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The Overlooked Compound That Saves Lives

May 2010

By Julius Goepp, MD

Innovative Strategies to Combat Kidney Disease

N-acetyl Cysteine

For more than three decades, a safe, low-cost compound has provided millions of people relief from the coughing, wheezing, and thick phlegm associated with cold and flu. Of course, pharmaceutical companies long ago co-opted it for profit by incorporating it into various patented drugs.

The sad consequence is that most aging individuals have never heard of it. Even many doctors remain unaware of its potential role as a frontline defense against some of today’s most deadly public health threats, including:

  • Acetaminophen toxicity and acute liver failure: the number one cause of acute liver failure in the United States.1
  • Influenza: whose victims are primarily aging individuals—three quarters of all flu-related deaths occur in the elderly.2
  • Chronic obstructive pulmonary disease: the fourth-leading cause of death in the United States (includes emphysema and chronic bronchitis).2
  • Helicobacter pylori: the bacterial culprit behind stomach ulcers, and a potentially lethal pathogen closely linked to malignant gastric cancer, the second most frequent cause of cancer death worldwide.3

Fortunately, renewed clinical interest in its broad-spectrum benefits is yielding fresh data on promising interventions for this safe, effective compound.

In this article, you will discover the latest research on N-acetyl cysteine (NAC), a readily available, inexpensive amino-acid derivative with four decades of scientific validation. You will learn of its role in restoring intracellular levels of one of the body’s most powerful antioxidant defenses, glutathione (GSH). You will also find out how 600-1,800 mg of NAC daily may act as an effective intervention against a constellation of chronic, degenerative diseases, including impaired glucose control and cancer.

What you need to know

  • Long relegated to infrequent use in unusual circumstances, the amino acid-derived compound N-acetyl cysteine (NAC) has drawn increased scientific attention.

  • NAC replenishes levels of the intracellular antioxidant glutathione (GSH), which is often deficient with advancing age and in chronic illness.
  • NAC also regulates expression of scores of genes in the pathways that link oxidative stress to inflammation.
  • These dual effects give NAC a unique role in the prevention and treatment of many common diseases, both acute and chronic.
  • NAC can protect against avian influenza and more common seasonal flu symptoms.
  • NAC reduces the frequency and duration of attacks of chronic obstructive pulmonary disease (COPD) and may slow the clinical course of idiopathic pulmonary fibrosis (IPF).
  • NAC protects tissues from the effects of exercise-induced oxidative stress, adding value and safety to your workout.
  • NAC improves insulin sensitivity in people with some of the most difficult-to-treat metabolic disorders.
  • NAC blocks cancer development at virtually every step in the process, and through multiple mechanisms, making it an important cancer chemopreventive agent.
  • NAC fights the stomach infection Helicobacter pylori on two fronts, inhibiting the organism’s growth while reducing production of inflammatory cytokines that can lead to gastritis and cancer.
  • Though most individuals gain benefits from 600-1,800 mg/day, clinical studies have found that doses of up to 2,000 mg/day are safe and effective. A recent study demonstrated the safety of 2,800 mg/day for 3 months in patients with COPD.23

An Underutilized Intervention

NAC is a slightly modified version of the sulfur-containing amino acid cysteine. When taken internally, NAC replenishes intracellular levels of the natural antioxidant glutathione (GSH), helping to restore cells’ ability to fight damage from reactive oxygen species (ROS).

NAC has been used in conventional medicine for more than 30 years, primarily as a mucolytic (mucous-thinner) inhaled to manage conditions such as cystic fibrosis, in which mucous is abnormally thick and tenacious. While there is little in the scientific literature to support its use as an inhalant, NAC administered in this form remains highly popular among experienced pulmonary speclialists.4,5

NAC given intravenously or orally, on the other hand, saves lives every year as a treatment for acute poisoning with acetaminophen-containing pain-relieving drugs. Acetaminophen is sold as Tylenol® and combined with other drugs to create analgesic compounds, including Vicodin® and Percocet®.6 Overdoses with acetaminophen are the number one cause of acute liver failure in the United States.6-8 Too much acetaminophen overwhelms the body’s glutathione reserves, which creates widespread and irreversible liver damage. NAC quickly restores protective levels of glutathione, averting catastrophe.7

