A low-protein diet is a diet in which people reduce their intake of protein. A low-protein diet is prescribed for those with inherited metabolic disorders, such as Phenylketonuria and Homocystinuria and reduced protein levels have been used by people with kidney or liver disease. Low protein consumption appears to reduce the risk of bone breakage, presumably through changes in calcium homeostasis. Consequently, there is no uniform definition of what constitutes low-protein, because the amount and composition of protein for an individual suffering from phenylketonuria would differ substantially from one suffering homocystinuria or tyrosinemia. The amount used by those with liver disease would still result in individuals being in nitrogen balance.
Amino acids that are excess to requirement cannot be stored, but must be modified by deamination (removal of the amine group). As this occurs in the liver and kidneys, some individuals with damaged livers or kidneys may be advised to eat less protein. Due to the sulphur content of the amino acids methionine and cysteine, excess of these amino acids leads to the production of acid through sulphate ions. These sulphate ions may be neutralized by calcium ions from bone, which may lead to net urinary loss of calcium. This might lead to reduction in bone mineral density over time. Individuals suffering from phenylketonuria lack the enzyme to convert phenylalanine to tyrosine so low levels of this amino acid need to be provided in the diet. Homocystinuria is an inherited disorder involving the metabolism of the amino acid methionine leading to the accumulation of homocysteine. Treatment includes providing low levels of methionine and high levels of vitamin B6 in the diet.
Low-protein diets are in vogue among some members of the general public because of the impact of protein intake on Insulin/Insulin-like growth factor 1 Signalling (IIS) and the direct sensing of amino acid availability by mammalian target of rapamycin (mTOR), two systems that are implicated in longevity and cancer proliferation. Apart from low protein intake, such as in the 80:10:10 diet, other attempts to modulate IIS are through intermittent fasting and the 5:2 diet.
By studying the composition of food in the local population in Germany, Carl von Voit established a standard of 118 grams of protein per day. Russell Henry Chittenden showed that less than half that amount was needed to maintain good health. Horace Fletcher was an early populariser of low-protein diets, which he advocated along with chewing.
The daily requirement for humans to remain in nitrogen balance is relatively small. The median human adult requirement for good quality protein is approximately 0.65 gram per kilogram body weight per day and the 97.5 percentile is 0.83 grams per kilogram body weight per day. Children require more protein, depending on the growth phase. A 70 kg adult human who was in the middle of the range would require approximately 45 grams of protein per day to be in nitrogen balance. This would represent less than 10% of kilocalories in a notional 2,200 kilocalorie ration. William Cumming Rose and his team studied the essential amino acids, helping to define minimum amounts needed for normal health. For adults, the recommended minimum amounts of each essential amino acid varies from 4 to 39 milligrams per kilogram of body weight per day. To be of good quality, protein only needs to come from a wide variety of foods; there is neither a need to mix animal and plant food together nor a need to complement specific plant foods, such as rice and beans. The notion that such specific combinations of plant protein need to be made to give good quality protein stems from the book Diet for a Small Planet. Plant protein is often described as incomplete, suggesting that they lack one or more of the essential amino acids. Apart from rare examples, such as Taro, each plant provides an amount of all the essential amino acids. However, the relative abundance of the essential amino acids is more variable in plants than that found in animals, which tend to be very similar in essential amino acid abundance, and this has led to the misconception that plant proteins are deficient in some way.
Low-protein vs calorie restriction
Calorie restriction has been demonstrated to increase the life span and decrease the age-associated morbidity of many experimental animals. Increases in longevity or reductions in age-associated morbidity have also been shown for model systems where protein or specific amino acids have been reduced. In particular, experiments in model systems in rats, mice, and Drosophila fruit flies have shown increases in life-span with reduced protein intake comparable to that for calorie restriction. Restriction of the amino acid methionine, which is required to initiate protein synthesis, is sufficient to extend lifespan.
Some of the most dramatic effects of Calorie restriction are on metabolic health, promoting leanness, decreasing blood sugar and increasing insulin sensitivity. Low-protein diets mimic many of the effects of Calorie restriction but may engage different metabolic mechanisms. Low protein diets rapidly reduce fat and restores normal insulin sensitivity to diet-induced obese mice. Specifically restricting consumption of the three branched-chain amino acids leucine, isoleucine and valine is sufficient to promote leanness and improve regulation of blood glucose.
