Gannon and Nuttal's study closely reflects my personal experience during the last 3 years. Starting as a prediabetic (FBG > 100), I was able to "cure" this by modifying my diet from about 55% carbs down to 40%, and then 30%, with increases in protein and fat similar to those in their study. One difference, however, is that I experienced significant weight loss without calorie restriction. So they may want to consider that the amount of fat and muscle carried by one's body may be sensitive to the macronutrient ratios, independent of calorie intake.
Another issue is whether 30% protein is safe for bone health. My review of the literature led me to conclude that 20% was closer to optimal, with 15% being the minimum for good bone growth, and 30% producing too high an acid load, leading to bone loss.
Finally, I think they are on the right track in thinking that 30% carbohydrate will be easier for dieters to deal with. And if 20-30% is the protein target, then that leaves 40-50% fat. The interesting question then is what the nature of this fat should be?
Competing interests
none
High-protein intake and bone health
Anssi Manninen, Advanced Research Press, Inc.
1 April 2006
Kampmeier suggested that high-protein intake (30%) may have some adverse effects on bone health. It should be noted, however, that there is no scientific evidence supporting this notion. High protein intake enhances IGF-1, a growth factor that exerts highly positive activity on bone formation. Consequently, high-protein intake is, if anything, protective against loss of bone minerals. For a more detailed reviews, see the papers by Manninen [1] and Bonjour [2].
References
1. Manninen AH. High-protein weight loss diets and purported adverse effects: where is the evidence? Sports Nutr Rev J 2004;1(1):45-51.
2. Bonjour JP. Dietary protein: an essential nutrient for bone health. J Am Coll Nutr 2005;24:526S-36S.
Competing interests
None.
upper protein limit not known
Dan Kampmeier, none
10 April 2006
Manninen claims that there is no scientific evidence supporting the notion that 30% protein intake has any adverse effects on bone health, although his own review (his [1]) of the related acid load hypothesis states that "the epidemiological and clinical data addressing this hypothesis are controversial". I reached the same conclusion, and, given the controversial and often-contradictory results of a large number of studies, was unable to justify a 30% protein intake until further research has fully resolved the question of protein's acid load effects on bone health.
The major problem is that most of the studies of this issue have been done in the range of 0.7 to 1.5 g/kg, or about 10 to 20% protein intake, well below the 30% that is in question. This lower range has created a good concensus for a minimum protein intake of about 1 g/kg, or about 15% of calories, but has done little to help answer the question of what the upper limit of protein intake should be. In particular, we are missing information on the effects of high protein intake (30% or more) in elderly subjects, with normal activity levels, over an extended period of time (i.e., a group that is most likely to actually show greater bone loss rather than just a slowing of bone growth as you might see in a younger subject).
Another thing I had noticed in the cross-cultural studies of the relationship between bone health (as measured by density or fracture rate) and protein intake, was the sharp rise in the number of groups with poorer bone health as 30% protein intake was approached. In other words, there seems to be a plateau between about 15 and 25% protein intake, below and above which bone health is reduced. This wouldn't mean that 30% is always a problem, since it may be possible to offset its effects with more exercise, vitamin D, alkalinity, etc. (as was probably the case with our paleolithic ancestors). But it might mean that such a high protein diet requires greater vigilance, and a better knowledge of all the factors that can affect bone health - a knowledge that we do not yet seem to possess.
personal confirmation of results
1 April 2006
Gannon and Nuttal's study closely reflects my personal experience during the last 3 years. Starting as a prediabetic (FBG > 100), I was able to "cure" this by modifying my diet from about 55% carbs down to 40%, and then 30%, with increases in protein and fat similar to those in their study. One difference, however, is that I experienced significant weight loss without calorie restriction. So they may want to consider that the amount of fat and muscle carried by one's body may be sensitive to the macronutrient ratios, independent of calorie intake.
Another issue is whether 30% protein is safe for bone health. My review of the literature led me to conclude that 20% was closer to optimal, with 15% being the minimum for good bone growth, and 30% producing too high an acid load, leading to bone loss.
Finally, I think they are on the right track in thinking that 30% carbohydrate will be easier for dieters to deal with. And if 20-30% is the protein target, then that leaves 40-50% fat. The interesting question then is what the nature of this fat should be?
Competing interests
none
High-protein intake and bone health
1 April 2006
Kampmeier suggested that high-protein intake (30%) may have some adverse effects on bone health. It should be noted, however, that there is no scientific evidence supporting this notion. High protein intake enhances IGF-1, a growth factor that exerts highly positive activity on bone formation. Consequently, high-protein intake is, if anything, protective against loss of bone minerals. For a more detailed reviews, see the papers by Manninen [1] and Bonjour [2].
References
1. Manninen AH. High-protein weight loss diets and purported adverse effects: where is the evidence? Sports Nutr Rev J 2004;1(1):45-51.
2. Bonjour JP. Dietary protein: an essential nutrient for bone health. J Am Coll Nutr 2005;24:526S-36S.
Competing interests
None.
upper protein limit not known
10 April 2006
Manninen claims that there is no scientific evidence supporting the notion that 30% protein intake has any adverse effects on bone health, although his own review (his [1]) of the related acid load hypothesis states that "the epidemiological and clinical data addressing this hypothesis are controversial". I reached the same conclusion, and, given the controversial and often-contradictory results of a large number of studies, was unable to justify a 30% protein intake until further research has fully resolved the question of protein's acid load effects on bone health.
The major problem is that most of the studies of this issue have been done in the range of 0.7 to 1.5 g/kg, or about 10 to 20% protein intake, well below the 30% that is in question. This lower range has created a good concensus for a minimum protein intake of about 1 g/kg, or about 15% of calories, but has done little to help answer the question of what the upper limit of protein intake should be. In particular, we are missing information on the effects of high protein intake (30% or more) in elderly subjects, with normal activity levels, over an extended period of time (i.e., a group that is most likely to actually show greater bone loss rather than just a slowing of bone growth as you might see in a younger subject).
Another thing I had noticed in the cross-cultural studies of the relationship between bone health (as measured by density or fracture rate) and protein intake, was the sharp rise in the number of groups with poorer bone health as 30% protein intake was approached. In other words, there seems to be a plateau between about 15 and 25% protein intake, below and above which bone health is reduced. This wouldn't mean that 30% is always a problem, since it may be possible to offset its effects with more exercise, vitamin D, alkalinity, etc. (as was probably the case with our paleolithic ancestors). But it might mean that such a high protein diet requires greater vigilance, and a better knowledge of all the factors that can affect bone health - a knowledge that we do not yet seem to possess.
Competing interests
none