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Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults

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Background. While high-protein consumption—above the current recommended dietary allowance for adults (RDA: 0.8 g protein/kg body weight/day)—is increasing in popularity, there is a lack of data on its potential adverse effects. Objective. To determine the potential disease risks due to high protein/high meat intake obtained from diet and/or nutritional supplements in humans. Design. Review. Subjects. Healthy adult male and female subjects. Method. In order to identify relevant studies, the electronic databases, Medline and Google Scholar, were searched using the terms:“high protein diet,” “protein overconsumption,” “protein overuse,” and “high meat diet.” Papers not in English were excluded. Further studies were identified by citations in retrieved papers. Results. 32 studies (21 experimental human studies and 11 reviews) were identified. The adverse effects associated with long-term high protein/high meat intake in humans were (a) disorders of bone and calcium homeostasis, (b) disorders of renal function, (c) increased cancer risk, (d) disorders of liver function, and (e) precipitated progression of coronary artery disease. Conclusions. The findings of the present study suggest that there is currently no reasonable scientific basis in the literature to recommend protein consumption above the current RDA (high protein diet) for healthy adults due to its potential disease risks. Further research needs to be carried out in this area, including large randomized controlled trials.
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Hindawi Publishing Corporation
ISRN Nutrition
Volume , Article ID , pages
http://dx.doi.org/.//
Review Article
Adverse Effects Associated with Protein Intake above
the Recommended Dietary Allowance for Adults
Ioannis Delimaris
External Postdoctoral Research Team, Biology Unit, Faculty of Human Sciences, University of essaly, 38221 Volos, Greece
Correspondence should be addressed to Ioannis Delimaris; dr.i.delimaris@gmail.com
Received  May ; Accepted  June 
Academic Editors: F. S. Dioguardi and A. Shaish
Copyright ©  Ioannis Delimaris. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background. While high-protein consumption—above the current recommended dietary allowance for adults (RDA: . g
protein/kg body weight/day)—is increasing in popularity, there is a lack of data on its potential adverse eects. Objective.To
determine the potential disease risks due to high protein/high meat intake obtained from diet and/or nutritional supplements
in humans. Design.Review.Subjects.Healthyadultmaleandfemalesubjects.Method. In order to identify relevant studies, the
electronic databases, Medline and Google Scholar, were searched using the terms:“high protein diet,” “protein overconsumption,
“protein overuse,” and “high meat diet.” Papers not in English were excluded. Further studies were identied by citations in retrieved
papers. Results.  studies ( experimental human studies and  reviews) were identied. e adverse eects associated with long-
term high protein/high meat intake in humans were (a) disorders of bone and calcium homeostasis, (b) disorders of renal function,
(c) increased cancer risk, (d) disorders of liver function, and (e) precipitated progression of coronar y artery disease. Conclusions.
e ndings of the present study suggest that there is currently no reasonable scientic basis in the literature to recommend protein
consumption above the current RDA (high protein diet) for healthy adults due to its potential disease risks. Further research needs
to be carried out in this area, including large randomized controlled trials.
1. Introduction
Protein is an essential macronutrient needed by the human
body for growth and maintenance. Foods rich in animal
proteinaremeat,sh,eggs,poultry,anddairyproducts,while
plant foods high in protein are mainly legumes, nuts, and
grains. e current recommended dietary allowance (RDA)
for protein is . g protein/kg body weight/day for adults (for
children . g protein/kg body weight/day, and for adolescents
. g protein/kg body weight/day) []. However, high protein
diets (dened as an intake above the current RDA) are
promoted intensively by the nutritional supplements industry
and they are considered to be “the gold standard” by many
athletes (especially bodybuilders) for muscle development
and/or body fat loss. On the other hand, several scientists
claim that the overuse of protein supplements or high dietary
protein intake could cause disorders to human health [].
e aim of this review study is to determine the potential
health dangers due to high protein/high meat intake obtained
from diet or nutritional supplements based on the human
studies existent in the literature. During the period of October
–May , a search was carried out in the databases
PubMed ( to present) and Google Scholar ( to
present). ere were included studies in English language
which had analyzed the potential health dangers due to long-
termhighproteinintakeobtainedfromdietornutritional
supplements in humans. e titles and the abstracts of the
initial studies identied were searched in order to determine
if they satisfy the selection criteria. e integral text of
selected titles was extracted and the reference list of selected
articles was consulted in order to nd out other relevant
publications.  studies ( experimental human studies and
 reviews) were identied which comprised data related
to the potential adverse eects of protein overconsumption
using the following search terms: “high protein diet,” “protein
overconsumption,” “protein overuse,” and “high meat diet.
e experimental human studies’ features included in the
study are conveyed in Tabl e  (reviews are not included).
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T : Disorders and health risks due to high protein/high meat intake (above .g protein/kg body weight/day) in adults.
