There is no question that consuming sufficient protein is essential to optimal health. However, this does not imply “the more, the better.”
Health experts are discovering big problems with high-protein, low carbohydrate diets: When carb intake drops as low as 10-15% of calories, a condition called ketosis may result. This condition can also occur in starvation or in diabetes mellitus, where there simply isn’t enough carbohydrates to fuel the brain. The brain depends on glucose as its fuel, and doesn’t do well under these conditions. Ketosis can lead to dizziness, headaches, nausea, fatigue, sleep problems and bad breath. If continued, it can escalate and result in dehydration, gout, low blood pressure (hypotension), electrolyte imbalances and possible kidney and liver damage.
High protein diets are often deficient in components that protect us against disease - phytochemicals, fiber, and other protective vitamins. Diets that are very high in protein may actually provide excessive amounts of the sulfur-containing amino acids, methionine and cysteine which, in excess, may be detrimental to health. Animal protein raises blood cholesterol levels while plant protein lowers it. High protein diets have their place when people do require extra protein at times of growth (i.e. pregnancy & lactation, puberty), while healing after injury or when the fitness goal is building muscle. Even at times of increased need, the amount required tends to be less than 2 grams protein per kg of body weight.