High cysteine is associated with age, poor dietary habits, and disease. Cysteine can be affected by factors such as age and gender, and will be lower on average in women than in men, and can also be caused by genetic defects that lead to enzyme deficiencies that result in high cysteine. Poor lifestyle habits are also a common cause of high cysteine. Many people eat a diet high in protein foods, or smoke or drink alcohol, which can lead to a deficiency of folic acid, which can also cause high cysteine. High cysteine is also related to physical diseases, such as chronic renal insufficiency, hypothyroidism, and coronary heart disease. Treatment can be improved by supplementing with folic acid and eating a diet of potatoes, avocados and bananas to help relieve the condition.