The Legend of Zelda features milk as a recurring item through the series that restores Link's hearts, which would make the games a lot tougher if Link was lactose intolerant. From basic, plain milk to Chateau Romani or the milk used in Breath of the Wild recipes, Link consumes a lot of dairy throughout the duration of the games. Milk in Legend of Zelda can be a savior for players, refilling their heart containers in the middle of dungeons.
Legend of Zelda games take place at different points on a timeline revolving around incarnations of Link and Zelda. Many Zelda games include variations of similarly themed dungeons and different iterations of the same characters and items tailored to fit the game's position on the Zelda timeline. Some items have variations that are disappointing, like Ocarina of Time's Mask of Truth, while other items manage to maintain their usefulness across Zelda titles and remain worthwhile to get and have in Link's inventory.
Items that refill Link's heart containers like milk and fairies are particularly useful in every game they show up in because it can mean the difference between completing a difficult dungeon or dying and returning to the last save point. Milk and milk items are especially great when Link has only a few heart containers in games like Ocarina of Time, where milk will return 5 hearts and bottles hold 2 servings. Milk is generally easy to obtain in Zelda as well, often being available for purchase with Rupees or gathered. Given the early-game benefits of milk, the Legend of Zelda games would be a lot more difficult if Link couldn't capitalize on one of the most abundant health items.
Legend Of Zelda: The Difficulty Of Lactose Intolerant Link
Lon Lon Ranch in Legend of Zelda can be a boon to Link as he begins his journey, but if he was lactose intolerant, it would bring more harm than help. In this scenario, milk would likely reduce Link's hearts rather than refill them, given how uncomfortable the side effects of drinking milk are when somebody has such a condition. At best, Link could be given a reduction in movement speed or attack damage debuff from milk. At worst, Link could take damage from drinking milk and receive a stamina debuff.
Milk is a recurring, beneficial item in Legend of Zelda, which leads to Link drinking a lot of it. Nintendo's developers are kind enough to not make a Zelda title with a lactose intolerant Link, even though it would be a good way to throw off players who are used to milk being helpful, given that the item is nearly as iconic as Zelda games starting with Link waking up. Alternatively, a game mode with lactose intolerant Link could be a fun option to slightly increase the difficulty in Legend of Zelda.