Blood vessels constrict at high altitude, which increases lung blood pressure and contributes to AMS. Symptoms include nausea, vomiting, decreased energy levels, fatigue and anxiety. Beetroot juice, which is high in nitrates, increases the production of nitric oxide by the blood vessels, which helps the blood vessels relax and return to normal function. AMS can occur as low as 5,000 feet. Most people experience symptoms at 10,000-12,000 feet. Meds such as acetazolamide and dexamethasone are currently used to treat and prevent AMS. Beetroot is a healthier alternative.