ID Subjects Findings References
Bone and calcium homeostasis
 healthy adults Hypercalciuria []
 healthy adult males (a) Hypercalciuria, (b) negative calcium balance []
 healthy adult females (a) Hypercalciuria, (b) increased bone resorption []
 healthy adults (a) Decreased estimated calcium balance, (b) increased risk for bone loss []
, adult females Increased risk of forearm fracture []
 healthy adults and  patients
with nephrolithiasis (a) Hypercalciuria, (b) increased intestinal absorption of calcium []
 healthy adult males Hypercalciuria []
 healthy adult males Hypercalciuria []
 healthy adults Hypercalciuria []
  healthy adult males
(a) Hypercalciuria, (b) the consumption of high calcium diets is unlikely to
prevent the negative calcium balance and probable bone loss induced by
the consumption of high protein diets
[]
  healthy adult males Hypercalciuria []
  healthy adult males Hypercalciuria []
  adult females A decrease in vegetable protein intake and an increase in animal protein
intake increased bone loss and the risk of hip fracture []
Renal function
 healthyadultswithahistory
of renal stones
(a) Hyperuricosuria, (b) lower urine pH
(c) Increased risk of forming crystals or stones in the urine []
 healthy adults (a) Hyperuricosuria, (b) increased risk for uric acid stones []
 healthy adults (a) Increased acid load to the kidney, (b) increased risk for stone formation []
  adult females Accelerated renal function decline in women with mild renal insuciency []
  healthy adult males Increased overall relative probability of forming stones []
  healthy adult males (a) Hyperuricosuria, (b) decreased ability of urines to inhibit the
agglomeration of calcium oxalate crystals []
  healthy adult males (a) Ιncreased glomerular ltration rate, (b) decreased fractional renal
tubular reabsorption of calcium and urinary sodium []
Cancer risk
 , adult males Elevated risk of colon cancer was associated with high intake of red meat []
 , adult females High intake of red meat increases the risk of colon cancer []
 , adults Meat intake positively associated with cancer risk (stomach, colon, rectal,
pancreatic, bladder, breast, endometrial, and ovarian cancers) []
Liver function
  healthy adult males on high
protein supplements (a) Elevations in transaminases, (b) hyperalbuminemia []
Coronary blood ow
  adults Precipitated progression of coronary artery disease through increases in
lipid deposition and inammatory and coagulation pathways []
2. Disorders of Bone and Calcium Homeostasis
Diet which is high in protein generates a large amount of
acid in body uids []. e kidneys respond to this dietary
acid challenge with net acid excretion, and, concurrently,
the skeleton supplies buer by active resorption of bone
resultinginexcessivecalciumloss[]. Moreover, acid load-
ing directly inhibits renal calcium reabsorption leading to
hypercalciuria in combination with the exorbitant bone loss
[,]. In a metabolic study an increase in protein intake
fromabouttogcausedanincreaseinurinarycalcium
and a decrease in calcium retention. e data indicated
that protein-induced hypercalciuria was due to an elevation
in glomerular ltration rate and a lower fractional renal
tubularreabsorptionofcalcium,thelatterofwhichcaused
by the increased acid load on the renal tubular cells [].
Another study on subjects consuming diets containing  g
protein daily to  g showed that urinary calcium doubled,
while the calcium balance became negative []. In addition,
the eect of dietary protein on markers of bone turnover
has been evaluated []. In this study the subjects were
on a well-balanced diet for  weeks which was followed
ISRN Nutrition
by  days of an experimental diet containing one of three
levels of protein (low, medium, or high). Urinary calcium
excretion was signicantly higher, and urinary N-telopeptide
excretion (indicator of bone resorption) was signicantly
greater during the high protein than during the low protein
intake. Data suggested that, at high levels of dietary protein,
at least a portion of the increase in urinary calcium reected
increased bone resorption []. Additionally, subjects on a
low-carbohydrate high-protein (LCHP) diet for  weeks had
increased urinary calcium levels, decreased calcium balance,
and decreased serum osteocalcin concentrations []. In a
prospective study, protein was associated with an increased
risk of forearm fracture for women who consumed more than
 g per day compared with those who consumed less than
 g per day. Women who consumed ve or more servings
ofredmeatperweekalsohadasignicantlyincreased
risk of forearm fracture compared with women who ate
redmeatlessthanonceperweek[]. Furthermore, the
eect of high-protein diets on the excretion of calcium in
urinewasevaluatedinnormalpersonsandpatientswith
nephrolithiasis. All subjects were given diets containing . g
protein/kg/day, while, during the experimental phase, each
person received an additional . g protein/kg/day. ere was
a consistent increase in urinary calcium with the high-protein
diet averaging % above control in the normals and %
in the patients []. Moreover, in a study where protein
intake was varied from  g/day (low protein diet) to  g/day
(medium protein diet) and to  g/day (high protein diet) the
urinary calcium increased signicantly with each increase in
protein (, , and  mg, resp.) []. In addition, it has
been shown that increasing the protein intake from  to  g
daily caused a highly signicant elevation in urinary calcium,
the mean daily values being  and  mg, respectively [].
