What Is NAC Supplement?
N-Acetylcysteine (NAC) is a prodrug to L-cysteine, meaning that L-cysteine is the result of the body metabolizing NAC. L-cysteine aids in the production of glutathione, which is a very important antioxidant found in the body. However, glutathione is highly digestible and so disappears from the body quickly. This is where NAC supplementation helps by increasing L-cysteine in the body, which then aids in producing more glutathione faster than it can be depleted. 
NAC Capsules vs. Powder
Whether NAC is consumed in powder form or capsule form, the benefits are exactly the same. However, the capsule form does offer a couple of benefits over the powder. Consuming NAC in capsule form allows you to take the supplement without experiencing the taste or smell of the powder, which is slightly sulfurous. Additionally, each capsule contains a pre-measured dose of NAC, so no scale or scoop is required to get the correct dosage.
NAC Supplement Benefits
Reduce Habitual Urges
Habit-forming urges can cause a decrease in the bodyâ€™s cystine-glutamate exchangers in brain nuclei. It is this decrease that is implicated in causing these urges to become a habit. NAC supplementation can be used to augment cystine-glutamate exchangers and reverse their decline, subsequently reducing the habitual urge. [1,3]
Reduce Mineral Bioaccumulation
The body retains some minerals that are harmful to us. An example of this is the retention of lead. One study found that after supplementing with NAC for three months, workers who were exposed to occupational levels of lead had their red blood cell lead accumulations reduced, as well as an improvement in the glutathione status of red blood cells. 
Improve Mood and Reduce Stress with NAC Supplements
NAC supplementation can also lead to an increase in mood, as it stimulates the release of dopamine within the brain.  Dopamine is a neurotransmitter that controls the brainâ€™s reward and pleasure centers, and boosted levels of dopamine can help to improve mood. A reduction in the symptoms of stress is another benefit of NAC supplementation, as one study found that supplementing with NAC offered a reduction in nail-biting associated with stress, while another study found the same with regards to skin picking. [6,7]
NAC Supplement Side Effects
Reported side effects include nausea, diarrhea, vomiting, and constipation.
N-Acetyl L-Cysteine Supplement Dosage
The recommended dosage is one capsule (500mg) daily. Do not take with activated charcoal, as charcoal can reduce the absorption of NAC by at least 39%.