Higher Diet Protein Levels & Safety
iPB Protein Bite
It is still common today to come across internet and magazine articles, social media posts and even some professional commentary that either directly states or suggests that protein intakes above the current base requirement levels stated by many countries/organizations as presenting a risk to the function and health of various tissue such as the kidneys, liver and bone. However, the potential adverse effect of higher protein intakes on human health generally unfounded and in contrast to the most current evidence-based understanding of the issue. While the misinformation on this matter continues, an opportunity also exists for confusion regarding scenarios where protein requirements are clearly elevated above RDA levels and alike globally, such as aging and caloric restriction. Furthermore, it creates confusion when evaluating certain dietary recommendations such as the Adequate Macronutrient Distribution Range (AMDR) in the United States and Canada which states a protein range spanning 10-35% of energy intake with the upper end of the range dramatically raising protein intake above requirement standards. Thus, a need exists for a clearer understanding of this issue so that professionals, media and consumers are well informed with the most up-to-date information.
2018 iPB Consensus Statement on Higher Diet Protein Levels and Safety
Based on the most up-to-date research and understanding of the issue, the International Protein Board presents its 2018 Consensus Statement on Protein Safety with intakes greater than requirements:
"In general, higher protein intakes and as much as double 'reference requirement standards' stated by many countries(e.g. 0.8g/kg BW) would not pose a risk for adverse renal, liver and bone function or integrity in otherwise healthy adults."
International Protein Board 2018 Survey results on Higher Protein Intake and Safety:
iPB Survey 2018
Higher Protein Levels & Safety
iPB SURVEY QUESTION: "Protein intakes as high as two times the RDA (1.6g/kg or 92g for women and 112g for men) pose a serious kidney, liver and/or bone risk for otherwise generally healthy adults"
iPB ANSWER SCORE: The iPB survey score is 4.73 with answers range from 1 = Strongly Agree to 5 = Strongly Disagree.
2018 iPB Brief
Higher Diet Protein Levels and Safety
As a macronutrient, protein is unique from carbohydrate and fat in that its building block amino acids contain nitrogen. Thus, when amino acids are broken down for energy or other purposes, the nitrogen is largely removed from the body in the form of urea, which is produced in the liver and voided in the urine.1 Moreover, as dietary protein intake increases the work of the liver to produce more urea, as well as the work of the kidneys to filter and excrete it, a lesser amount of additional nitrogen-based waste substances increases in relative fashion as often reflected in augmented glomerular filtration rate (eGFR).2-5 Based on these basic and adaptive physiological responses, some have concluded that these scenarios could overwork these organs and eventually lead to aberrations in function and damage.2
Without question, for those individuals presenting compromised renal function, higher protein intakes can indeed be problematic.2,6 However, on the contrary, researchers have reported that higher protein intakes may lead to adaptations that increase the efficiency of urea excretion and do not alter markers of damage or dysfunction of the liver or kidneys.7-12 For instance, in one review of this topic, researchers set the level of “high protein diets” at a threshold level ≥1.5g/kg body weight or approximately twice the RDA in the U.S.7 Moreover, much of the research with higher protein intakes alone have not shown that protein by itself increases blood risk factors associated with liver dysfunction and/or heart disease.10-12
Meanwhile, higher levels of dietary protein have been purported to potentially increase the rate of bone loss and in turn increase the risk of osteoporosis. Much of this position is based on the results of studies that reported that higher protein intakes were associated with increased urinary calcium.13 Moreover, additional research suggested that since calcium absorption was not increased concomitant to increased dietary protein, the urinary calcium was derived from bone.14-16 This in turn led some to hunt for a mechanism and supporting the idea that higher protein intake and in particular sulfur-containing amino acids, would increase the acidity of the blood (e.g. acid diet) which in turn dissolves more bone. Since bone mineral complexes, calcium phosphate and hydroxyapatite, are calcium based, the liberated calcium would enter circulation and in turn be filtered by the kidneys and voided in urine.