Inanotherstudytherelationshipofanimalproteinrichdietto
calcium metabolism was investigated during a -day dietary
period. An increase in urinary calcium excretion was found
indicating that the animal protein-induced calciuric response
could be a risk factor for the development of osteoporosis
[]. Notably, it has been shown that the consumption of
high calcium diets is unlikely to prevent the negative calcium
balance and probable bone loss induced by the consumption
of high protein diets (protein-induced hypercalciuria) []. In
this experiment (a -day metabolic study) subjects received
formula diets supplying  g nitrogen or g nitrogen, and
approximately  mg calcium per day. Overall calcium
balance was  mg/day on the  g nitrogen diet, and signif-
icantly lower at mg/dayinsubjectsconsumingthehigh
protein diet []. Additionally, dietary excess ( g/kg/day) in
animal protein for  week led to signicant changes in urinary
calcium excretion rates []. Furthermore, in an interesting
study the eects on urinary calcium levels of increasing
dietary protein from  to  g protein were compared
with those of increasing the sulfur amino acids to simulate
the amounts present in the  g protein diet. e increase
inproteinintakecausedurinarycalciumtodouble,while
sulfur amino acids added to the low protein diet also caused
urinary calcium to increase []. Moreover, a prospective
cohort study showed that a high ratio of dietary animal to
vegetable protein increases the rate of bone loss and the
risk of fracture in postmenopausal women. Animal foods
provide predominantly acid precursors, whereas protein in
vegetable foods is accompanied by base precursors not found
in animal foods. Imbalance between dietary acid and base
precursors leads to a chronic net dietary acid load that may
have adverse consequences on bone. An increase in vegetable
proteinintakeandadecreaseinanimalproteinintakemay
decrease bone loss and the risk of hip fracture [].
3. Disorders of Renal Function
Low uid intake and excessive intake of protein are important
risk factors for kidney stones []. Protein ingestion increases
renal acid excretion, and acid loads, in turn, may be buered
in part by bone, which releases calcium to be excreted by the
kidney. is protein-induced hypercalciuria could lead to the
formation of calcium kidney stones []. Furthermore, animal
protein is also the major dietary source of purines, the precur-
sors of uric acid. Excessive intake of animal protein is there-
fore associated with hyperuricosuria, a condition present in
some uric acid stone formers []. Uric acid solubility is largely
determined by the urinary pH. As the pH falls below .
to ., the solubility of uric acid decreases, and uric acid
precipitates, even if hyperuricosuria is not present []. e
pathobiochemical mechanisms of animal protein-induced
nephrolithiasis are shown in Figure . An interesting study on
the eects of protein overload on stone-forming propensity
showed that consumption of high-protein diet for  weeks
delivers a marked acid load to the kidney and increases the
risk for stone formation (urinary citrate levels decreased,
andurinarysaturationofundissociateduricacidincreased)
[]. Furthermore, in a study of three -day dietary periods
during which the diet of the subjects contained vegetable
protein, vegetable and egg protein, or animal protein, it was
found that the animal protein-rich diet was associated with
the highest excretion of undissociated uric acid due to the
reduction in urinary pH []. Moreover, citrate excretion was
reducedbecauseoftheacidload,andurinarycrystallization
studies revealed that the animal protein diet conferred an
increased risk for uric acid stones []. In another study it
was shown that a high protein intake induced changes in
urinary uric acid and citrate excretion rates and a decrease in
the ability of urines to inhibit calcium oxalate monohydrate
crystal agglomeration []. e decreased ability of urines
to inhibit the agglomeration of calcium oxalate crystals
could provide a possible physicochemical explanation for the
adverse eects of high-protein diet on renal stone formation
[]. Additionally, it has been indicated that high-protein
intake could cause increased glomerular ltration rate and
decreased fractional renal tubular reabsorption of calcium
and urinary sodium []. In another study, healthy subjects
withahistoryofrenalstonesfedonalow(LPD)anda
high (HPD) animal protein diet; aer  weeks it was found
that high dietary intake of purine-rich animal protein had
an impact on urinary urate excretion and supersaturation
in renal stone disease []. ere was an increase in urinary
urate, urinary acid excretion, ammonium ion excretion, and
uric acid supersaturation and a fall in urine pH on HPD.
e risk of forming uric acid or ammonium urate crystals or
ISRN Nutrition
High intake of protein
High acidogenic content
(sulfur-containing amino
acids)
High intake of purines,
the precursors of uric acid Decrease of urinary pH
Hyperuricosuria Decreased solubility
of uric acid
Uric acid kidney stones
Acid load is buered in part by
bone which releases calcium
to be excreted by the kidney
Hypercalciuria
Calcium kidney stones
F : Pathobiochemical mechanisms of animal protein-induced nephrolithiasis.
stones in the urine was increased on a high protein diet [].
