There’s no doubt NAC offers plenty of benefits. But is it safe for everyone?
We explain the numerous benefits of N-Acetyl-Cysteine, natural sources, how to choose the best NAC supplements in the UK, and when NAC is not safe to take.
What is NAC or N acetyl cysteine?
Cysteine is an amino acid, found in some foods and also made within the body using building blocks from other protein foods including eggs, cheese and meats. At times, our demand for Cysteine increases and our bodies can struggle to make enough.
Enter N-Acetyl Cysteine, or NAC, the supplement form of Cysteine. This form is acetylated (fermented) to make it easier to absorb, and to make the supplement stay fresh for longer.
It goes by many names, including N-acetylcysteine, acetyl cysteine, N-acetyl-L-cysteine and NAC.
NAC is a compound that includes sulphur, which is why it can have an eggy smell. This doesn’t mean it’s gone off. It’s just a characteristic of the active compound. If you dislike the eggy smell, you can leave your NAC capsules in the open air for a while before you take them.
Key Points
NAC supplements are a form of cysteine, an amino acid that we can get from certain foods, or make in our bodies from digested protein-rich foods that we eat. It contains sulphur and may have a slight smell.
The effects and benefits of NAC supplements
N-Acetyl-Cysteine has wide-reaching benefits in the human body. Some are well-proven, while other claims are subjects of research and a few have no evidence to back them up.
NAC Can Clear Thick Mucus with Colds and Coughs
Strength of evidence: Proven / Widely Accepted
Feeling bunged up? Possibly top of the list of NAC benefits is that it can dissolve mucus: substances that can do this are called ‘mucolitics’. This makes NAC marvellous for clearing a blocked nose and helping to clear chesty coughs.
This use of NAC is fully proven, and it’s a licensed medicine in the UK that’s used for this purpose by the NHS. Doctors in the UK prescribe it, under the brand name NACSYS, for people with long-term congestive lung diseases including COPD and pulmonary fibrosis. This medicine comes in the form of fizzy tablets for patients to dissolve in water.
N-AcetylCystine got a lot of attention during the COVID pandemic, when several researchers reported that it could make the illness milder and reduce the likelihood of death.
N-Acetyl Cysteine Detoxes Paracetamol
Strength of evidence: Proven / Widely Accepted
NAC is widely used by UK doctors in emergency situations to save people who have had a paracetamol overdose. NAC can reduce or completely prevent liver damage from paracetamol (called acetaminophen in America). Of course, always seek urgent medical attention in cases of drug overdose.
NAC helps your liver to cleanse paracetamol from the body without reducing its effectiveness as a painkiller in any way. This is the key to another of the best NAC benefits, as it’s a great detox companion and protector of your liver if you’re relying on paracetamol or Lemsip (which contains has paracetamol) to get you through the flu or a nasty cold.
Research also suggests the cysteine plays a role in detoxing other poisons including mercury, cadmium, lead, arsenic, and cyanide.
Antioxidant Support from N-Acetylcysteine
Strength of evidence: Strong Evidence / Widely Accepted
NAC is a precursor to glutathione, a powerful antioxidant in the body. By boosting glutathione levels, NAC brings benefits to all our body cells by helping to combat oxidative stress and neutralise free radicals. This is important during infections, intense exercise and times of stress.
NAC May Benefit Cardiovascular Health by Thinning the Blood
Strength of evidence: Strong Evidence
NAC has one effect of thinning the blood, an effect which may be a benefit for some people but not for others. This effect can reduce the risk of blood clots or thromboses forming in the veins, but may mean it’s not suitable for people who are already taking blood-thinning medication. It’s also claimed it improves blood circulation.
NAC may also protect the cells that line blood vessels, helping to prevent hardening arteries. NAC’s antioxidant properties may also offer benefits to cardiovascular health.
NAC the Workout Buddy for Better Muscle Recovery and Growth
Strength of evidence: Moderately Strong Evidence
NAC can benefit athletes and fitness enthusiasts by improving post-exercise recovery times and muscle performance. During intense physical activity, oxidative stress and free radicals can impair muscle function and hinder recovery. NAC helps counteract these effects by supporting glutathione production, which reduces oxidative muscle damage and helps synthesise proteins for muscle growth after a workout.