Beyond this particular application, NAC has remained a relatively obscure and poorly understood compound until quite recently. Scientists all over the world are now beginning to understand just how vital glutathione metabolism really is, and how many disease states involve glutathione deficiency.9 According to Stanford University’s Dr. Kondala R. Atkuri, “NAC has been used successfully to treat glutathione deficiency in a wide range of infections, genetic defects and metabolic disorders, including HIV infection and COPD. Over two-thirds of 46 placebo-controlled clinical trials with orally administered NAC have indicated beneficial effects of NAC measured either as trial endpoints or as general measures of improvement in quality of life and well-being of the patients.”9

Multitargeted Regulation of Gene Expression

Multitargeted Regulation of Gene Expression

Much of NAC’s beneficial activity derives from its capacity to modulate expression of genes for myriad signaling molecules in the inflammatory response.10-12 NAC inhibits expression of pro-inflammatory cytokines following exposure to bacterial cell components and infection with influenza A virus.13,14 NAC suppresses the “master signaling molecule” nuclear factor-kappaB (NF-kB), which in turn prevents activation of multiple inflammatory mediators.15,16 NAC also regulates the gene for COX-2, the enzyme that produces pain- and inflammation-inducing prostaglandins in a wide array of chronic conditions.17

NAC’s ability to replenish the intracellular glutathione supply and mitigate oxidative damage is a separate and equally powerful mechanism that affords protection against DNA damage and cancer development, even in smokers.18 NAC’s inhibition of inflammatory cytokine production is another mechanism credited with cancer reduction in various body tissues.19

Gene expression modifications induced by NAC may also help reduce the acute oxidant-provoked inflammatory response following exercise, making vigorous activity safer and even more beneficial.20 Finally, obesity-associated insulin resistance, which arises from production of inflammatory signaling molecules in fat cells, can be sharply mitigated by NAC through regulation of their genes.21,22

The recent explosion of scientific evidence for NAC’s multi-targeted health benefits is matched only by the willful ignorance of the mainstream medical community. Some even question its safety, despite nearly 40 years of use in a variety of clinical conditions, which have established the safety of this compound, even at very high doses and for long-term treatments.18 One study demonstrated the safety of 1,800 mg per day for 142 days, while another study demonstrated the safety of 2,800 mg per day for 3 months.23

Here is a selection of the most compelling information about NAC from the global scientific community—information that should convince even skeptical mainstream physicians.

Potent Influenza Protection

H5N1 influenza, or bird flu, is a lethal and potentially pandemic infection that produces the massive release of inflammatory mediators aptly called the “cytokine storm.”24 Other more common forms of influenza also act by triggering massive cytokine releases that inflame vulnerable lung tissue. In early 2010, it was discovered that NAC offers dual protection against bird flu. It inhibits both virus replication and expression of pro-inflammatory molecules in cells infected with H5N1 virus, holding out the promise of effective protection in the event of a global avian flu pandemic.13

Potent Influenza Protection

NAC has also proven effective against seasonal influenza and flu-like illnesses. In a large study of older adults who took 600 mg twice daily for 6 months, only 25% of those experienced influenza-like episodes, compared with 79% in the placebo group.25 Even those with flu symptoms experienced a significant reduction in illness severity and length of time confined to bed. All subjects tolerated the treatment well. The study’s lead author, Dr. Silvio de Flora, commented that “Administration of N-acetyl cysteine during the winter, thus, appears to provide a significant attenuation of influenza and influenza-like episodes, especially in elderly high-risk individuals.”25

Influenza is a complex disease with multiple targets, most notably inflicting damage to lung tissue through extreme oxidative stress and inducing genes for a large variety of inflammatory mediators.26,27 At the microscopic level the destruction is vivid. The influenza virus causes such intracellular turmoil that the term “cell boiling” has been used to describe the devastation.28 But pretreatment of cells with NAC significantly offsets these effects, reducing the oxidative and inflammatory burden within lung tissue through multiple mechanisms.26,28-30

NAC has now been shown to protect laboratory mice from lethal influenza infection, synergistically enhancing the effects of several common antiviral medications.31,32 And a nutrient mixture containing NAC, green tea extract, certain amino acids and micronutrients had powerful antiviral effects in cultured cells, rivaling those of prescription flu drugs such as amantadine and oseltamivir (Tamiflu®).33,34 The NAC-based mixture actually affected viral replication for a longer period than did the drugs.34

In the words of prolific medical theorist Mark F. McCarty, “The most foolproof way to promote survival in epidemics of potentially lethal influenza is to target… intracellular signaling pathways which promote viral propagation or lung inflammation.”30 McCarty goes on to cite NAC’s benefits as a multitargeted supplement with precisely those attributes. NAC at doses of 600 mg twice daily may significantly reduce the risk of a devastating bout of influenza.

