N-acetyl-L-cysteine

N-acetyl cysteine (C5H9NO3S) is an L-cysteine derivative that is more stable than L-cysteine. While L-cysteine is already found in the diet - mostly in lean meats - NAC is not found in the diet and must be taken as a supplement to the diet.N-acetyl cysteine is also known as NAC and acetylcysteine. As a derivative of L-cysteine, NAC is more soluble in water and therefore more bioavailable than regular L-cysteine.

Potential health benefits of NAC

NAC has antioxidant properties and is essential for the production of the powerful antioxidant glutathione

Research has found that NAC has strong antioxidant effects (1). In this function, NAC cleanses the body of harmful free radicals and neutralizes them, which can cause oxidative damage to muscle tissue, bodily organs and DNA. As an antioxidant, it can reduce oxidative stress by preventing the onset of some cancers and possibly slowing the aging process. NAC, along with two other amino acids - glutamine and glycine - is required for the production of glutathione and the replenishment of glutathione stores. Glutathione is the body's most important antioxidant and helps neutralize free radicals that can damage the body's cells and tissues. Glutathione is essential for the health of the immune system and fighting cellular damage. Some scientists even believe it may contribute to longevity (7).

Its antioxidant properties are also important for fighting many other conditions such as heart disease, infertility and some psychiatric conditions caused by oxidative stress (8). NAC helps with detoxification and may prevent liver and kidney damage NAC plays an important role in the body's detoxification processes. It can help prevent the side effects of medications and the harmful effects of environmental toxins (9). In fact, NAC is regularly administered intravenously by physicians for acetaminophen overdoses to prevent kidney and liver damage (10).

NAC has been shown in scientific studies to have beneficial effects on liver function by protecting the liver from heavy metals such as lead and mercury, as well as from damage resulting from acetaminophen use. In fact, the effects of NAC on the liver are so strong that it is now commonly used to help with liver failure resulting from drug use and hepatitis (2). NAC may also be used to treat other liver conditions due to its antioxidant and anti-inflammatory benefits (11).

NAC may help alleviate psychiatric disorders and addictive behaviors

NAC helps to regulate glutamate levels - the most important neurotransmitter in the brain (12). While glutamate is required for normal brain function, excess glutamate combined with depletion of glutathione stores can cause brain damage. This could contribute to mental disorders such as bipolar disorder, schizophrenia and obsessive-compulsive disorder (13). In people with bipolar disorder and depression, NAC may help reduce symptoms and improve overall functioning. Furthermore, research suggests that it may help in the treatment of moderate to severe obsessive-compulsive disorder (14, 15).

In addition, research conducted with animals suggests that NAC may minimize the negative effects of schizophrenia such as social isolation, apathy and reduced attention span (16). NAC supplementation may also help reduce withdrawal symptoms and reduce relapse in cocaine addicts (17, 18). Preliminary studies also show that NAC may reduce cravings for marijuana and nicotine, as well as other cravings (19, 20). For many of these conditions and disorders, there are currently limited or ineffective treatment options. NAC could be an effective aid for people with these conditions (21).

NAC can relieve symptoms of respiratory diseases

NAC can relieve symptoms of respiratory diseases by acting as an antioxidant and mucolytic. It belongs to a class of active ingredients called mucolytics or expectorants. It reacts with chemicals in mucus to make it less sticky and easier to cough up. This can clear the airways, make breathing easier and reduce symptoms of chronic bronchitis (3). As an antioxidant, NAC helps to replenish glutathione reserves in the lungs and reduce inflammation of the bronchial tubes and lung tissue. People with chronic obstructive pulmonary disease (COPD) suffer from long-term oxidative damage and inflammation of the lung tissue, which can cause airway blockages leading to shortness of breath and coughing.