The diets of humans living in some of the Blue Zones, regions of enhanced numbers of centenarians and reduced age-associated morbidity, contain less than 10% of energy from protein, although reports on all the Blue Zones are not available. None of the diets in these regions is completely based on plants, but plants form the bulk of the food eaten. Although it has been speculated that some of these populations are under calorie restriction, this is contentious as their smaller size is consistent with the lower food consumption.
Low-protein and liver disease
In the past a standard dietary treatment for those suffering from liver disease or damage was a low protein, high carbohydrate, moderate fat and low salt diet. However, more recent research suggests that a high protein diet is required of 1.2–2 g of protein per kg.[clarification needed] Levels of up to 2 g/kg body weight/day have been demonstrated to not worsen encephalopathy. In addition, vitamin supplements especially vitamin B group should be taken. Sodium might have to be restricted to 500–1500 mg per day.
Low-protein and kidney disease
Low-protein diets to treat kidney disease include the Rice diet, which was started by Walter Kempner at Duke University in 1939. This diet was a daily ration of 2,000 Calories consisting of moderate amounts of boiled rice, sucrose and dextrose, and a restricted range of fruit, supplemented with vitamins. Sodium and chloride were restricted to 150 mg and 200 mg respectively. It showed remarkable effects on control of edema and hypertension. Although the Rice diet was designed to treat kidney and vascular disease, the large weight loss associated with the diet led to a vogue in its use for weight loss which lasted for more than 70 years. The Rice Diet program closed in 2013. Other low-protein starch-based diets like John A. McDougall's program continue to be offered for kidney disease and hypertension.
Low-protein and osteoporosis
The effect of protein on osteoporosis and risk of bone fracture is complex. Calcium loss from bone occurs at protein intake below requirement when individuals are in negative protein balance, suggesting that too little protein is dangerous for bone health. IGF-1, which contributes to muscle growth, also contributes to bone growth, and IGF-1 is modulated by protein intake. However, at high protein levels, a net loss of calcium may occur through the urine in neutralizing the acid formed from the deamination and subsequent metabolism of methionine and cysteine. Large prospective cohort studies have shown a slight increase in risk of bone fracture when the quintile of highest protein consumption is compared to the quintile of lowest protein consumption. In these studies, the trend is also seen for animal protein but not plant protein, but the individuals differ substantially in animal protein intake and very little in plant protein intake. As protein consumption increases, calcium uptake from the gut is enhanced. Normal increases in calcium uptake occur with increased protein in the range 0.8 grams to 1.5 grams of protein per kilogram body weight per day. However, calcium uptake from the gut does not compensate for calcium loss in the urine at protein consumption of 2 grams of protein per kilogram of body weight. Calcium is not the only ion that neutralizes the sulphate from protein metabolism, and overall buffering and renal acid load also includes anions such as bicarbonate, organic ions, phosphorus and chloride as well as cations such as ammonium, titrateable acid, magnesium, potassium and sodium. The study of Potential Renal Acid Load (PRAL) suggests that increased consumption of fruits, vegetables and cooked legumes increases the ability of the body to buffer acid from protein metabolism, because they contribute to a base forming potential in the body due to their relative concentrations of proteins and ions. However, not all plant material is base forming, for example, nuts, grains and grain products add to the acid load.
In the United Kingdom, low-protein products and substitutes are prescribed through the health service.
Low protein, vegetarian diets have been hypothesized to be linked to longer life.
- Feskanich, Diane; Willett, Walter C.; Stampfer, Meir J.; Colditz, Graham A. (1996). "Protein Consumption and Bone Fractures in Women". American Journal of Epidemiology. 143 (5): 472–9. doi:10.1093/oxfordjournals.aje.a008767. PMID 8610662.
- Zea-Rey, Alexandra V.; Cruz-Camino, Héctor; Vazquez-Cantu, Diana L.; Gutiérrez-García, Valeria M.; Santos-Guzmán, Jesús; Cantú-Reyna, Consuelo (27 November 2017). "The Incidence of Transient Neonatal Tyrosinemia Within a Mexican Population" (PDF). Journal of Inborn Errors of Metabolism and Screening. 5: 232640981774423. doi:10.1177/2326409817744230.
- Alayev, Anya; Holz, Marina K. (2013). "mTOR signaling for biological control and cancer". Journal of Cellular Physiology. 228 (8): 1658–64. doi:10.1002/jcp.24351. PMC 4491917. PMID 23460185.
- Jewell, Jenna L.; Guan, Kun-Liang (2013). "Nutrient signaling to mTOR and cell growth". Trends in Biochemical Sciences. 38 (5): 233–42. doi:10.1016/j.tibs.2013.01.004. PMC 3634910. PMID 23465396.
