L-Cysteine – N-Acetyl-L-Cysteine Amino Acid Benefits & Health Foods?


Also known as N-acetyl-L-cysteine (NAC), L-Cysteine is a supplement that is used to improve the overall health of human beings, and is used both for nutritional as well therapeutic purposes.

The basic unit of glutathione, L-Cysteine helps in increasing the body's glutathione levels, which are essential for many bodily functions, including but not limited to your brain and lungs, as well as for liver detoxification. Needless to say, your brain and body tissues need as much  L-Cysteine as they can absorb, considering that the human body is very prone to depletion of glutathione levels, especially if you suffer from certain medical conditions.

Furthermore, L-cysteine can also break-up mucus, which makes it much easier to expel phlegm from the body (by coughing it up) that often forms due to pulmonary and respiratory conditions. L-cysteine is also required to regulate glutamate levels, which in turn influence the neurons present in your body's central nervous system.

L-cysteine is extensively required by your body to fight the oxidative stress which affects the lungs and the brain.  While the human body does make L-cysteine in small amounts, you can purchase L-cysteine supplements and high-protein foods.

What Is L-Cysteine?

L-cysteine is created by the body in small quantities, thus the reason it has been classified as an amino acid of the “semi essential” category. However, there are many people who can – and do – benefit from L-cysteine by consuming more of it in the form of supplements or as a part of their diets.

While the body can manufacture L-cysteine with the help of the amino acids methionine and serine, there are some other elements that are required as well, such as vitamin B6, vitamin B12 and folate in order to sufficiently produce it.

In addition to making the amino acids glycine and glutamine, your body requires L-cysteine to produce glutathione also known as the “king of all antioxidant” which is critical to your health. Important as it is, L-cysteine is often found in lesser quantities. You must, therefore, make sure that you have enough of it, even if it is not considered essential.

While L-cysteine has other benefits, such as breaking mucus, and killing oxidative stress, it is most essential to make glutathione; according to many longevity researchers, glutathione's importance in your body goes to the extent that its level in your cells might just determine your lifespan. Given that it lies within the cell, and is responsible for combating cell damage and maintaining a stable immune system., this makes it your body’s most essential antioxidant.

The Benefits Of L-Cysteine

Acts As A Powerful Antioxidant

By destroying the free radicals which lead to cellular damage through oxidative stress, L-Cysteine improves your body's capacity to store antioxidants by preserving glutathione. This most well-known benefit of L-cysteine is said to have many extra benefits such as slowing down aging and treating and/or preventing several serious health conditions.

Furthermore, by accomplishing all of this, L-cysteine also supports the immune system's functioning. According to research, many of the functions of the body's immune system that are related to diseases caused by deficiency of glutathione and cysteine, can be enhanced or even restored with the help of L-cysteine supplements.

Studies conducted on HIV patients have revealed that L-cysteine helps boost the immune system: a formula that included NAC, omega-3 fatty acids, bovine colostrum and several different minerals and vitamins worked together to slow down the accelerated loss of immune cells; by replenishing glutathione, L-cysteine had a positive impact on the functioning of the immunity of HIV patients.

L-cysteine supplements also improve immune function among women in their post-menopause period, according to study that was published in the medical journal Free-Radical-Biology-and-Medicine in 2008.

This study reports that regular dosage of NAC over a short period (2-4 months) might lead to an increased immune functioning among post-menopausal women. In fact, by decreasing the probability of many immune system diseases, such as infections, L-Cysteine helps post-menopausal women lead a better quality of life.

Promotes Detoxification

Due to its anti-oxidant properties, L-cysteine works to prevent several side effects that are caused by toxic chemicals as well as drugs. According to a study published in the Alternative Medicine Review, L-cysteine plays an essential role in the body's detoxification process which reverses damage done to the body's glutathione levels caused by pro-oxidative effects of toxic chemicals.

It is because of this property of L-cysteine, doctors often prescribe intravenous NAC to individuals going through acetaminophen overdose – to reduce or if possible, prevent kidney and liver damage by increasing glutathione-activity in the body.

Increases Male Fertility

Since L-cysteine helps combat oxidative stress by alleviating glutathione depletion, it additionally acts as a rather effective treatment of infertility – especially among men with poor-quality semen, oxidative stress, and DNA damage.

According to a clinical study conducted in 2016, NAC can act as an efficient treatment for infertility in men caused by clinical varicocele (a condition when veins inside the scrotum get enlarged). According to the study's results, NAC was shown to improve sperm concentration. Furthermore, it was also observed to improve the odds of getting and staying pregnant.

Stabilizes Blood Sugar Levels

L-cysteine assists in supporting the body’s natural capacity to regulate and stabilize its own blood sugar levels. According to data generated by a study on animals that was conducted in 2009, L-cysteine supplements helped in reducing vascular inflammation-markers and lowering glycemia among patients suffering from diabetes. Furthermore, rats that were treated with L-cysteine were observed to have significantly-lowered glucose-levels, plasma-protein-oxidation levels as well as insulin resistance.

Supports Digestive Health

Due to its anti-aging properties, L-cysteine helps improve your body's digestive capacity. As people age, many digestive issues such gastroenteritis and low-stomach-acid become prominent. This generally happens due an increase in the number of free-radicals in your body.

L-cysteine supplements can also help reduce symptoms of other digestive issues such as ulcerative colitis (this is an inflammatory-bowel disease which causes sores as well as long-lasting inflammation inside the digestive tract). Furthermore, many researchers have found a combined therapy comprising mesalamine and NAC, which helps improve ulcerative colitis symptoms by decreasing chemokine-levels, which in turn produce free radicals and attract WBCs.