NAC The Miracle Hangover Cure
Strength of evidence: Strong Evidence (see additional links below)
Do you ever crave that classic UK breakfast of eggs and bacon the morning after a night of heavy drinking? Have you ever tried a sketchy hangover cure that includes raw egg? These are foods rich in the cysteine which our bodies use to help eliminate alcohol. NAC can give you the same benefits without the grim recipes! Some people fend off a hangover by taking one NAC supplement before going to bed, and another in the morning, to detox alcohol and acetaldehyde.
How does it NAC help the liver metabolise and excrete alcohol? Alcohol is mainly metabolised in the body by an enzyme called ‘alcohol dehydrogenase’ which first changes alcohol into acetaldehyde. NAC supplements help create glutathione, which detoxifies this acetaldehyde in the liver by binding with it. This detoxification reaction, boosted by NAC, helps to reduce the harmful effects of acetaldehyde accumulation in the body, which is the cause of hangovers and liver damage.
Fertility Benefits from NAC Supplements
Strength of evidence: Medium Evidence / Subject of Research
NAC may offer benefits for both men and women when it comes to fertility. It’s still being researched to understand how this works, but scientists claim to have found that NAC can encourage more regular ovulation in women by balancing luteinising hormone (LH), potentially promoting regular ovulation. It’s been found to help female fertility in other ways, too. Some research suggests it can also help male fertility by improving sperm quality and motility.
Can NAC Beat Cravings for Cigarettes, Vapes and Recreational drugs?
Strength of evidence: Fairly Strong Evidence
NAC is being widely researched for its beneficial ability to take away cravings for a long list of recreational drugs, from nicotine in cigarettes and vapes to cannabis and cocaine. It’s thought that this works by taking away the “buzz” that they trigger. Whilst this is still under investigation, it’s getting a lot of attention in the world of medical research because of the far-reaching health benefits it might bring about. Several trials have found that NAC supplements can stop cravings more effectively than placebos.
N-Acetlycysteine to Benefit Brain Health?
Strength of evidence: Medium Evidence
Some research claims that NAC supplements can help normalise levels of glutamate, an important neurotransmitter in the brain. Glutamate is involved in processes related to learning, memory, and overall cognitive function. Glutamate is essential but too much of it results in damage to brain cells. If NAC can stabilise glutamate at healthy levels, this could turn out to be an important health benefit.
NAC as a Beauty Supplement?
Strength of evidence: No Evidence / Unfounded Claim
L-cysteine is said on many websites to be an important building block for keratin in healthy hair, nails and skin. There is no evidence of this. A few pieces of research have concluded that the keratin in sheep’s wool is built partly from L-cysteine, but there’s no evidence at all that NAC supplements can bring about any benefits to human hair.
Key Points
NAC offers clinically proven and widely accepted benefits in dissolving thick mucus from the airways including the lungs and nose, and treating paracetamol overdose. It’s also known to thin the blood and improve circulation, reducing the risk of blood clots. It may also improve workout results, relieve hangovers, boost fertility for men and women, and stop cravings for addictive drugs including tobacco.
What could increase my need for NAC?
When our bodies can’t synthesise cysteine fast enough to meet demand, toxins may accumulate in our bodies or oxidative tissue damage can begin. We might experience a hangover, muscle damage, a blocked nose or harm to our cardiovascular system. In these situations, we can probably benefit most from taking NAC supplements.
Certain factors increase our requirement for cysteine:
- Our need for cysteine increases greatly during intense exercise, to produce the antioxidant glutathione.
- We need extra cysteine when we’re detoxing medicines including paracetamol, other toxins, and alcohol.
- Cysteine dissolves thick mucus, so our bodies can use a lot extra when we have chesty coughs, colds and flu.
Some factors slow down our body’s natural ability to make cysteine:
- The ability to synthesise cysteine and glutathione decreases with age.
- Our bodies make cysteine from protein foods like meat, eggs and dairy foods, so vegans and vegetarians tend to get less from their diet.