- Pollak, Michael N.; Schernhammer, Eva S.; Hankinson, Susan E. (2004). "Insulin-like growth factors and neoplasia". Nature Reviews Cancer. 4 (7): 505–18. doi:10.1038/nrc1387. PMID 15229476.
- Thissen, Jean-Paul; Ketelslegers, Jean-Marie; Underwood, Louis E. (1994). "Nutritional Regulation of the Insulin-Like Growth Factors". Endocrine Reviews. 15 (1): 80–101. doi:10.1210/edrv-15-1-80. PMID 8156941.
- Lewis, Howard B. (1944). "Russell Henry Chittenden (1856–1943)". Journal of Biological Chemistry. 153 (2): 339–42.
- Rand, William M; Pellett, Peter L; Young, Vernon R (2003). "Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults". The American Journal of Clinical Nutrition. 77 (1): 109–27. doi:10.1093/ajcn/77.1.109. PMID 12499330.
- McDougall, J. (2002). "Plant Foods Have a Complete Amino Acid Composition". Circulation. 105 (25): e197, author reply e197. doi:10.1161/01.CIR.0000018905.97677.1F. PMID 12082008.
- http://nutritiondata.self.com/[full citation needed]
- Ooka, Hiroshi; Segall, Paul E.; Timiras, Paola S. (1988). "Histology and survival in age-delayed low-tryptophan-fed rats". Mechanisms of Ageing and Development. 43 (1): 79–98. doi:10.1016/0047-6374(88)90099-1. PMID 3374178.
- Orentreich, Norman; Matias, Jonathan R.; DeFelice, Anthony; Zimmerman, Jay A. (1993). "Low Methionine Ingestion by Rats Extends Life Span". The Journal of Nutrition. 123 (2): 269–74. doi:10.1093/jn/123.2.269 (inactive 2019-08-20). PMID 8429371.
- Miller, Richard A.; Buehner, Gretchen; Chang, Yayi; Harper, James M.; Sigler, Robert; Smith-Wheelock, Michael (2005). "Methionine-deficient diet extends mouse lifespan, slows immune and lens aging, alters glucose, T4, IGF-I and insulin levels, and increases hepatocyte MIF levels and stress resistance". Aging Cell. 4 (3): 119–25. doi:10.1111/j.1474-9726.2005.00152.x. PMID 15924568.
- Grandison, Richard C.; Piper, Matthew D. W.; Partridge, Linda (2009). "Amino-acid imbalance explains extension of lifespan by dietary restriction in Drosophila". Nature. 462 (7276): 1061–4. doi:10.1038/nature08619. PMC 2798000. PMID 19956092.
- Caro, Pilar; Gomez, Jose; Sanchez, Ines; Naudi, Alba; Ayala, Victoria; López-Torres, Monica; Pamplona, Reinald; Barja, Gustavo (2009). "Forty Percent Methionine Restriction Decreases Mitochondrial Oxygen Radical Production and Leak at Complex I During Forward Electron Flow and Lowers Oxidative Damage to Proteins and Mitochondrial DNA in Rat Kidney and Brain Mitochondria". Rejuvenation Research. 12 (6): 421–34. doi:10.1089/rej.2009.0902. PMID 20041736.
- Brind, Joel; Malloy, Virginia; Augie, Ines; Caliendo, Nicholas; Vogelman, Joseph H; Zimmerman, Jay A.; Orentreich, Norman (2011). "Dietary glycine supplementation mimics lifespan extension by dietary methionine restriction in Fisher 344 rats". The FASEB Journal. 25 (Meeting Abstract Supplement): 528.2. doi:10.1096/fasebj.25.1_supplement.528.2 (inactive 2019-08-20).
- Fontana, Luigi; Partridge, Linda (2015-03-26). "Promoting health and longevity through diet: from model organisms to humans". Cell. 161 (1): 106–118. doi:10.1016/j.cell.2015.02.020. ISSN 1097-4172. PMC 4547605. PMID 25815989.
- Solon-Biet, Samantha M.; Mitchell, Sarah J.; Coogan, Sean C. P.; Cogger, Victoria C.; Gokarn, Rahul; McMahon, Aisling C.; Raubenheimer, David; de Cabo, Rafael; Simpson, Stephen J. (2015-06-16). "Dietary Protein to Carbohydrate Ratio and Caloric Restriction: Comparing Metabolic Outcomes in Mice". Cell Reports. 11 (10): 1529–1534. doi:10.1016/j.celrep.2015.05.007. ISSN 2211-1247. PMC 4472496. PMID 26027933.
