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A review of issues of dietary protein intake in humans.

Abstract

Considerable debate has taken place over the safety and validity of increased protein intakes for both weight control and muscle synthesis. The advice to consume diets high in protein by some health professionals, media and popular diet books is given despite a lack of scientific data on the safety of increasing protein consumption. The key issues are the rate at which the gastrointestinal tract can absorb amino acids from dietary proteins (1.3 to 10 g/h) and the liver's capacity to deaminate proteins and produce urea for excretion of excess nitrogen. The accepted level of protein requirement of 0.8g x kg(-1) x d(-1) is based on structural requirements and ignores the use of protein for energy metabolism. High protein diets on the other hand advocate excessive levels of protein intake on the order of 200 to 400 g/d, which can equate to levels of approximately 5 g x kg(-1) x d(-1), which may exceed the liver's capacity to convert excess nitrogen to urea. Dangers of excessive protein, defined as when protein constitutes > 35% of total energy intake, include hyperaminoacidemia, hyperammonemia, hyperinsulinemia nausea, diarrhea, and even death (the "rabbit starvation syndrome"). The three different measures of defining protein intake, which should be viewed together are: absolute intake (g/d), intake related to body weight (g x kg(-1) x d(-1)) and intake as a fraction of total energy (percent energy). A suggested maximum protein intake based on bodily needs, weight control evidence, and avoiding protein toxicity would be approximately of 25% of energy requirements at approximately 2 to 2.5 g x kg(-1) x d(-1), corresponding to 176 g protein per day for an 80 kg individual on a 12,000kJ/d diet. This is well below the theoretical maximum safe intake range for an 80 kg person (285 to 365 g/d).

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  • Authors+Show Affiliations

    ,

    B Personal Pty Ltd., Melbourne, Victoria 3001, Australia.

    Source

    MeSH

    Amino Acids
    Body Weight
    Dietary Proteins
    Energy Metabolism
    Exercise
    Humans
    Muscle, Skeletal
    Nutritional Requirements
    Safety

    Pub Type(s)

    Journal Article
    Review

    Language

    eng

    PubMed ID

    16779921

    Citation

    Bilsborough, Shane, and Neil Mann. "A Review of Issues of Dietary Protein Intake in Humans." International Journal of Sport Nutrition and Exercise Metabolism, vol. 16, no. 2, 2006, pp. 129-52.
    Bilsborough S, Mann N. A review of issues of dietary protein intake in humans. Int J Sport Nutr Exerc Metab. 2006;16(2):129-52.
    Bilsborough, S., & Mann, N. (2006). A review of issues of dietary protein intake in humans. International Journal of Sport Nutrition and Exercise Metabolism, 16(2), pp. 129-52.
    Bilsborough S, Mann N. A Review of Issues of Dietary Protein Intake in Humans. Int J Sport Nutr Exerc Metab. 2006;16(2):129-52. PubMed PMID: 16779921.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - A review of issues of dietary protein intake in humans. AU - Bilsborough,Shane, AU - Mann,Neil, PY - 2006/6/20/pubmed PY - 2006/8/1/medline PY - 2006/6/20/entrez SP - 129 EP - 52 JF - International journal of sport nutrition and exercise metabolism JO - Int J Sport Nutr Exerc Metab VL - 16 IS - 2 N2 - Considerable debate has taken place over the safety and validity of increased protein intakes for both weight control and muscle synthesis. The advice to consume diets high in protein by some health professionals, media and popular diet books is given despite a lack of scientific data on the safety of increasing protein consumption. The key issues are the rate at which the gastrointestinal tract can absorb amino acids from dietary proteins (1.3 to 10 g/h) and the liver's capacity to deaminate proteins and produce urea for excretion of excess nitrogen. The accepted level of protein requirement of 0.8g x kg(-1) x d(-1) is based on structural requirements and ignores the use of protein for energy metabolism. High protein diets on the other hand advocate excessive levels of protein intake on the order of 200 to 400 g/d, which can equate to levels of approximately 5 g x kg(-1) x d(-1), which may exceed the liver's capacity to convert excess nitrogen to urea. Dangers of excessive protein, defined as when protein constitutes > 35% of total energy intake, include hyperaminoacidemia, hyperammonemia, hyperinsulinemia nausea, diarrhea, and even death (the "rabbit starvation syndrome"). The three different measures of defining protein intake, which should be viewed together are: absolute intake (g/d), intake related to body weight (g x kg(-1) x d(-1)) and intake as a fraction of total energy (percent energy). A suggested maximum protein intake based on bodily needs, weight control evidence, and avoiding protein toxicity would be approximately of 25% of energy requirements at approximately 2 to 2.5 g x kg(-1) x d(-1), corresponding to 176 g protein per day for an 80 kg individual on a 12,000kJ/d diet. This is well below the theoretical maximum safe intake range for an 80 kg person (285 to 365 g/d). SN - 1526-484X UR - https://www.unboundmedicine.com/medline/citation/16779921/full_citation L2 - https://medlineplus.gov/dietaryproteins.html DB - PRIME DP - Unbound Medicine ER -