And with the increasing availability of lean meats, they make an important point. But for most Americans, high-protein diets tend also to be high in fat. And despite widespread claims by authors of low-carb diet books, all major medical and health organizations maintain that a diet high in fat can lead to heart disease, cancer and a wide variety of otherwise preventable illnesses. Many of the low-carb diet authors caution people with a family history of kidney disease not to follow their plans, but rarely do they offer any reasons for the warnings. The reasons are many.
Protein is metabolized in the liver, then excreted to the kidneys for disposal in the urine.
Everyone from former Surgeon General C. Everett Koop to organizations like the American Dietetic Association agree that increased protein load is stressful to both the liver and kidneys. Furthermore, kidney function decreases naturally with age in most Americans, whose diets are typically above the recommended percentage of protein at 12 to 15 percent. For the sake of perspective, Enter The Zone recommends a diet of 30 percent protein, and others recommend even higher percentages. Another common load of nonsense put forth by authors of low-carb diets is that sugar causes diabetes and makes you fat. The only direct relationship sugar intake has on health is its role in tooth decay.