Amazoniac
Member
What follows is regarding the 'adabolic ceiling', not optimal intake:
- Update on maximal anabolic response to dietary protein
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- Update on maximal anabolic response to dietary protein
"We previously presented data supporting the perspective that the maximal total anabolic response increases linearly in relation to the amount of amino acid or protein intake [18,19,33-35]. These data did not show a plateauing in the gain in the net balance between protein synthesis and breakdown as the amount of intake increased. It is reasonable to assume that there must be some upper limit to the anabolic response to the amount of dietary protein in one meal. There is some level of protein intake that maximally stimulates protein synthesis, and the rate of protein breakdown can only be suppressed to a certain extent because a negative rate of protein breakdown is impossible. Thus, the short answer to the question -- Is there a maximal anabolic response to dietary protein? -- must be yes. The amount of dietary protein that elicits the maximal anabolic response is the key point of relevance to protein nutrition. In order to draw quantitative conclusions, it is necessary to evaluate current data in the context of the preceding discussion of the roles of protein synthesis and breakdown in the anabolic response, as well as the methodologies that have been used to address this issue."
"There is a theoretical upper limit to the anabolic response to dietary protein intake that is dictated by the maximal extent to which protein synthesis can be stimulated and protein breakdown can be suppressed. For the reasons discussed above, we will consider the whole body responses of protein synthesis and breakdown as the best reflection of the total anabolic response to dietary protein. We can make a reasonable estimate of the maximal whole body anabolic response from data in the literature. In our recent acute metabolic study, we observed that in the fasting state whole body protein synthesis was approximately 3.5 g/kg/day, and protein breakdown was approximately 4.3 g/kg/day although not shown explicitly in the paper [19]. Although it is well documented that the maximal increase in MPS in response to consumption of pure dietary protein or amino acids is approximately ~100% greater than the basal value [26-28], similar data are not available for whole body protein synthesis. Similarly, protein dose-response data for the response of MPS to a mixed meal containing protein are not available. Consequently, there is a degree of uncertainty regarding an assumed maximal stimulation of whole body protein synthesis. We will make the conservative estimate that the maximal percent increase in whole body protein synthesis is half as great as the response of MPS, or 50% greater than the basal value. This assumption is based on the fact that muscle is the primary target of dietary protein [4], and therefore muscle is more responsive to variations in intake than other tissues and organs. In our example, a 50% increase in whole body protein synthesis would be 3.5 g/kg/day * 0.50, or 1.75 g/kg/day. With regard to the maximal suppression of breakdown, we have previously shown that intake of a mixed meal containing protein suppressed breakdown by approximately 60% [19], and breakdown cannot be totally shut off, so we can be reasonably confident that whole body protein breakdown can be maximally suppressed to 20% of its basal value (80% suppression). This corresponds to a reduction in breakdown of 3.44 g/kg/day. When the maximal rate of suppression of breakdown (3.44 g/kg/day) is added to the maximal increase in synthesis (1.75 g/kg/day), the total maximal anabolic response is 5.19 g/kg/ day, or 216 mg/kg/h."
"However, the maximal response is not sustained for an entire day in response to a single meal. If we make the conservative assumption that the response to a single meal containing a large amount of protein to elicit the maximal anabolic response lasts for 3 h, then we calculate that the theoretical total anabolic response is approximately 3 h/meal * 216 mg/kg/h = 648 mg/kg/meal."