NAC supplements are used to reduce COPD symptoms, mucus formation and a decrease in lung function (22, 23). In a one-year study, 600 mg of NAC twice daily significantly improved lung function and symptoms in people with stable COPD (24). Patients with chronic bronchitis can also benefit from NAC. Bronchitis occurs when the mucosal membranes in the bronchi of the lungs become inflamed, swollen and block the airways to the lungs (25, 26). By thinning the mucus in the bronchi and increasing glutathione levels, NAC can help to reduce the severity and frequency of breathlessness, coughing and respiratory attacks (27). In addition to relieving COPD and bronchitis, NAC may also relieve other lung and airway conditions such as cystic fibrosis, asthma and pulmonary fibrosis, as well as symptoms of nasal and sinus congestion due to allergies or infections (28).

NAC may promote brain health by regulating glutamate levels and replenishing glutathione reserves

The brain neurotransmitter glutamate is involved in a wide range of actions of learning, behavior and memory, while the antioxidant glutathione helps prevent age-related oxidative damage to the brain (29). Because NAC helps regulate glutamate levels and replenish glutathione stores, it may be helpful for conditions related to the brain and/or memory (30). The neurological disease Alzheimer's reduces the brain's capacity for learning and memory.

Studies conducted with animals suggest that NAC can slow the loss of cognitive abilities in Alzheimer's patients (30, 31). Parkinson's disease - another brain disorder - is characterized by destruction of the cells that produce the neurotransmitter dopamine. Both oxidative damage and reduced antioxidant capacity contribute to this disease. NAC supplements appear to improve dopamine function and reduce Parkinson's symptoms such as tremors (30).

NAC could improve fertility in men and women

About 15% of all couples who wish to have children are affected by infertility. In almost half of these cases, male infertility is the primary factor. Problems with male fertility increase when antioxidant levels are insufficient to combat the formation of free radicals in the reproductive system. The resulting oxidative stress can lead to cell death and reduced fertility. NAC has been shown to improve male fertility in some cases. One problem that can contribute to male infertility is so-called testicular varicose veins or varicocele - an enlargement of the veins within the scrotum due to free radical damage.

Surgery is the primary treatment. In a study, 35 men with testicular varicose veins were given 600 mg of NAC per day for three months after surgery. The combination of surgery and NAC supplementation improved sperm integrity and increased the rate of pregnancy by 22% compared to the control group (32). Another study of 468 men with infertility found that supplementation with 600 mg NAC and 200 mcg selenium for 26 weeks improved sperm quality (33). Researchers suggest that this combination should be considered as a treatment option for male infertility. In addition to this, NAC could improve fertility with polycystic ovary syndrome by inducing the ovulatory cycle (34).

NAC could stabilize blood glucose levels by reducing inflammation in fat cells

High blood glucose levels and obesity can contribute to inflammation in adipose tissue. This can lead to damage or destruction of insulin receptors and increase the risk of type 2 diabetes. Animal studies show that NAC can improve blood glucose levels by reducing inflammation in fat cells and improving insulin resistance as a result (35, 36). When insulin receptors are intact and healthy, they optimally remove sugar from the blood and keep blood glucose levels in the normal range. NAC may reduce the risk of heart disease by preventing oxidative damage Oxidative damage to heart tissue often leads to heart disease, which can cause strokes, heart attacks and other serious diseases.

NAC may reduce the risk of heart disease by reducing oxidative damage to heart tissue (37). NAC has also been shown to increase nitric oxide production, which helps to dilate veins and improve blood flow (38). This accelerates blood flow back to the heart and may reduce the risk of heart attack. Interestingly, an in vitro study showed that NAC in combination with green tea can reduce damage from oxidized bad LDL cholesterol, which is another contributing factor to heart disease (39).

NAC can improve immune function by increasing glutathione levels

Scientific research on certain diseases associated with NAC and glutathione deficiency suggests that NAC supplementation can improve and potentially restore immune function (40). This factor has been most studied in people suffering from HIV infection. In two studies, supplementation with NAC resulted in a significant improvement in immune function - with an almost complete restoration of natural killer cells (41, 42).

High NAC levels in the body could also suppress HIV-1 replication (43). An in vitro study suggests that in other situations of compromised immune system function, such as influenza, NAC may inhibit the ability of the virus to replicate. This may potentially lead to a reduction in symptoms and duration of illness (44). Other in vitro studies have linked NAC to cancer cell death and inhibition of cancer cell replication (45, 46).