Key Points
We may be able to benefit more from NAC supplements when suffering from illnesses that cause thick mucus, after workouts, in older age or if we eat low animal-protein diets.
The best natural sources of NAC or Cysteine
L-cysteine, the natural form of NAC, is a semi-essential amino acid. This means that whilst we can synthesise it in our bodies, we can also eat it in various food sources. Eat a balanced diet with a variety of protein sources, including both animal and plant-based options, since this is how you can meet your body’s L-cysteine needs. It is more abundant in animal sources than vegetable options.
Here are some natural food sources of L-cysteine:
- Meat and Poultry: Chicken, turkey, and other meats are rich sources of L-cysteine.
- Eggs: Eggs, particularly the whites, contain a lot of L-cysteine.
- Dairy Products: Dairy items like cheese, yoghurt, and milk also contain L-cysteine.
- Garlic and Onions: Both garlic and onions are sulphur-rich foods that contribute to the production of L-cysteine in the body.
- Sunflower Seeds: Sunflower seeds are a plant-based source of L-cysteine.
- Red Peppers: Certain vegetables, such as red peppers, contain L-cysteine.
- Broccoli and Brussels Sprouts: These vegetables are part of the cruciferous family and provide L-cysteine.
- Oats: Oats and oat-based products contain some L-cysteine.
Key Points
Cysteine is most abundant in animal foods including meat, eggs and dairy products. It can also be found in certain vegetables.
What to look for in the best NAC supplements in the UK
Look for the standard dose prescribed by UK doctors, which is 600mg of NAC per day. This is strong enough to be effective, without being too strong.
NAC reacts with oxygen and moisture, so avoid buying products in bags and pouches because they don’t have a good enough moisture barrier. The best NAC supplement packaging is a double-sealed rigid plastic bottle that you can re-close tightly. These bottles can be 100% recyclable.
Steer clear of unnatural preservatives, flavourings or allergens. NAC capsules can benefit from a small amount of filler which can absorb any humidity and keep the NAC from degrading, but there’s no need for nasties like maltodextrin, magnesium stearate, microcrystalline cellulose, dicalcium phosphate, or any other unnecessary additives. Natural rice flour works just as well.
Check that you are buying a NAC supplement manufactured in the UK to controlled, high national standards. Positive signs to look for include BRC accredited grade AA manufacturing facilities, GMP manufacturing standards and ingredient manufacturing in the UK.
You can easily find vegan-friendly NAC capsules that are not made using animal ingredients.
Key Points
The best NAC supplements in the UK come in airtight moisture-proof packaging, provide a dose of 600mg and avoid artificial additives, fillers or bulking agents. For reassurances of product quality, they should be manufactured to formal UK quality standards in accredited UK facilities.
Cautions: Who Are NAC Supplements not suitable for?
NAC is a safe supplement for most people that offers wide-ranging benefits. However, there are some people who should use it with caution or avoid it completely.
- If you are taking ANY blood-thinning medication (Warfarin for example), don’t take NAC without first asking your doctor if it’s safe for you. NAC thins the blood and may exaggerate the effect of medicine you already take.
- If you have gastritis or a stomach ulcer, NAC is likely to be unsafe for you. NAC thins mucus, and this includes the protective mucus that lines the stomach.
- NAC can trigger asthma attacks in some people who suffer from asthma.
- Be cautious about taking N-Acetyl Cysteine supplements on an empty stomach. For some people, NAC can irritate the stomach lining if they take them without eating. If you feel sick after taking NAC or suffer heartburn, stop taking it for a week or two and then only take it with food.
A few other words of advice about your NAC supplement:
- If you are taking antibiotics, ask your pharmacist if it’s alright to take NAC as well. Some antibiotics can be deactivated by NAC.
- Do not take activated charcoal along with NAC, as the charcoal will stop the NAC from being absorbed.
- Keep your NAC away from moisture, which will make it decompose.
- Store it at room temperature in a dry place, rather than in the fridge.
Key Points
NAC can thin the mucus lining the stomach so it is not suitable for people with stomach ulcers or gastritis. It also thins the blood, so people who take blood thinning medication should only use it under medical supervision.
