Amyotrophic lateral sclerosis (ALS) is a serious rapidly progressive disease of the nervous system. The average survival from the time of diagnosis is 3 years. Apart from Riluzole, there is no effective treatment. Care of advanced ALS will have a cost of 4-8 million NOK per year

Research i.a. from the investigators department has shown that increased activity in histone deacetylation enzymes (sirtuins) together with increased access to NAD can delay disease progression. Nicotinamide riboside (NR) can increase cells' access to NAD and Pterostilben will stimulate sirtuins.

The investigators want to study whether combination therapy with NR and Pterostilben can inhibit neurodegeneration in ALS and thereby delay disease development, increase survival and improve quality of life in ALS.

In the study, the investigators will use 2 different dosages on the active treatment and strength calculations show that 180 patients are needed to show a rather weak effect. Patients will be recruited in collaboration with hospitals in Helse Vest, AHUS, Drammen, OUS and St. Olavs hospital.

Inclusion Criteria:

Arm 1 (newly diagnosed ALS patients)

• Have a clinical diagnosis of probable ALS according to the revised El Escorial criteria.
• MR of the brain and cervical spine cannot explain symptoms.
• Diagnosed with likely ALS within 6 months from enrolment and treated with Riluzole 50mg x 2
• Symptom onset no longer than 2 year prior to inclusion.
• ALS-FRC-R of 36 or more (not any item below 2).
• Age equal to or greater than 35 years at time of enrollment

Arm 2 (earlier diagnosed ALS patients)

• Have a clinical diagnosis of probable ALS according to the revised El Escorial criteria.
• MR of the brain and cervical spine cannot explain symptoms.
• Treated with Riluzole 50mg x 2.

Exclusion Criteria:

• Dementia, FTD or other neurodegenerative disorder at baseline visit
• Any psychiatric disorder that would interfere with compliance in the study.
• Use of high dose vitamin B3 supplementation within 30 days of enrollment
• Metabolic, neoplastic, or other physically or mentally debilitating disorder at baseline visit.
• Genetically confirmed mitochondrial disease
• Patients who become tracheostomized as part of the treatment of ALS
• Patients with short expected survival at the discretion of the investigator. Such cases cannot be expected to follow protocol procedures.