Your friend can't get nearly enough D from foods. Batch's recommended minimum daily dose of D3 is 10,000IU. Your friend would have to eat between 5 and 10 pounds of salmon in a day to get 10,000IU (depending on whether the salmon is wild caught or farmed). More than ten pounds a day of fresh herring; more than 20 pounds of pickled herring. More than 6 tablespoons per day of cod liver oil.
Pills are a lot easier. https://www.healthline.com/nutrition/9-foods-high-in-vitamin-d#1