Many of the world’s people struggle to obtain enough food and enough protein to keep themselves alive, but in the developed countries, where protein is abundant, the problems of protein excess can be seen. Animals fed high-protein diets experience a too much protein overload effect, most notable in the enlargement of their livers and kidneys. In human beings, diets high in animal protein necessitate higher intakes of calcium as well, because such diets promote calcium excretion. Too much protein may also create an increased demand for vitamin B6 in the diet, which the body requires to utilize the protein. The higher a person’s intake of animal-protein sources such as meat, the more likely it is that fruits, vegetables, and grains will be crowded out of the diet, creating deficiencies of other nutrients.
Although protein is essential to health, the body converts extra protein to energy (glucose), which is stored as body fat when energy needs are met. Despite the flood of new protein-packed snack bars and other products in the marketplace, there are no known benefits from consuming excess or too much protein. The recommended upper limit for protein intake applies when calorie intake is adequate. Note the qualification “when calorie intake is adequate” in the preceding statement. Remember that your recommended protein intake can be stated as a percentage of calories in the diet or as a specific number of grams of dietary protein. The recommended protein intake for a 150-pound person is roughly 55 grams, or about 12 percent of their daily caloric intake. Fifty-five grams of protein is equal to 220 calories and equals 11 percent of a 2,000-calorie intake, which is reasonable for a 150-pound active person. If this person were to drastically reduce his or her caloric intake to, say, 800 calories a day, then 220 calories from protein is suddenly 28 percent of the total. However, it is still this person’s recommended intake for protein, and a reasonable intake. It is the caloric intake that is unreasonable in this example. Similarly, if the person eats too much protein or too many calories, say, 4,000, this protein intake represents only 6 percent of the total caloric intake, yet it is still a reasonable intake. It is the caloric intake that may be unreasonable.
Thus, it is important to be careful when judging protein intakes as a percentage of calories. Always ask what the absolute number of grams is, too, and compare it with the recommended protein intake in grams. Recommendations stated as a percentage of calories are useful only when food energy intakes (calories) are within reason.