"The amount of protein intake required to stimulate the maximal anabolic response depends on the quality of the protein, where quality is defined by the amount and profile of EAAs, as well as the true ileal digestibility of the protein [17,36]. For the purpose of this example, we will consider the case of a high quality protein that is extensively digested. In this case, then about 25% of dietary protein is potentially available for incorporation into protein [37]. This assumption is based on the long-standing knowledge that nitrogen retention is about 20-25% of ingested protein over a wide range of protein intake [37]. Thus, it would require approximately 2.6 g/kg/meal to achieve the maximal anabolic response at one meal. The value would be considerably higher with a lower quality protein. For a 70 kg individual it would therefore require 2.6 g/kg/meal * 70 kg = 182 g protein to achieve the maximal anabolic response. This amount of dietary protein considerably exceeds the amount of protein that would normally be eaten in a meal (10-60 g, [2]). Even if our estimates have exaggerated the actual amount of dietary protein needed to elicit maximal response by 100%, it is still highly unlikely that much protein consumption would occur in a single meal. Furthermore, it is possible that we have minimized, rather that exaggerated, the estimate of the maximal anabolic response. We assumed that the anabolic response lasts for 3 h, but with increasingly larger protein meals the time required for net protein synthesis to return to the baseline is likely to be prolonged beyond 3 h, thereby yielding an even greater anabolic response than we estimated."
"Our conclusion from the calculation of the maximal anabolic response is that there is no practical limit to the response to a single meal of protein alone or in a mixed meal. This conclusion is consistent with available data in the literature. It has been recognized for more than 50 years that nitrogen balance increases linearly with increasing amounts of protein intake, even at rates of intake well beyond dietary requirements for protein [37]. Further, net protein balance increases linearly in relation to increasing amounts of dietary protein or amino acid intake when determined either by whole body protein kinetics or measurement of MPS and MPB [38]. Furthermore, it has been shown in an 8-week chronic study that LBM was increased linearly with increasing amount of protein intake encompassing 50-320 g/day (0.72-4.2☠︎ g/kg/day) in young subjects [24]. The upper range of protein intake far exceeded the amount of protein that is known to stimulate a maximal MPS. This finding, in conjunction with findings from our previous studies [18,19], supports our conclusion."
"The theoretical maximal anabolic response of 2.6 g/kg/meal far surpasses the value of 0.24 g (for young adults) or 0.4 g (for older adults) dietary protein/kg/meal for MPS determined in response to varying doses of whey protein isolate or egg protein [25]. There are several possible explanations for the large difference between the amount of high-quality protein needed to maximally stimulate MPS and the total anabolic response. First, the values of protein intake (i.e., 0.24 and 0.4 g/kg/meal for young and older adults, respectively) for maximizing MPS were determined in response to the intake of pure protein, whereas the maximal values in our calculations assumed the dietary protein was contained in a mixed meal that elicited an insulin response and potentially a rise in intracellular amino acids due to hyperaminoacidemia, with the associated suppression of breakdown. Second, we assumed that both the maximal synthetic effect as well as the maximal inhibition of breakdown at the whole body level could be achieved simultaneously in response to a single meal, and this may never occur in practice. On the other hand, our own study showed simultaneously significant and dose-dependent increases in whole body protein synthesis and suppression of breakdown in response to mixed meals with varying amounts of protein [18,19]. Third, while net gain in muscle protein is a primary fate of dietary protein, other tissues and organs respond to dietary protein as well, and the values mentioned above were determined for muscle only. This is a significant factor, as we showed that the whole body anabolic response exceeds the magnitude of the MPS response [18,19]. Finally, and probably most importantly, reliance on MPS excludes the contribution of the suppressive effect of protein breakdown. Our example shown above demonstrates that the potential gain in net muscle protein as a result of suppression of protein breakdown is at least as great as the potential gain as a consequence of stimulation of protein synthesis."
"There was a reasonable rationale for relying on MPS as the sole criterion to determine the maximal anabolic response. Whereas the whole body is potentially involved in the anabolic response to protein ingestion, gain in muscle protein is the most relevant physiological response. Further, at lower levels of protein intake, protein breakdown is not affected as MPS is stimulated [39]. It also may be that the physiological impact of a gain in muscle mass due to stimulation of protein synthesis is greater than when the gain results from a suppression of breakdown. A stimulation of MPS may promote muscle remodeling and improved single muscle fiber function [40]. Muscle protein FSR, normalized for differences in muscle mass, is directly associated with increase strength [8] and function [3]. For example, athletic training generally results in an increase in muscle protein FSR (e.g., Ref. [39]). In contrast, no such remodeling of muscle would be anticipated as a consequence of a suppression of protein breakdown, even if muscle mass increased. Nonetheless, it is clear that assessment of the true anabolic response in terms of muscle mass must include either the measurement of protein synthesis and breakdown, or some other direct measure of muscle mass [1]."
