On Tue, 10 Apr 2001, Amadeus Schmidt wrote: > Anything more of protein resulted in more excretion, suggesting usage as > fuel. Where I can't see a advantage from - but more work for the kidney. > Or, from more protein maybe more short-lived derivates from certain amino > acids could be made. Like NO or serotonin. This is the problem. You are making two unwarranted assumptions. First, you are assuming that there is something problematic about using protein as fuel, but there is no evidence that this is the case. The most that can be said is that it is problematic to use protein as the *only* fuel. There is no evidence that "more work of the kidney" is harmful. The second assumption is that the other benefits of additional protein--which you mention--are not significant enough to justify the use of more concentrated protein sources. It has become clear, for example, that NO is indeed an important protein metabolite, and since NO requires substantial amounts of arginine, the best way to get it is to eat meat. Yes, you could get it from peanuts, but you'd need to eat large amounts of them, and in the process you'd have other problems. It's also very interesting that to achieve a balance of insulin and glucagon, a substantial amount of protein is needed, a lot more than what is needed simply to achieve nitrogen balance. Possibly related to this is Wolfe's research indicating that higher protein intake improves blood lipids. Finally, there is also evidence that greater amounts of animal protein have a protective effect against osteoporosis, for reasons that are not yet clear. I think you have demonstrated that we can get by on less protein. There are good reasons to believe, however, that we thrive on more protein, especially animal protein. By avoiding animal protein, you probably avoid using much protein as fuel, but I'm unaware that there is any known advantage to this avoidance. At the same time, you limit your body's ability to synthesize NO from arginine, because most plant proteins are poor sources of arginine, and you're not getting that much anyway. You are making it harder to achieve a balance between insulin and glucagon, and you may be increasing your risk of osteoporosis. And you are almost certainly bringing about elevated homocysteine levels (http://www.sciencenews.org/20010113/food.asp ). If we look at the whole picture concerning proteins, and not just the nitrogen balance tests, it's clear that there are more reasons to consume animal protein than there are reasons to avoid it. Even though we are equipped to survive in conditions of extreme protein scarcity, it doesn't seem like a good idea to inflict such conditions on ourselves. And yes, a similar point might be made about carbohydrates. Todd Moody [log in to unmask]