For swimmers and other serious athletes how much protein you actually need in your diet is a tough question. The US FDA for instance says the average adult needs at least 50g of protein/day, while the USDA says 0.8g of protein per 2lbs of body weight is a required minimum intake to maintain health. But these are widely viewed as bare minimums for inactive adults.
Recommended protein intake for athletes is often much higher. The Canadian Academy of Nutrition and Dietetics and the American College of Sports Medicine both recommend 1.2g to 2.0g of protein per Kg of body weight for athletes, while the International Society for Sports Nutrition recommends 1.4g to 2.0g “for physically active individuals” just to meet their basic dietary requirement for protein. And that's just for active people, with some sources claiming that intense exercise like swimming requires as much as 3.5g of protein per Kg of body weight each day.
So what does that really mean in terms of food? To reach a conservative goal of 1.6g of protein per Kg of body weight, a 110lbs (50Kg) athlete would need to consume 80g of protein per day. To illustrate, that would mean approximately 11oz of meats (beef, chicken, turkey, etc…), 80oz (2.5 Quarts) of milk, 5 cups of beans, a pound of sunflower seeds, or thirteen eggs every day.
Add to that the fact that not all types of proteins are absorbed equally, and elite athletes like serious swimmers need to be conscious of their protein intake, or they may risk deficiency and have trouble reaching their maximum potential.
Here’s some more guidance from the FDA on how to view protein in labels and how to understand what you’re getting in your foods.