Moreover, in a prospective cohort study it was investigated
whether protein intake inuences the rate of renal function
change over an -year period. e results showed that high
total protein intake, particularly high intake of nondairy ani-
mal protein, may accelerate renal function decline in women
with mild renal insuciency []. Furthermore, a study about
the short-term eect of increasing the dietary consumption of
animal protein on the urinar y risk factors for stone-formation
showed increased levels of urinary calcium and oxalate. e
accompanying increase in dietary purine caused an increase
in the excretion of uric acid. e overall relative probability
of forming stones, calculated from a combination of the
risk factors, was markedly increased (%) throughout the
period of high animal protein ingestion [].
4. Increased Cancer Risk, Disorders of Liver
Function, and Precipitated Progression of
Coronary Artery Disease
Up to % of breast, bowel, and prostate cancers are attributed
to dietary practices, and international comparisons show
positive associations with high meat diet []. e association,
however, seems to have been more consistently found for red
meat or processed meat and colorectal cancer []. Possible
mechanisms include the formation of heterocyclic amines in
meat when it is cooked. ese heterocyclic amines require
acetylation by P enzymes, and individuals with the fast-
acetylating genotype who eat high amounts of meat may be at
increased risk of large-bowel cancer []. It should be noticed
that red meat is the main dietary source of saturated fat, which
has been associated with breast and colorectal cancers [].
Moreover, NH3and N-nitroso compounds (NOC) formed
from residues by bacteria in the large bowel are probably
also important. NH3is a promotor of large-bowel tumours
chemically induced by NOC, and some of the chromosomal
mutations found in human colorectal cancer are consistent
with eects of NOC and heterocyclic amines []. In a cohort
study subjects who were free of diagnosed cancer com-
pleted a validated food frequency questionnaire and provided
detailed information on other lifestyle and health-related
factors. An elevated risk of colon cancer was associated with
red meat intake []. Men who ate beef, pork, or lamb as
a main dish ve or more times per week had an elevated
relative risk compared to men eating these foods less than
once per month. e association with red meat was not
confounded appreciably by other dietary factors, physical
activity, body mass, alcohol intake, cigarette smoking, or
aspirin use []. Furthermore, in a prospective study subjects
without a history of cancer, inammatory bowel disease, or
familial polyposis completed a dietary questionnaire [].
Aer adjustment for total energy intake, animal fat was
positively associated with the risk of colon cancer. e relative
ISRN Nutrition
risk of colon cancer in subjects who ate beef, pork, or lamb
as a main dish every day was increased, as compared with
those reporting consumption less than once a month [].
In an interesting study the overall data set derived from an
integrated series of case-control studies included histologi-
cally conrmed neoplasms; controls were patients admitted
to hospital for acute, nonneoplastic conditions unrelated to
long-term modications in diet []. e multivariate odds
ratios (ORs) for the highest tertile of red meat intake (
times/week) compared with the lowest ( times/week) were
. for stomach, . for colon, . for rectal, . for pancreatic,
. for bladder, . for breast, . for endometrial, and .
for ovarian cancers. us, reducing red meat intake might
lower the risk for several common neoplasms []. Moreover,
highprotein/high meat diet could cause disorders of liver
function and precipitated progression of coronary artery
disease. Hyperalbuminemia and elevated transaminases have
been associated with high-protein diet []. Individuals on
high protein supplements developed intermittent abdominal
pain, transient elevations in transaminases, and hyperalbu-
minemia without there being any identiable cause. e
symptoms and abnormalities on the laboratory tests resolved
aer the high protein intake was discontinued []. In a case-
control study, subjects (treatment group/TG) were studied
for  year by using myocardial perfusion imaging (MPI),
echocardiography (ECHO), and serial blood work []. MPI
andECHOwereperformedatthebeginningandendofthe
studyforeachindividual.eTGgroupstudiedmodied
their dietary intake as instructed. Additional subjects (high
protein group/HPG) elected a dierent dietary regimen
consisting of a “high-protein” diet []. Subjects in the
TG demonstrated a reduction in each of the independent
variables studied with regression in both the extent and
severity of coronary artery disease (CAD) as quantitatively
measured by MPI. Individuals in the HPG showed worsening
of their independent variables. ese results would suggest
that high-protein diets may precipitate progression of CAD
through increases in lipid deposition and inammatory and
coagulation pathways [].
5. Conclusions
Despite the fact that short-term high protein diet could
be necessary in several pathological conditions (malnutri-
tion, sarcopenia, etc.), it is evident that “too much of a
good thing” in diet could be useless or even harmful for
healthy individuals [,]. Many adults or even adolescents
(especially athletes or body builders) self-prescribe protein
supplements and overlook the risks of using them, mainly due
to misguided beliefs in their performance-enhancing abilities
[]. Individuals who follow these diets are therefore at risk
[]. Extra protein is not used eciently by the body and
may impose a metabolic burden on the bones, kidneys, and
liver. Moreover, high-protein/high-meat diets may also be
associated with increased risk for coronary heart disease due
tointakesofsaturatedfatandcholesterolorevencancer[].
