3. Daily requirements Recommendations for vitamin C intake have been set by various national agencies: - 40 milligrams per day: the United Kingdom's Food Standards Agency -45 milligrams per day: the World Health Organization -60 mg/day: Health Canada 2007 -60–95 milligrams per day: United States' National Academy of Sciences There is continuing debate within the orthodox scientific community over the best dose schedule of vitamin C for maintaining optimal health in humans.