- Cummings, Nicole E.; Williams, Elizabeth M.; Kasza, Ildiko; Konon, Elizabeth N.; Schaid, Michael D.; Schmidt, Brian A.; Poudel, Chetan; Sherman, Dawn S.; Yu, Deyang (2017-12-19). "Restoration of metabolic health by decreased consumption of branched-chain amino acids". The Journal of Physiology. 596 (4): 623–645. doi:10.1113/JP275075. ISSN 1469-7793. PMC 5813603. PMID 29266268.
- Fontana, Luigi; Cummings, Nicole E.; Arriola Apelo, Sebastian I.; Neuman, Joshua C.; Kasza, Ildiko; Schmidt, Brian A.; Cava, Edda; Spelta, Francesco; Tosti, Valeria (2016-06-21). "Decreased Consumption of Branched-Chain Amino Acids Improves Metabolic Health". Cell Reports. 16 (2): 520–30. doi:10.1016/j.celrep.2016.05.092. ISSN 2211-1247. PMC 4947548. PMID 27346343.
- Willcox, B. J.; Willcox, D. C.; Todoriki, H.; Fujiyoshi, A.; Yano, K.; He, Q.; Curb, J. D.; Suzuki, M. (2007). "Caloric Restriction, the Traditional Okinawan Diet, and Healthy Aging: The Diet of the World's Longest-Lived People and Its Potential Impact on Morbidity and Life Span". Annals of the New York Academy of Sciences. 1114: 434–55. doi:10.1196/annals.1396.037. PMID 17986602.
- Pes, G.M.; Tolu, F.; Poulain, M.; Errigo, A.; Masala, S.; Pietrobelli, A.; Battistini, N.C.; Maioli, M. (2013). "Lifestyle and nutrition related to male longevity in Sardinia: An ecological study". Nutrition, Metabolism and Cardiovascular Diseases. 23 (3): 212–9. doi:10.1016/j.numecd.2011.05.004. PMID 21958760.
- Keys, Ancel; Kimura, Noboru (1970). "Diets of Middle-Aged Farmers in Japan". The American Journal of Clinical Nutrition. 23 (2): 212–23. doi:10.1093/ajcn/23.2.212. PMID 5415568.
- MedlinePlus Encyclopedia Diet - liver disease
- Plauth, M.; Cabré, E.; Riggio, O.; Assis-Camilo, M.; Pirlich, M.; Kondrup, J.; Ferenci, P.; Holm, E.; vom Dahl, S.; Müller, M.J.; Nolte, W. (2006). "ESPEN Guidelines on Enteral Nutrition: Liver disease". Clinical Nutrition. 25 (2): 285–94. doi:10.1016/j.clnu.2006.01.018. PMID 16707194.
- Kempner, Walter (1946). "Some Effects of the Rice Diet Treatment of Kidney Disease and Hypertension". Bulletin of the New York Academy of Medicine. 22 (7): 358–70. PMC 1871537. PMID 19312487.
- Kempner, Walter (1948). "Treatment of hypertensive vascular disease with rice diet". The American Journal of Medicine. 4 (4): 545–77. doi:10.1016/0002-9343(48)90441-0. PMID 18909456.
- "Rice diet shuts down North Carolina home after 70 years". Fox News. Associated Press. September 10, 2013.
- Heaney, Robert P; Layman, Donald K (2008). "Amount and type of protein influences bone health". The American Journal of Clinical Nutrition. 87 (5): 1567S–1570S. doi:10.1093/ajcn/87.5.1567S. PMID 18469289.
- Remer, Thomas; Manz, Friedrich (1995). "Potential Renal Acid Load of Foods and its Influence on Urine pH". Journal of the American Dietetic Association. 95 (7): 791–7. doi:10.1016/S0002-8223(95)00219-7. PMID 7797810.
- Barzel, Uriel S.; Massey, Linda K. (1998). "Excess Dietary Protein Can Adversely Affect Bone". The Journal of Nutrition. 128 (6): 1051–3. doi:10.1093/jn/128.6.1051. PMID 9614169.
- Grandison, Richard C.; Piper, Matthew D. W.; Partridge, Linda (2009). "Amino-acid imbalance explains extension of lifespan by dietary restriction in Drosophila". Nature. 462 (7276): 1061–4. doi:10.1038/nature08619. PMC 2798000. PMID 19956092. Lay summary – NHS Choices (December 3, 2009).