"There is a theoretical upper limit to the anabolic response to dietary protein intake that is dictated by the maximal extent to which protein synthesis can be stimulated and protein breakdown can be suppressed. For the reasons discussed above, we will consider the whole body responses of protein synthesis and breakdown as the best reflection of the total anabolic response to dietary protein. We can make a reasonable estimate of the maximal whole body anabolic response from data in the literature. In our recent acute metabolic study, we observed that in the fasting state whole body protein synthesis was approximately 3.5 g/kg/day, and protein breakdown was approximately 4.3 g/kg/day although not shown explicitly in the paper [19]. Although it is well documented that the maximal increase in MPS in response to consumption of pure dietary protein or amino acids is approximately ~100% greater than the basal value [26-28], similar data are not available for whole body protein synthesis. Similarly, protein dose-response data for the response of MPS to a mixed meal containing protein are not available. Consequently, there is a degree of uncertainty regarding an assumed maximal stimulation of whole body protein synthesis. We will make the conservative estimate that the maximal percent increase in whole body protein synthesis is half as great as the response of MPS, or 50% greater than the basal value. This assumption is based on the fact that muscle is the primary target of dietary protein [4], and therefore muscle is more responsive to variations in intake than other tissues and organs. In our example, a 50% increase in whole body protein synthesis would be 3.5 g/kg/day * 0.50, or 1.75 g/kg/day. With regard to the maximal suppression of breakdown, we have previously shown that intake of a mixed meal containing protein suppressed breakdown by approximately 60% [19], and breakdown cannot be totally shut off, so we can be reasonably confident that whole body protein breakdown can be maximally suppressed to 20% of its basal value (80% suppression). This corresponds to a reduction in breakdown of 3.44 g/kg/day. When the maximal rate of suppression of breakdown (3.44 g/kg/day) is added to the maximal increase in synthesis (1.75 g/kg/day), the total maximal anabolic response is 5.19 g/kg/ day, or 216 mg/kg/h."
"However, the maximal response is not sustained for an entire day in response to a single meal. If we make the conservative assumption that the response to a single meal containing a large amount of protein to elicit the maximal anabolic response lasts for 3 h, then we calculate that the theoretical total anabolic response is approximately 3 h/meal * 216 mg/kg/h = 648 mg/kg/meal."
It would make sense to exclude the sleeping period and divide by meals, but it would make it more absurd and whole-prey eating can take days to digest, it's like casein at night.
- Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Training
- Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Training
"The amount of protein intake required to stimulate the maximal anabolic response depends on the quality of the protein, where quality is defined by the amount and profile of EAAs, as well as the true ileal digestibility of the protein [17,36]. For the purpose of this example, we will consider the case of a high quality protein that is extensively digested. In this case, then about 25% of dietary protein is potentially available for incorporation into protein [37]. This assumption is based on the long-standing knowledge that nitrogen retention is about 20-25% of ingested protein over a wide range of protein intake [37]. Thus, it would require approximately 2.6 g/kg/meal to achieve the maximal anabolic response at one meal. The value would be considerably higher with a lower quality protein. For a 70 kg individual it would therefore require 2.6 g/kg/meal * 70 kg = 182 g protein to achieve the maximal anabolic response. This amount of dietary protein considerably exceeds the amount of protein that would normally be eaten in a meal (10-60 g, [2]). Even if our estimates have exaggerated the actual amount of dietary protein needed to elicit maximal response by 100%, it is still highly unlikely that much protein consumption would occur in a single meal. Furthermore, it is possible that we have minimized, rather that exaggerated, the estimate of the maximal anabolic response. We assumed that the anabolic response lasts for 3 h, but with increasingly larger protein meals the time required for net protein synthesis to return to the baseline is likely to be prolonged beyond 3 h, thereby yielding an even greater anabolic response than we estimated."