Other benefits of NAC

NAC has many other beneficial effects on the body including protecting the colon from damage that forms from polyps (4), as well as the ability to stop the replication of several strains of HIV. Healthy adults may benefit from the use of NAC as a dietary supplement. Naturally exercising athletes may benefit from supplemental use of NAC due to its ability to protect the immune system from harmful oxidants resulting from environmental stress, normal metabolic function and intense exercise. Often the use of anabolic substances can raise liver enzyme levels above normal. Liver enzyme elevation is the sign of liver inflammation and in some cases this inflammation can lead to induced hepatitis.

Heavy users of steroids should use NAC for post-cycle therapy (along with other dietary supplements) to reduce liver enzyme levels and restore proper liver function. Supplementing with NAC may help support proper immune system function by reducing the effects of prescription medications on immune function and overall health. Supplementing with NAC may therefore be warranted if you are taking prescription medications.

Since NAC has antioxidant effects, can break up mucus structures, and has been clinically proven to reduce symptoms of acute bronchitis, it may have beneficial effects in individuals with asthma or acute bronchitis. It is possible that NAC may protect the lungs from oxidative damage, although further research is needed to test this hypothesis. Finally, NAC may prevent colon polyp formation, which is significant because processed foods - which are consumed in high amounts by most people - contribute to these formations and these very formations can lead to colon cancer and loss of bowel control.

Dosage

NAC has a low bioavailability when taken orally. The accepted daily supplement recommendation is 600 to 1,800 mg NAC (47, 48).

Deficiency symptoms

NAC is not an essential nutrient and there are no deficiency symptoms

Side effects

N-acetyl cysteine is likely safe and harmless for most adults when used as an approved medication. Side effects that may be associated with NAC use in high doses include nausea, headaches, vomiting, dizziness and abdominal pain. Research has shown that NAC can act as an oxidant when taken in high doses (5). NAC can lead to the excretion of zinc and copper - metals that are necessary for proper hormone function, so make sure you take these minerals in addition if you use NAC (6). If NAC is inhaled, it can cause swelling in the mouth, a runny nose, lightheadedness and chest tightness. People with blood clotting disorders or people taking blood thinning medication should avoid NAC as it can slow down blood clotting (49).

NAC warnings

Allergy warnings

Acetylcysteine can cause severe allergic reactions. Symptoms include:

• Difficulty breathing
• Swelling of the throat and tongue

If these symptoms occur, a doctor should be called immediately or the nearest emergency room should be visited. NAC should not be used by anyone who has ever had an allergic reaction to this drug, as NAC could be fatal to them.

Warning for people with asthma

There are concerns that N-acetyl cysteine may cause bronchial spasms in asthmatics when inhaled or taken orally. For this reason, asthmatics should only use N-Acetyl Cysteine under medical supervision.

Warnings for other groups of people

Although animal studies do not indicate risks to the unborn fetus, pregnant women should only use NAC in consultation with their doctor, as there is insufficient data on its safety during pregnancy. Breastfeeding women should only use NAC in consultation with their doctor, as the active ingredient can pass into breast milk and cause serious side effects in breastfed infants.

Interactions

N-Acetyl Cysteine should not be used in combination with the following medications:

Nitroglycerin

Nitroglycerin can dilate the blood vessels and improve blood circulation. Taking N-acetyl cysteine appears to increase the effects of nitroglycerin. This could increase the risk of side effects such as headaches, dizziness and drowsiness.

Care should be taken when combining N-acetyl cysteine with the following medications

Activated charcoal

Activated charcoal is sometimes used to prevent poisoning in people who have taken too much acetaminophen and other medications. Activated charcoal can bind these drugs in the stomach and prevent them from being absorbed by the body. Taking N-acetyl cysteine at the same time as activated charcoal could reduce the effectiveness of activated charcoal in preventing poisoning.

References

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3. Multicenter Study Group. Long-term oral acetylcysteine in chronic bronchitis. A double-blind controlled study. Eur J Respir Dis 1980;61:111:93-108.

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