Despite the seemingly easy connection in potential mechanism and outcome, current research does not support the connection nor the concern. Also, some follow up investigations suggest that while protein intake may indeed increase urinary loss of calcium, it is more of a reflection of increased absorption of food derived calcium and leaving bone unaffected.17-20 Furthermore, the results of three meta-analysis studies, have reported either no impact or potential improvement on hip fractures.21,22 In support, in another meta-analysis led by the National Osteoporosis Foundation (NOF) recently reviewed the relationship between protein intake and bone density and found either no detrimental impact with higher protein intake or a potential benefit to certain parts of the skeleton.23
The relationship between protein and bone is an interesting one. Protein makes up to 50% of bone volume and approximately one-third of its mass.1,23 It provides the structural matrix of bone, whereas calcium is the dominant mineral within that matrix. Collagen and other proteins form the organic matrix of bone.1,24 Based on this anatomical aspect, an adequate dietary protein intake would seem be an important and positive factor in the development and maintenance of adult bone mass. In support, a recent review of pertinent research reported a positive relationship between dietary protein and skeletal development in children and adolescents.25
All-in-all there does not seem need for concern of adverse effects of protein intakes significantly higher than the requirement standards set by many countries. In fact, higher protein intakes may even be beneficial to bone health. In the U.S. for instance, the Institutes of Medicine (IOM), which sets the Dietary Reference Intakes (DRI) including the RDA, concluded that there was not sufficient evidence to set an upper limit for protein, but did include the AMDR of 10-35% of total energy for protein intake.26
- Medeiros DM & Wildman REC. Protein & Amino Acids, In: Advanced Human Nutrition. Jones & Bartlett 2018.
- King AJ, Levey AS. Dietary protein and renal function. J Am Soc Nephrol. 1993 May;3(11):1723-37. (Access the Study – Open Access)
- Cirillo M, Zingone F, Lombardi C, Cavallo P, Zanchetti A, & Bilancio G (2015). Population-based dose–response curve of glomerular filtration rate to dietary protein intake. Nephrology Dialysis Transplantation,30(7), 1156-1162. (Access the Study – Open Access)
- Cirillo M, Lombardi C, Chiricone D, Santo N G, Zanchetti A, & Bilancio G (2014). Protein intake and kidney function in the middle-age population: contrast between cross-sectional and longitudinal data. Nephrology Dialysis Transplantation,29(9), 1733-1740. (Access the Study – Open Access)
- Bilo HJ, Schaap GH, Blaak E, Gans RO, Oe PL, Donker AJ. Effects of chronic and acute protein administration on renal function in patients with chronic renal insufficiency. Nephron. 1989;53(3):181-7.
- Brenner BM, Meyer TW, Hostetter TH. Dietary protein intake and the progressive nature of kidney disease: the role of hemodynamically mediated glomerular injury in the pathogenesis of progressive glomerular sclerosis in aging, renal ablation, and intrinsic renal disease. N Engl J Med. 1982 Sep 9;307(11):652-9.
- Martin W, Armstrong L, & Rodriguez N (2013). Dietary Protein Intake and Renal Function. Clinical Nutrition,121-140. (Access the Study – Open Access)
- Berryman C E, Agarwal S, Lieberman H R, Fulgoni V L, & Pasiakos S M (2016). Diets higher in animal and plant protein are associated with lower adiposity and do not impair kidney function in US adults. The American Journal of Clinical Nutrition,104(3), 743-749. (Access the Study – Open Access)
- Moller G, Andersen J R, Ritz C, Silvestre M P, Navas-Carretero S, Jalo E, Christensen P, Simpson E, Taylor M, Martinez J A, Macdonald I, Swindell N, Mackintosh K A, Stratton G, Fogelholm M, Larsen T M, Poppitt S D, Dragsted L O, and Raben A (2018). Higher Protein Intake Is Not Associated with Decreased Kidney Function in Pre-Diabetic Older Adults Following a One-Year Intervention—A Preview Sub-Study. Nutrients,10(1), 54. (Access the Study – Open Access)
- Antonio J, Ellerbroek A, Silver T, Vargas L, Tamayo A, Buehn R, & Peacock C A (2016). A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males. Journal of Nutrition and Metabolism,2016, 1-5. (Access the Study- Open Access)
- Antonio J, & Ellerbroek A. (2018). Case Reports on Well-Trained Bodybuilders: Two Years on a High Protein Diet. Journal of Exercise physiology,21(1), 14-24. (Access the Study – Open Access)
- Antonio J, Ellerbroek A, Silver T, Vargas L, Peacock C. The effects of a high protein diet on indices of health and body composition--a crossover trial in resistance-trained men. J Int Soc Sports Nutr. 2016 Jan 16;13:3. (Access the Study – Open Access)
- Kerstettler JE, Allen LH. Protein intake and calcium homeostasis. Adv Nutr Res. 1994;9:167-81.
