Carnosine is a protein made of just two amino acids, alanine and histidine. Because this tiny protein is made of just two amino acids, it is always formed perfectly and acts predictably in various physiological processes. Carnosine is most abundant in the skeletal muscles (the muscles we use for movement), the heart, and the brain.
What Is L-Carnosine?
The “L” in L-carnosine refers to the direction in which crystalline carnosine reflects polarized light. The carnosine molecule is made from the combination of L-histidine and alanine and also exists in an “L” form.
L-carnosine, more specifically zinc-L-carnosine, is the form of carnosine used in nutritional supplements. If you were to look up zinc-L-carnosine in the medical literature, you would find it under another name, polaprezinc.
The zinc in L-carnosine is a chelate, which means it does not form a new chemical compound with L-carnosine. Instead, it is “captured” by L-carnosine. Groups of L-carnosine molecules can also trap nickel, copper, cadmium, manganese, copper, calcium, strontium, and beryllium, but L-carnosine is not typically combined with these metals and it has not been tried as chelation therapy for them.
L-carnosine is not the only form of carnosine used in nutritional supplements. N-acetyl-carnosine is a form of carnosine made by the reaction of carnosine with acetic acid. This form of carnosine does not capture heavy metals, but it also is not broken down by an enzyme called carnosinase, which can turn carnosine back into its constituent amino acids, alanine and L-histidine. N-acetyl-carnosine is the form of carnosine used in experiments for treating eye diseases.
Both forms of carnosine are thought to fight glycation, which can be described as “caramelization” of proteins in the bloodstream and in nerve tissue by excessive levels of sugar. When proteins join with glucose, they cease to function, and they release free radicals that can spread tissue damage even further. The N-acetyl form of carnosine is most commonly used to treat conditions cause by diabetes and chronically high blood sugar levels.
L-Carnosine for Fighting Stomach Ulcers
Zinc-L-carnosine supplements are often offered as nutritional support for people who have gastric or duodenal ulcers, that is, ulcers in the stomach or small intestine. Researchers in Japan have found that this form of carnosine induces the formation of an enzyme called heme oxygenase. The way this enzyme works is literally to keep the iron released from bleeding lesions in the lining of the digestive tract from “rusting” the healthy tissues of the stomach. It helps transform free iron released by damaged red blood cells into ferritin, which is much less inflammatory and destructive.
Zinc-L-carnosine has been used successfully to stop stomach irritation caused by histamine (that is, triggered by allergies to food or medication), aspirin, acetaminophen (Tylenol), stress, and poor circulation, also known as ischemia. In the digestive tract, ischemia is typically an undetected problem. Especially in type 2 diabetics, the linings of the arteries that provide oxygen to the stomach and bowel can stop generating enough of the compound that keeps them open. Even without high cholesterol, the artery gets narrower and narrower and provides less and less blood to the digestive tract.
At some point, some other event (in one case, I know very well, drinking ice water after getting hot and thirsty) can close off circulation entirely, and the linings of the stomach and bowel become inflamed and start to die. Zinc-L-carnosine can help stop this process if the inflammation is not so severe that food and drink cannot be taken by mouth.
In treating ischemia, the benefits of L-carnosine can be dramatic. In treating ulcers, the benefits of L-carnosine are primarily preventing flare-ups after eating the “wrong” food or taking an irritating medication.
Anti-Aging Benefits of Carnosine
Carnosine is also recommended for slowing the progression of cataracts and Alzheimer’s disease. Let’s consider the benefits of carnosine for cataracts first.
Russian scientists formulated eye drops containing the N-acetyl form of carnosine as a treatment for cataracts. Innovative Vision Products in Newcastle, Delaware, in the USA, developed an extended-release form of N-acetyl-carnosine eye drops that they claim can deter cataracts, diabetic retinopathy, wide-angle and closed-angle glaucoma, and macular degeneration.
Those are bold and far-reaching claims. Are they true? Are they, at best, premature?