Guidelines for diet should adhere closely to what has been
clinically proved, and by this standard there is currently no
basis to recommend high protein/high meat intake above
the recommended dietary allowance for healthy adults [
]. Further investigation with large randomized controlled
studies could provide more denitive evidence.
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... Indeed, protein is an essential macronutrient needed by the human body for growth and maintenance. However, high-protein diets are promoted intensively by the nutritional supplements industry for the loss of body fat and/or the development of muscles [8]. On the contrary, several researchers claim that high-dietary-protein intake could cause disorders [9]. ...
... Extra protein is not used efficiently by the body and may force a metabolic load onto various organs, such as kidneys and liver [8]. There is evidence that protein may raise the risk of coronary artery disease, stroke, diabetes and several types of cancer. ...
... An atherosclerotic effect from the LCHP diet was also confirmed in some previous studies [11,12]. Moreover, the high-meat diets may also be associated with higher risk for coronary heart disease as a result of intakes of cholesterol and saturated fat [8]. These conflicting results have initiated a debate over the benefits and risks of such diets and this is why our study concept was to enrich with 1% cholesterol, not only for the LCHP diet, but also the AIN-93G and Western diets, to determine the potential health consequences for the organism. ...
Article
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The aim of this study was to analyze the effect of a low-carbohydrate–high-protein diet, enriched with cholesterol (LCHPch), on body weight, lipid metabolism, as well as kidney and liver function in rats. Wistar rats (N = 18, male) were randomly allocated into experimental groups and fed a modified AIN-93G diet with the addition of 1% cholesterol (AINch, WDch and LCHPch diets) for 8 weeks. Despite the lack of significant differences in the final body weight and liver weight of animals, the kidneys of rats in the LCHPch group were considerably heavier compared to the control group. Serum total cholesterol and the sum of low- and very-low-density fractions of cholesterol as well as ALT activity were significantly increased in the LCHPch rats in comparison to the AINch group. Simultaneously, the highest content of liver fat was obtained for animals from LCHPch group. It was also shown that both WDch and LCHPch diets significantly changed fatty acid profile in the adipose tissue of rats compared to control, with a significant increase in SFA and MUFA and a decrease in PUFA. Non-alcoholic fatty liver disease was observed in rats fed not only WDch but also LCHPch diets. The detailed mechanism still needs to be investigated to prevent the organism from the harmful effects of macronutrient dietary imbalance.
... Protein overconsumption (i.e., protein that is nutritionally unnecessary) in western countries has been widely reported [11][12][13] and is far above the Population Reference Intake (PRI) [14]. There is a clear rationale to decrease the daily intake of protein since a substantial body of evidence associates the overconsumption of protein with adverse effects on human health, such as disorders of bone and calcium homeostasis, renal and liver dysfunction, increased cancer risk, hyperalbuminemia and precipitated progression of coronary artery disease [15][16][17][18][19][20]. Refs. ...
... [21,22], therefore, suggest a 'reversed' diet transition by 'using less' (e.g., leaving the meat out of the dish) or 'doing things differently' by a diet reformulation strategy, with reduced protein content in food products appears to be the most effective approach. However, plans to convince free and affluent societies to eat healthy but not innately desired food have been largely unsuccessful in the past [15][16][17][18][19][20][21][22]. Since the beginning of nutritional science, it has been hypothesised that the nutrients ingested through our diet are not entirely absorbed in the body, and only part of them are available. ...
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Several global health risks are related to our dietary lifestyle. As a consequence of the overconsumption of ultra-processed and highly digestible protein (150–200% of the recommended value), excess dietary proteins reach the colon, are hydrolysed to peptides and amino acids by bacterial proteases and fermented to various potentially toxic end products. A diet reformulation strategy with reduced protein content in food products appears to be the most effective approach. A potential approach to this challenge is to reduce food digestibility by introducing resistant protein into the diet that could positively influence human health and gut microbiome functionality. Resistant protein is a dietary constituent not hydrolysed by digestive enzymes or absorbed in the human small intestine. The chemical conformation and the amino acid composition strictly influence its structural stability and resistance to in vivo proteolysis and denaturation. Responding to the important gap in our knowledge regarding the digestibility performance of alternative proteins, we hypothesise that resistant proteins can beneficially alter food functionality via their role in improving metabolic properties and health benefits in human nutrition, similar to fibres and resistant starches. A multidisciplinary investigation of resistant protein will generate tremendous scientific impact for other interlinked societal, economic, technological and health and wellbeing aspects of human life.
... Therefore, an apprehension may be associated with consuming these protein-rich foods (Delimaris, 2013). Evidence suggests that consuming food containing amyloids or amyloid-like aggregates enhances the probability of onset of protein misfolding diseases, particularly in the susceptible individual. ...