- Hegsted M, Linkswiler HM Long-term effects of level of protein intake on calcium metabolism in young adult women. J Nutr. 1981 Feb;111(2):244-51.
- Schuette SA, Hegsted M, Zemel MB, Linkswiler HM. Renal acid, urinary cyclic AMP, and hydroxyproline excretion as affected by level of protein, sulfur amino acid, and phosphorus intake. J Nutr. 1981 Dec;111(12):2106-16.
- Schuette SA, Zemel MB, Linkswiler HM. Studies on the mechanism of protein-induced hypercalciuria in older men and women. J Nutr. 1980 Feb;110(2):305-15.
- Surdykowski AK, Kenny AM, Insogna KL, Kerstetter JE. Optimizing bone health in older adults: the importance of dietary protein Aging health. Aging health. 2010 Jun 1; 6(3): 345–357. (Access the Study – Open Access)
- Kerstetter JE, O’Brian KO, Caseria DM, Wall DE, Insogna KL. The impact of dietary protein on calcium absorption and kinetic measure of bone turnover in women. J Clin Endocrinol Metab 2005; 90: 26-31.
- Hunt JR, Johnson LK, Fariba Roughead ZK. Dietary protein and calcium interact to influence calcium retention: a controlled feeding study. Am J Clin Nutr. 2009 May;89(5):1357-65. (Access the Study – Open Access)
- Roughead ZK, Johnson LK, Lykken GI, Hunt JR. Controlled high meat diets do not affect calcium retention or indices of bone status in healthy postmenopausal women. J Nutr. 2003 Apr;133(4):1020-6.
- Darling AL, Millward DJ, Torgerson DJ, Hewitt CE, Lanham-New SA. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr. 2009 Dec;90(6):1674-92.
- Wu AM, Sun XL, Lv QB, Zhou Y, Xia DD, Xu HZ, Huang QS, Chi YL.The relationship between dietary protein consumption and risk of fracture: a subgroup and dose-response meta-analysis of prospective cohort studies. Sci Rep. 2015 Mar 16;5:9151. (Access the Study – Open Access)
- Shams-White MM, Chung M, Du M, Fu Z, Insogna KL, Karlsen MC, LeBoff MS, Shapses SA, Sackey J, Wallace TC, Weaver CM. Dietary protein and bone health: a systematic review and meta-analysis from the National Osteoporosis Foundation. Am J Clin Nutr 2017;105:1528–43.
- Heaney RP. Effects of protein on the calcium economy. Int Congr Ser 2007;1297:191–7.
- Weaver CM, Gordon CM, Janz KF, Kalkwarf HJ, Lappe JM, Lewis R, O’Karma M, Wallace TC, Zemel BS. The National Osteoporosis Foundation’s position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations. Osteoporos Int 2016;27:1281–386. (Access the Study – Open Access)
- Food and Nutrition Board, Institute of Medicine: Macronutrient and Healthful Diets. In Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) Washington, D.C. The National Academies Press; 2002: 609-696.
Dr Robert Wildman overviews the potential for higher protein intakes to negatively influence the function and health - Dr Rob Link
Dr. Jose Antonio: High protein Diets - https://www.youtube.com/watch?v=BZpYH3HegiI
Dr. Jose Antonio, PhD talks the benefits of “protein over-feeding” https://www.youtube.com/watch?v=wDgtJ--a1ek