NAC and Pulmonary Arterial Hypertension: A Real Risk?

N-acetyl cysteine (NAC) produces numerous beneficial effects in many human tissues both by supporting natural antioxidant systems and by favorably affecting expression of genes involved in the inflammatory response.

A 2007 study in laboratory mice, however, has raised a theoretical concern that chronic NAC administration in those animals might produce a condition called pulmonary arterial hypertension.76 Here is a review of that study and some reassuring facts:

The Issue

Pulmonary arterial hypertension (PAH) is an elevation in blood pressure in the arteries leading from the heart to the lungs. It is one of the consequences of chronic hypoxia (lack of sufficient oxygen) that occurs in a number of chronic cardiovascular and pulmonary (lung) diseases. It also arises in people with obstructive sleep apnea.77-79 It is a rare condition, but when it occurs it can be difficult to detect and may be fatal if untreated.79 Its causes remain unclear, but they seem to involve signaling molecules produced during hypoxia; some of those molecules include those involved in detecting and responding to oxidative stress.80

The Concern

Scientists at the University of Virginia School of Medicine were studying the molecular signaling involved in hypoxia-related development of PAH when they observed what seemed to be a concerning finding: mice treated with NAC over periods of 3 weeks were developing PAH that mimicked the effects of chronic hypoxia.76 The scientists were not studying the effects of NAC itself; they were simply using it to measure other nitrogen-related transfer reactions in blood. And the doses they used correspond to a human dose of about 20 grams (20,000 mg) per day—far above any known supplement recommendation. Nevertheless, parts of their report were cited in one commentary as raising “the concern that chronic NAC therapy may induce similar vascular pathology in patients.”81

Is this a realistic concern, or is it a laboratory anomaly? Here’s the evidence to date.

The Evidence

The Virginia team’s mouse study was published in 2007. Now, nearly 3 years later, there has not been a single additional publication connecting NAC therapy with PAH in either animals or humans. In reality, a substantial amount of science both before and after the 2007 report suggests just the opposite—that NAC may be instrumental in reducing, not increasing, the oxidant-induced blood vessel changes that occur in PAH. Here are the highlights:

  • In one of the original animal studies demonstrating that oxidative stress contributes to development of PAH induced by hypoxia, NAC actually reduced the heart and lung changes that lead to PAH, in part by reducing toxic peroxide molecules.80
  • NAC, given before and at the beginning of experimental hypoxia, was effective at preventing PAH, including deadly heart muscle changes, in laboratory rats.82
  • NAC protects experimental animals’ lungs from the acute lung injury caused by a variety of mechanisms involving hypoxia, oxidant stress, and inflammation, through its joint antioxidant and anti-inflammatory actions.83,84
  • A study of human volunteers revealed that NAC supplements at 1,800 mg/day increased the healthy respiratory response to hypoxia,85 which normally declines strongly with age and may contribute to PAH.86 Although this study was cited by the Virginia group as supporting their concern about NAC inducing PAH, no such evidence is presented in the human study, and in fact the authors conclude that NAC treatment “may be useful for elderly subjects and for patients who have other conditions with an oxidative shift… such as coronary heart disease and malignant diseases.”85

The Recommendation

There have been no further publications supporting this one-time observation made in an animal model using doses 10-20 times those suggested for long-term human supplementation. No human study has uncovered any evidence for a similar effect in humans. By contrast, there have been numerous studies demonstrating human benefit from NAC supplementation at moderate doses (1,200-1,800 mg per day) over the course of nearly 4 decades. At this point the known benefits of NAC appear to outweigh any potential risks. As with all supplementation, people should communicate clearly with their healthcare providers about how supplements and medications might work jointly to influence their health.