Vitamin C deficiency

A 45-year-old man presents to his primary care physician with a two-month history of malaise, fatigue, and heavy bruising of his legs. He has a five-year history of gastroesophageal reflux disease (GERD). Further questioning reveals that he has experienced progressively worsening nausea and early satiety in the past few months, leading to a diet consisting only of bread and water. Physical examination shows periorbital ecchymoses, perifollicular hemorrhages, and large ecchymotic areas on both legs. Which of the following measures would best prevent the most likely cause of his symptoms?