Veterinarians at Cambridge University in the UK have found that N-acetyl carnosine eye drops can partially reverse cataracts in older dogs. A series of studies published in Russian in 2007, 2008, and 2009, found that N-acetyl-carnosine eye drops can improve the results of Excimer laser treatment of cataracts experimentally induced in lab rats. An enthusiastic report published in the American Journal of Therapy in 2009 reported that “in a cohort in excess of 50,500 various patients seeking cutting-edge medical care,” N-acetyl-carnosine was “judged to have sufficient” efficacy.
Personally, I am more comfortable with research results that allow the reader to make his or her own judgments about whether the efficacy of a treatment is “sufficient.” The Royal College of Ophthalmologists in the UK, which supported the experiments in reversing cataracts in aged canines, put out a statement saying:
“The evidence for the effectiveness of N-acetyl carnosine eye drops is based on experience on a small number of cases carried out by a Russian research team. To date, the research has not been corroborated, and the results replicated by others. The long-term effect is unknown. Unfortunately, the evidence to date does not support the ‘promising potential’ of this drug in cataract reversal. More robust data from well-conducted clinical trials on adequate sample sizes will be required to support these claims of efficacy. Furthermore, we do not feel the evidence base for the safety is in any way sufficient to recommend its use in the short term. More research is needed.“
I have to agree. There is no reason to believe that an N-acetyl carnosine supplement taken by mouth would cause any harm. There is reason to hope that an N-acetyl carnosine eye drop solution might “dissolve” cataracts and even help other eye diseases, but the proof just is not available yet. Don’t forgo another treatment or stop a medication hoping that you can just use carnosine for your eyes.
I have searched for anecdotal information regarding the use of the Brite Eyes and Can-C N-acetyl-carnosine drops, and what I have found is that people who already have cataracts say that it helps with glare, although it does not stop the progression of the disease. There are testimonials that these products have cured glaucoma-but the proof would always be your eye pressure readings taken at the doctor’s office. There are also testimonials of relief from dry eyes that precluded continued use of contacts.
If you start taking these drops, you should allow six to nine months for any improvement at all. If you neglect some other treatment that works for that long, you could do your eyes some serious damage. Don’t take N-acetyl-carnosine eye drops unless you are also taking all other available treatments for your condition.
Carnosine for Cardiovascular Conditions
There has been a small body of research, most of it published in Russian scientific journals, that has found that carnosine relaxes blood vessels while improving the ability of the heart muscle to pump blood. Researchers don’t know whether carnosine works inside the cell, outside the cell, or in the plasma of the bloodstream. They just believe it works, at least on the basis of experiments conducted with laboratory animals. Like carnosine for cataracts, carnosine for cardiovascular conditions is promising, but a recommendation to use it would be premature.
Carnosine for Diabetics
There have been experiments with animals that have found that L-carnosine accelerates wound healing. In theory, it should be helpful for hard-to-heal wounds aggravated by diabetes, but there is no good data on how much to take.
What About Carnosine for Alzheimer’s?
One of the best-known advocates of carnosine for Alzheimer’s care is a British researcher named Alan R. Hipkiss. Dr. Hipkiss is a senior fellow at the University of Birmingham.
Hipkiss points out that researchers have been looking for a nutritional supplement for Alzheimer’s that:
- Captures heavy metals,
- Reverses glycation, the process of “sugar coating” nerve cells, and
- Fights inflammation.
Dr. Hipkiss points out that carnosine fits the bill. Also, certain drugs that stop seizures are known to raise levels of carnosine in the brain, and carnosine can be formulated as a nose spray that is absorbed more quickly into the brain. Scientists at Hamilton Health Sciences have found that the enzyme carnosinase becomes less active the longer people have Alzheimer’s and other forms of dementia, which may suggest that carnosine is depleted in the brain in these conditions. (There are other explanations for this observation.) But do we know that carnosine will relieve the symptoms of Alzheimer’s?
Unfortunately, the proof just isn’t there yet. Because it is very difficult to keep Alzheimer’s patients on a routine, and there are many other supplements that are better known to be helpful in Alzheimer’s, I wouldn’t even experiment with carnosine for Alzheimer’s at this time.