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Purified soya bean proteins (glycinin and conglycinin) are known to form amyloid‐like aggregates in vitro at a higher temperature. Soya beans (chunks) are textured proteinaceous vegetables made from defatted soya flour by heating it above 100°C and extruding under high pressure. Therefore, it was assumed that subjecting the soya bean proteins to high temperatures raises the possibility of forming amyloids or amyloid‐like protein aggregates. Hence, the present study aimed to examine the presence of amyloid‐like protein aggregates in soya beans. The isolated protein aggregates from hydrated soya beans displayed typical characteristics of amyloids, such as the red shift in the absorption maximum (λmax) of Congo red (CR), high Thioflavin T (ThT), and 8‐Anilinonapthalene‐1‐sulfonate (ANS) binding, and fibrilar morphology. Furthermore, these aggregates were found to be stable against proteolytic hydrolysis, confirming the specific property of amyloids. The presence of amyloid‐like structures in soya beans raises concerns about their implications for human nutrition and health. Practical applications Protein aggregation has usually been considered detrimental. The traditional food‐processing conditions, such as thermal processing, are associated with protein denaturation and aggregation. The formation of ordered protein aggregates with extensive β‐sheet are progressively evident in various protein‐rich foods known as amyloid, which expands food safety concerns. Instead, it is also associated with poor nutritional characteristics. The present study concerns the presence of amyloid‐like protein aggregates in widely consumed native soya beans, which are manufactured by extensive heat treatment of defatted soy flour. Although there is no indication of their toxicity, these aggregates are found to be proteolytically resistant. The seminal findings in this manuscript suggest that it is time to adapt innovative food processing and supplementation of bioactive molecules that can prevent the formation of such protein aggregates and help maximize the utilization of protein‐based nutritional values.
... Protein is a nutrient genuinely essential for life, but whilst there are good reasons to encourage an adequate intake of it, high intake of protein, most notably of animal origin, has been linked to many of the modern day chronic diseases (Delimaris, 2013;Dong, Gao et al., 2020;Naghshi, Sadeghi et al., 2020), whilst varied and balanced plant-based eating patterns have been shown to help in the prevention of many of them (Kim, Caulfield et al., 2019;Tuso, Ismail et al., 2013). From a health standpoint, meat alternatives are not all free of some of the issues encountered by the products they intend to replace, as they generally are ultra-processed foods, which higher consumption has been linked to low diet quality (Martini et al., 2021). ...
Article
Background The drive to reduce the negative impact of the global food system on the environment and human health, and to feed a growing global population, has led to the rapid development of meat alternatives, including plant-based and mycoprotein-based products such as burgers, cured meat and nuggets. These are generally food items manufactured with highly refined ingredients, so health professionals interested in promoting plant-based diets, or a reduction in meat consumption, need a deeper understanding about the potential health effects of these products in order to present them to the public in an objective and helpful manner. Scope and approaches In this narrative review, a search of the current available scientific literature was performed with the aim of exploring all these foods by delving into the way they are manufactured, their nutritional characteristics, their impact on health, as well as trying to understand their place in modern, diets. Key findings and conclusion Processed meat alternatives, despite being highly refined products, can be a good source of healthy food groups and nutrients often underrepresented in omnivores diets such as grains, legumes, plant protein and fibre, although attention must be paid to their salt and saturated fat content. For people wanting to move away from a meat-heavy diet, the consumption of these items can represent a stepping stone towards the adoption of more healthful dietary patterns centred on whole plant-foods. In addition, they might help to increase compliance with the new lifestyle as they tend to replicate some of the organoleptic properties of meat.
... In general, the human body needs between 1.0 g to 1.5g of protein for each kilogram of weigh in children and adults respectively [5]. If there is insufficient protein in diet chronically that could cause kwashiorkor disease, which is a severe form of malnutrition [6]. ...
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Background: Fermentation is a sort of biotechnology that uses microorganisms to produce animal food through chemical process. In ancient times, wastes were treated with chemicals, but now companies convert wastes to valuable food, food ingredients or feed products such as single cell oils or single cell protein. The most used substrate is molasses and corn steep liquor which is a part of the fermentation process. Aim: The aims of the manuscript is to provide an overview of the yeast strains and food by-products used in production of single cell proteins by fermentation process. Furthermore, the manuscript summarizes the role of single cell protein in animal feed. Methods: Electronic searches were conducted on Google Scholar database Medline and PubMed. A further search was conducted on the Food and agricultural organisation FAO research article database. Results: Single cell protein produced by these substrates and different microorganisms (algae, yeast, bacteria) play an important role in animal feeding. Furthermore, SCP is a high-quality protein, unsaturated fatty acids, vitamins and minerals sources for animals. Conclusion: Production of single cell of protein through the fermentation has several significant benefits including sustainability, health and production efficacy.
... Methods for the enrichment of protein preparations have already been developed [28][29][30][31]. Nevertheless, high protein intake is not advisable in some diets [32]. Consumers may also show little confidence in high-protein preparations, associating them with the diets of physically active people rather than as a standard part of everyday diet [33][34][35]. ...