Relieves Symptoms Of Respiratory Conditions

Given that NAC can break down your body's mucus content, it can act as a great expectorant. By boosting the body's glutathione levels and thinning-up the mucus that tends to build-up inside bronchial tubes, NAC helps decrease the frequency and severity of respiratory and wheezing attacks. This is especially helpful to those people who suffer from allergies or from respiratory conditions such as COPD or bronchitis.

According to scientific research, L-cysteine supplements can also be used to bring down inflammation and oxidant burden present in patients suffering from COPD – a respiratory condition that is characterized by restricted airflow and an abnormal level of inflammation in the lungs. So far, NAC has indeed been used by many patients to control COPD symptoms and the accelerated loss of lung-function.

Helps In Treating Psychiatric Disorders

Using NAC to treat psychiatric illnesses is an increasingly promising prospect; according to a review published in the popular medical journal, Journal-of-Psychiatry & Neuroscience, many disorders which have otherwise very limited options for treatment can benefit greatly from NAC treatments.

Furthermore, research has also revealed NAC to be a potential treatment for many other conditions, such as addiction, which includes nicotine addiction, marijuana dependence, cocaine addiction as well as pathological gambling.

According to a recent case report, NAC can also be used to treat psychological disorders such as OCD by improving the patients’ habit of washing compulsively as well as treating their obsessional triggers.

NAC also has the potential to treat brain disorders such as schizophrenia, since its antioxidant activity plays a major role combating oxidative stress and stabilizing glutamate levels – the lack of which are often the reason of brain disorders.

While glutamate is indeed essential for the brain to function normally, it can cause brain damage if present in excess amounts. L-cysteine can help stabilize these levels, and in turn treat or even prevent brain disorders such as schizophrenia.

Additionally, many preliminary studies have revealed that L-cysteine can also help in treating and preventing the following conditions:

  • angina (characterized by the heart getting restricted blood flow)
  • acne
  • asthma
  • lung and colon cancer
  • emphysema

L-Cysteine Foods And Recipes

Believe it or not, L-Cysteine is not all that rare. Many foods that are rich in protein actually contain L-cysteine in small quantities. Some of these foods are:

  • turkey
  • chicken
  • duck
  • yogurt
  • pork
  • eggs
  • cheese
  • sunflower seeds
  • oat bran; and
  • legumes; among others

The body uses the amino acids methionine and serine to manufacture L-Cysteine. However, to do the same successfully, your body also needs vitamins B6 and B12, as well as folate in adequate amounts.

These vitamins are found in many foods such as (but not limited to) lentils, beans (especially pinto beans and chickpeas), spinach, bananas, avocado, liver and wild-caught tuna and salmon.

Additionally, you can also try to make the following recipes to give your cysteine levels a boost:

  • Beef Stew
  • Crockpot Chicken Recipes
  • Coconut Yogurt and Chia Seed Smoothie; and
  • Turkey Meatball Soup

L-Cysteine Supplements And Dosage

L-Cysteine is available in nutritional supplements in the form of NAC, and is recommended by many researchers for treating a variety of diseases. It is also used for a variety of other reasons, from replenishing the cells' glutathione levels and preventing oxidative damage, to inhibiting the production of cytokines, which are inflammatory substances that cause infections and respiratory problems.

L-cysteine is available in the following forms:

  • NAC aerosol spray: Used to treat respiratory as well as pulmonary problems, NAC aerosol sprays must be taken under a doctor's guidance.
  • Cysteine/NAC capsules and tablets: These are taken mainly to protect general health and antioxidants. While the normal daily dosage is 500 milligrams, adults with respiratory illness can take between 200–600 mgs, twice daily.
  • COPD: The normal daily dose for this is 600 mgs, twice daily
  • NAC liquid solution
  • NAC topical solution; and
  • L-cysteine powder

You may also take multivitamins and/or B-complex supplements to ensure that you receive your required dose of vital B-vitamins when you are taking NAC.

General Precautions To Be Taken While Consuming L-Cysteine

Taking L-Cysteine in very high doses (i.e. higher than 7 gms.) can adversely affect human cells. You must, therefore, keep thorough track of your dosage and only take NAC supplements under your healthcare provider's expert guidance, particularly if you take them for treating chronic illnesses and conditions.

Additionally, you must not take NAC supplements if you are already using medications which suppress the immune system's functioning, anti-fungal medications such as oxiconazole, high-blood pressure treatment medications such as nitroglycerin and isosorbide, or activated charcoal.

Potential Side Effects Of L-Cysteine

While L-Cysteine supplements are generally safe, some side effects such as headache, dry mouth, dizziness, vomiting and nausea may be present.

If you happen to experience these symptoms, you must speak to your healthcare provider immediately and determine whether or not you have any allergies and change your dosage accordingly.

Guide To L-cysteine Review Summary

Valued for its capacity to increase your body's glutathione levels AKA the “mother of antioxidants,” L-Cysteine itself is also an antioxidant that has a variety of other benefits such as boosting brain and lung function, and promoting liver detoxification, among others.

Ironically though, L-cysteine is one of those amino acids that are available in extremely small quantities to make glutamine, which makes it all the more important for you to make sure that that your body gets enough of it, despite it being classified as non-essential.

Cysteine is naturally found in foods that are rich in protein, such as turkey, chicken, duck, beef, egg yolks and yogurt. Additionally, it can also be taken in the form of supplements, where it is found in the form of NAC. According to many researchers, it serves as a great treatment for many illnesses.

NAC, however should always be taken in normal doses (approximately five to six hundred milligrams per day) as it can be very toxic for the blood, if taken in larger quantities. While they are generally safe, they may sometimes have side effects such as headache, vomiting and nausea.

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