"Our conclusion from the calculation of the maximal anabolic response is that there is no practical limit to the response to a single meal of protein alone or in a mixed meal. This conclusion is consistent with available data in the literature. It has been recognized for more than 50 years that nitrogen balance increases linearly with increasing amounts of protein intake, even at rates of intake well beyond dietary requirements for protein [37]. Further, net protein balance increases linearly in relation to increasing amounts of dietary protein or amino acid intake when determined either by whole body protein kinetics or measurement of MPS and MPB [38]. Furthermore, it has been shown in an 8-week chronic study that LBM was increased linearly with increasing amount of protein intake encompassing 50-320 g/day (0.72-4.2☠︎ g/kg/day) in young subjects [24]. The upper range of protein intake far exceeded the amount of protein that is known to stimulate a maximal MPS. This finding, in conjunction with findings from our previous studies [18,19], supports our conclusion."
"The theoretical maximal anabolic response of 2.6 g/kg/meal far surpasses the value of 0.24 g (for young adults) or 0.4 g (for older adults) dietary protein/kg/meal for MPS determined in response to varying doses of whey protein isolate or egg protein [25]. There are several possible explanations for the large difference between the amount of high-quality protein needed to maximally stimulate MPS and the total anabolic response. First, the values of protein intake (i.e., 0.24 and 0.4 g/kg/meal for young and older adults, respectively) for maximizing MPS were determined in response to the intake of pure protein, whereas the maximal values in our calculations assumed the dietary protein was contained in a mixed meal that elicited an insulin response and potentially a rise in intracellular amino acids due to hyperaminoacidemia, with the associated suppression of breakdown. Second, we assumed that both the maximal synthetic effect as well as the maximal inhibition of breakdown at the whole body level could be achieved simultaneously in response to a single meal, and this may never occur in practice. On the other hand, our own study showed simultaneously significant and dose-dependent increases in whole body protein synthesis and suppression of breakdown in response to mixed meals with varying amounts of protein [18,19]. Third, while net gain in muscle protein is a primary fate of dietary protein, other tissues and organs respond to dietary protein as well, and the values mentioned above were determined for muscle only. This is a significant factor, as we showed that the whole body anabolic response exceeds the magnitude of the MPS response [18,19]. Finally, and probably most importantly, reliance on MPS excludes the contribution of the suppressive effect of protein breakdown. Our example shown above demonstrates that the potential gain in net muscle protein as a result of suppression of protein breakdown is at least as great as the potential gain as a consequence of stimulation of protein synthesis."
"There was a reasonable rationale for relying on MPS as the sole criterion to determine the maximal anabolic response. Whereas the whole body is potentially involved in the anabolic response to protein ingestion, gain in muscle protein is the most relevant physiological response. Further, at lower levels of protein intake, protein breakdown is not affected as MPS is stimulated [39]. It also may be that the physiological impact of a gain in muscle mass due to stimulation of protein synthesis is greater than when the gain results from a suppression of breakdown. A stimulation of MPS may promote muscle remodeling and improved single muscle fiber function [40]. Muscle protein FSR, normalized for differences in muscle mass, is directly associated with increase strength [8] and function [3]. For example, athletic training generally results in an increase in muscle protein FSR (e.g., Ref. [39]). In contrast, no such remodeling of muscle would be anticipated as a consequence of a suppression of protein breakdown, even if muscle mass increased. Nonetheless, it is clear that assessment of the true anabolic response in terms of muscle mass must include either the measurement of protein synthesis and breakdown, or some other direct measure of muscle mass [1]."
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