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This study aimed to determine the use of selected vegetables (pumpkin, cauliflower, broccoli , carrot) as carriers of potassium iodide (KI) and potassium iodate (KIO3) by determining changes in iodine content under various conditions of impregnation as the degree of hydration, impregnated sample temperature, and impregnation time. The influence of these conditions on iodine contents in vegetables after their fortification and storage (21 °C/230 days) was analyzed. The results showed that all selected vegetables could be efficient iodine carriers. However, the conditions of the impregnation process are crucial for fortification efficiency, particularly the degree of hydration and the temperature of the impregnated samples before drying. The results showed that the lowest iodine content was in samples fortified at 4 °C and 1:4 hydration. On the other hand, the highest reproducibility of iodine was for the following fortification conditions: temperature of −76 °C and hydration of 1:1. The studies confirmed the higher stability of iodine in KIO3 form compared to KI. To increase recovery of the introduced iodine in the product after drying, using the conditioning step at 4 °C is not recommended. We recommend freezing vegetables immediately after the impregnation process
... These data in model organisms go against trending dietary advice for humans, which has generally recommended that humans should be eating more protein to improve satiety and promote weight loss (Cuenca-Sanchez et al., 2015;Yu et al., 2020). High protein diets are indeed indicated for certain clinical conditions or life stages, such as pregnancy and old age, but epidemiological evidence suggests that overconsumption of protein outside of these conditions could be deleterious (Delimaris, 2013). A randomized controlled trial (RCT) of overfeeding in metabolically healthy individuals with low, normal, or high protein content found that low protein feeding resulted in significantly less weight gain, though this was a result of lack of lean mass gain rather than reduced fat gain (Bray et al., 2012). ...
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The proportion of humans suffering from age‐related diseases is increasing around the world, and creative solutions are needed to promote healthy longevity. Recent work has clearly shown that a calorie is not just a calorie—and that low protein diets are associated with reduced mortality in humans and promote metabolic health and extended lifespan in rodents. Many of the benefits of protein restriction on metabolism and aging are the result of decreased consumption of the three branched‐chain amino acids (BCAAs), leucine, isoleucine, and valine. Here, we discuss the emerging evidence that BCAAs are critical modulators of healthy metabolism and longevity in rodents and humans, as well as the physiological and molecular mechanisms that may drive the benefits of BCAA restriction. Our results illustrate that protein quality—the specific composition of dietary protein—may be a previously unappreciated driver of metabolic dysfunction and that reducing dietary BCAAs may be a promising new approach to delay and prevent diseases of aging. Creative solutions are needed to combat increasing rates of metabolic disease and promote healthy aging. This review summarizes the latest research on protein and branched‐chain amino acid restriction as interventions to alter metabolism to extend lifespan and reduce frailty in model organisms and humans. The authors discuss the potential mechanisms underpinning these dietary interventions and postulate future directions of the field, which may include personalized nutrition therapy.
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The Asteraceae family includes species used for food or medicinal remedies, one of which is Lagascea decipiens, which is native to the Sierra Madre Occident in Mexico. Because this plant has not been previously characterized, its biochemical components and antioxidant and antimicrobial activities were quantified in its flowers, leaves and stems. The leaves are sources of ash (20.37 g/100 g dry weight) and the flowers of total lipids (7.32 g/100 g dry weight). According to their fatty acid profile, the leaves provide polyunsaturated fatty acids (63.25%), the most abundant of which is alpha-linolenic acid. Leaves are the main source of essential amino acids (55.58 ± 0.05 mg/g dry weight) and α-tocopherol (201.96 ± 19.68 µg/g dry weight). The antioxidant activity against the radical DPPH was higher in the flowers (20.04 ± 0.04 µmol eq. of Trolox/g of extract dry weight) than in other parts. The aqueous or alcoholic extracts of the plant did not show activity against selected microorganisms. Due to their biochemical components and antioxidant activity, the leaves and flowers of the native plant L. decipiens have potential for use in the food and medicinal industries.
Chapter
Among mental health diseases, depression is a global problem with a high prevalence for elderly patients and is directly related to the nutritional status. Depression of older people is considered as a psychological phenomenon with consequences for nutrition, additionally nutrition disorder can conduce to psychological effects. Scientists have identified essential nutritional factors, which can lead in case of deficiency to depression. Among these nutritional factors, some water-soluble and fat-soluble vitamins, minerals, polyunsaturated fatty acids, polyphenols, as well as proteins were identified. This review highlights the relationship between balanced diets in elderly people and the risk of depression.
