids in Chronic Fatigue. In regards to aging and life extension, old cells contain 20% less Glutathione compared to young cells, indicating it may be beneficial. In the Cardiovascular System, Atherosclerosis patients generally exhibit reduced Glutathione, indicating it may be beneficial. Brink; Life Ext., 6(2), 2000"
--
"THE EFFECTS OF WHEY PROTEIN ON NEUROTRANSMITTER FUNCTION Essential Amino Acids, the building blocks that make up proteins, play a large part in every living cell in the body. Each group of amino acids is tailored for a specific need. It is actually the amino acids rather than the proteins that are the essential nutrients. Amino acids act as neurotransmitters to carry information from one nerve cell to another. The neurotransmitter dysfunction is caused by the lack of amino acids. The dysfunction of the neurotransmitters results in depression and obesity with further results in diabetes, heart diseases, hypertension (high blood pressure), and lack of emotional control. “Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults,” Elena Volpi, Hisamine Kobayaski, Melinda Sheffield-Moore, Bettina Mittendorfer, and Robert R. Wolfe, Am J Clin Nutr 2003;78:250-8. Amino acids also act as neurotransmitters to carry information from one nerve cell to another. Amino acids enable vitamins and minerals to do their jobs properly, but if there is a deficiency in amino acids, nerve cells can’t function. There are approximately 28 amino acids. The liver produces 19 amino acids while the other 9 must be obtained from the diet which is called the essential amino acids. Prescription for Nutritional Healing, James F. Balch, M.D., Phyllis A. Balch, CNC, 1997, Page 34-35.Plainly, the neurotransmitter dysfunction is caused by the lack of amino acids. The dysfunction of the neurotransmitters results in depression and obesity with further results in diabetes, heart diseases, hypertension (high blood pressure), and lack of emotional control. The neurotransmitters are fat soluble and cannot cross the blood/brain barrier. Therefore, the amino acids that made up the neurotransmitters must cross the blood/brain barrier and then the body makes the neurotransmitters out of the amino acids and the appropriate vitamins and minerals necessary. Neurotransmitter Testing and Amino AcidTherapy, Marty Hinz, MD, NeuroResearch, Morgan Park Clinic, Duluth, Minnesota, 2002, Pages 22-24.Nutritional deficiency is a major cause of neurotransmitter dysfunction, as well as drugs such as Zoloft and Prozac. These drugs inhibit the reuptake of serotonin and so cause a loss of serotonin. Neurotoxic effects are permanent. They are caused by heavy metals, chemicals and drugs. The main drug that causes neurotoxicity is amphetamines. Neurotoxic effects are in the post-synaptic neurons. The treatment is the same as deficiency of amino acids, but it takes more of these amino acids forming serotonin to be effective at the post-sympathic neuron. Neurotransmitter Testing and Amino Acid Therapy, Marty Hinz, MD, NeuroResearch, Morgan Park Clinic, Duluth, Minnesota, 2002, Pages 22-24"