NAC is considered ‘conditionally essential’ because your body can produce it from other amino acids. It becomes essential only when the dietary intake of methionine and serine is low.

Cysteine is found in most high protein foods, such as chicken, turkey, yogurt, cheese, eggs, sunflower seeds, and legumes.

Consuming adequate cysteine and NAC is important for various health reasons, including replenishing the most potent antioxidant in your body, glutathione. These amino acids also help with chronic respiratory conditions, fertility, and brain health.