Carnosine for Autism
It is also difficult to keep children with autism on a supplementation schedule. For autism, however, supplementation with L-carnosine is worth a try.
Researchers at Autism and Epilepsy Specialty Services in Lake Bluff, Illinois, in the USA, gave 31 children with autistic spectrum disorder 800 mg of L-carnosine daily for 8 weeks and then assessed the children with a battery of psychological tests. The children did not do significantly better on the Childhood Autism Rating Scale (CARS). This is a test designed to rate:
- activity level
- adaptation to change
- body use
- emotional response
- fear and nervousness
- imitation
- level and consistency of intellectual response
- listening response
- non-verbal communication
- object use
- relationship to people
- taste-smell-touch response and use
- verbal communication
- visual response
- general impressions
However, the children did do better when assessed with the Gilliam Asperger’s Disorder Scale. This measurement index has more scales than the CARS and may capture smaller changes. By this measurement, children improved overall, and on the Behavioral, Communication, and Socialization subscales.
Dr. Michael Chez of the Autism and Epilepsy Services Center reports that he has now put about 1,000 autistic children on L-carnosine with about a 90% success rate. Sometimes the results are dramatic, but since most autistic children receive multiple medications, multiple therapies, and multiple nutritional supplements, it is hard to tell how well any individual child will do after starting L-carnosine. The complete recommendation of the Autism and Epilepsy Services Center is:
- 400 mg of L-carnosine, twice a day,
- 50 IU of vitamin E (as alpha-tocopherol, although mixed tocopherols and tocotrienols would also be acceptable) twice a day, and
- 5 mg of zinc twice a day. Any form of zinc is acceptable.
Many parents ask whether a smaller child might need less of these supplements, or a larger child might need more. My suggestion is that these amounts are OK for any child over the age of three, and simply see if these dosages work. And please share your experiences in the Comments Box.
What Is the Normal L-Carnosine Dosage?
For children, the normal dosage of L-carnosine taken by mouth is 400 mg twice a day. Adults may take up to 1,000 mg twice a day. If you are taking L-carnosine for ulcers, take the supplement on an empty stomach with a glass of warm water.
N-acetyl-carnosine is used in eye drops. If you choose to use the eye drops, take them as recommended by the manufacturer.
Are There Any L-Carnosine Side Effects?
If you were to be injected with about 1% of your body weight in L-carnosine, you would experience toxic effects. This is approximately 500 to 2000 times the recommended dosage, and you would not be able to absorb that much L-carnosine through your digestive system. L-carnosine has essentially no toxicity and no side effects when used as a dietary supplement.
Selected References:
Arakawa T, Satoh H, Nakamura A, et al. Effects of zinc L-carnosine on gastric mucosal and cell damage caused by ethanol in rats. Correlation with endogenous prostaglandin E2. Dig Dis Sci 1990;35:559-66.
Bonfanti L, Peretto P, De Marchis S, Fasolo A. Carnosine-related dipeptides in the mammalian brain. Prog Neurobiol 1999;59:333-53.
Cho CH, Ogle CW. A correlative study of the antiulcer effects of zinc sulfate in stressed rats. Eur J Pharmacol 1978;48:97-105.
Frommer DJ. The healing of gastric ulcers by zinc sulfate. Med J Aust 1975;2:793-6.
Kashimura H, Suzuki K, Hassan M, et al. Polaprezinc, a mucosal protective agent, in combination with lansoprazole, amoxicillin, and clarithromycin, increases the cure rate of Helicobacter pylori infection. Aliment Pharmacol Ther 1999;13(4):483-7.
Nishiwaki H, Kato S, Sugamoto S, et al. Ulcerogenic and healing impairing actions of monochloramine in rat stomachs: effects of zinc L-carnosine, polaprezinc. J Physiol Pharmacol1 999;50:183-95.
Quinn PJ, Boldyrev AA, Formazuyk VE. Carnosine: its properties, functions, and potential therapeutic applications. Mol Aspects Med 1992;13:379-444.
Roberts PR, Black KW, Santamauro JT, Zaloga GP. Dietary peptides improve wound healing following surgery. Nutrition 1998;14;266-9.