Cysteine

Question 1

Cysteine

Answer 1

• Cysteine is a conditionally essential amino acid formed from methionine and serine in the liver (B6, B9 and B12 are needed).
• Direct food sources (most sulphur in food is in the form of protein bound cysteine): legumes, sunflower seeds, eggs, chicken
• It is a component of glutathione and is needed in the formation of Co-enzyme A and taurine
• It is the rate limiting amino acid for glutathione synthesis, so is very important for detoxification and antioxidant support.
• Cysteine is the source of sulphate (-SO 4 ), used in the phase II liver detoxification pathway sulfation (used for many drugs, steroid hormones etc.) increasing water solubility for their excretion.

Question 2

N-Acetyl Cysteine

Answer 2

N-acetyl cysteine (NAC) is a derivative of L cysteine. It is used in supplementation as it is easier to absorb:

Question 3

N- Acetyl Cysteine Functions

Answer 3

Liver Detoxificationn/ Antioxidant
Reproductive Health
Respiratory Health
Insulin Resistance

Question 4

N- Acetyl Cysteine: Liver Detoxification / Antioxidant

Answer 4

Functions:
• It is a building block of glutathione. Cysteine plays a crucial role in the body’s antioxidant defences.
• Crucial in drug metabolism in the liver (drugs deplete glutathione cysteine regenerates it).

Therapeutic Uses:
• Liver support (including heavy metal detox)
• Healthy ageing support
• Ulcerative colitis

Question 5

N-Acetyl Cysteine: Reproductive Health

Answer 5

Functions:
• Has been shown to increase sperm concentration, likely due to its
antioxidant properties.
• Positively impacts serum testosterone

Therapeutic Uses:
• Infertility

Question 6

N-Acetyl Cysteine: Respiratory Health

Answer 6

Functions:
• Expectorant properties (it breaks up mucus to aid easier elimination from
the respiratory tract).
• Mainly due to the breakage of the disulphide bonds in mucoproteins.

Therapeutic Uses
• Respiratory infections e.g. bronchitis
• Cystic fibrosis
• Asthma

Question 7

N-Acetyl Cysteine: Insulin Resistance

Answer 7

Functions:
• Increases insulin sensitivity

Therapeutic Uses:
• Diabetes mellitus
• PCOS

Question 8

N-Acetyl Cysteine: Other therapeutic uses

Answer 8

• HIV support: Associated with increased glutathione, reduced oxidative stress and enhanced T-cell count and activity.
• Neuro degenerative diseases e.g. Parkinson’s, Alzheimer’s.

Question 9

N-Acetyl Cysteine: Other applications

Answer 9

In emergency medicine, NAC is used as an antidote for paracetamol toxicity resulting from an overdose (as paracetamol is detoxified using the glutathione pathway) protecting the liver from damage.

Question 10

N-Acetyl Cysteine: Dosage

Answer 10

• Dosage: 600mg 1.5g/day (e.g. 600mg x 2 per day)

Question 11

N-Acetyl Cysteine: Drug Interactions

Answer 11

Nitro glycerine (can cause hypotension and headaches).
Caution also with insulin use.