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Purpose: Nitrogen (N2) is an indispensable metabolite required for the synthesis of protein. In animals, gut bacteria and, to a certain extent, even hepatocytes, are able to assimilate nitrogen from ammonium (NH4+), which is essentially derived from the amine group (-NH2) and which is at the same time a very toxic metabolite. Initially, NH4+ is coupled to alpha-ketoglutarate (AKG), a reaction which results in the appearance of glutamate (one amine group), and after that, in the appearance of glutamine - containing two amine groups. The surplus of NH4+ which is not utilized by AKG/glutamate/glutamine is eliminated as urea in the urine, via the urea cycle in hepatocytes. Plants bacteria also assimilate nitrogen from NH4+, by its fixation to ammonia (NH3)/NH4+. Materials/methods: Previous studies have shown that AKG (also known as 2-oxo-glutaric acid or 2-oxopentanedioic acid), the primary metabolite of Rhizobium and gut bacteria, is essential for the assimilation of nitrogen. Results: Symbiotic bacteria produce AKG, which together with glutamate dehydrogenase (GDH), 'generates' primarily amine groups from NH4+. The final product is glutamate - the first amino acid. Glutamate has the capacity to be converted to glutamine, through the action of glutamine synthetase, after the assimilation of the second nitrogen from NH4+. Conclusion: Glutamate/glutamine, derivatives of AKG metabolism, are capable of donating amine groups for the creation of other amino acids, following NH2 transamination to certain metabolites e.g., short chain fatty acids (SCFA).
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The evidence that red and processed meat influences colorectal carcinogenesis was judged convincing in the 2007 World Cancer Research Fund/American Institute of Cancer Research report. Since then, ten prospective studies have published new results. Here we update the evidence from prospective studies and explore whether there is a non-linear association of red and processed meats with colorectal cancer risk. Relevant prospective studies were identified in PubMed until March 2011. For each study, relative risks and 95% confidence intervals (CI) were extracted and pooled with a random-effects model, weighting for the inverse of the variance, in highest versus lowest intake comparison, and dose-response meta-analyses. Red and processed meats intake was associated with increased colorectal cancer risk. The summary relative risk (RR) of colorectal cancer for the highest versus the lowest intake was 1.22 (95% CI  =  1.11-1.34) and the RR for every 100 g/day increase was 1.14 (95% CI  =  1.04-1.24). Non-linear dose-response meta-analyses revealed that colorectal cancer risk increases approximately linearly with increasing intake of red and processed meats up to approximately 140 g/day, where the curve approaches its plateau. The associations were similar for colon and rectal cancer risk. When analyzed separately, colorectal cancer risk was related to intake of fresh red meat (RR(for 100 g/day increase)  =  1.17, 95% CI  =  1.05-1.31) and processed meat (RR (for 50 g/day increase)  =  1.18, 95% CI  =  1.10-1.28). Similar results were observed for colon cancer, but for rectal cancer, no significant associations were observed. High intake of red and processed meat is associated with significant increased risk of colorectal, colon and rectal cancers. The overall evidence of prospective studies supports limiting red and processed meat consumption as one of the dietary recommendations for the prevention of colorectal cancer.
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The rates of colon cancer in various countries are strongly correlated with the per capita consumption of red meat and animal fat and, to a lesser degree, inversely associated with the consumption of fiber. We conducted a prospective study among 88,751 women 34 to 59 years old and without a history of cancer, inflammatory bowel disease, or familial polyposis who completed a dietary questionnaire in 1980. By 1986, during 512,488 person-years of follow-up, 150 incident cases of colon cancer had been documented. After adjustment for total energy intake, animal fat was positively associated with the risk of colon cancer (P for trend = 0.01); the relative risk for the highest as compared with the lowest quintile was 1.89 (95 percent confidence interval, 1.13 to 3.15). No association was found for vegetable fat. The relative risk of colon cancer in women who ate beef, pork, or lamb as a main dish every day was 2.49 (95 percent confidence interval, 1.24 to 5.03), as compared with those reporting consumption less than once a month. Processed meats and liver were also significantly associated with increased risk, whereas fish and chicken without skin were related to decreased risk. The ratio of the intake of red meat to the intake of chicken and fish was particularly strongly associated with an increased incidence of colon cancer (P for trend = 0.0005); the relative risk for women in the highest quintile of this ratio as compared with those in the lowest quintile was 2.49 (95 percent confidence interval, 1.50 to 4.13). A low intake of fiber from fruits appeared to contribute to the risk of colon cancer, but this relation was not statistically independent of meat intake. These prospective data provide evidence for the hypothesis that a high intake of animal fat increases the risk of colon cancer, and they support existing recommendations to substitute fish and chicken for meats high in fat.
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Background: Different sources of dietary protein may have different effects on bone metabolism. Animal foods provide predominantly acid precursors, whereas protein in vegetable foods is accompanied by base precursors not found in animal foods. Imbalance between dietary acid and base precursors leads to a chronic net dietary acid load that may have adverse consequences on bone. Objective: We wanted to test the hypothesis that a high dietary ratio of animal to vegetable foods, quantified by protein content, increases bone loss and the risk of fracture. Design: This was a prospective cohort study with a mean (±SD) of 7.0 ± 1.5 y of follow-up of 1035 community-dwelling white women aged >65 y. Protein intake was measured by using a food-frequency questionnaire and bone mineral density was measured by dual-energy X-ray absorptiometry. Results: Bone mineral density was not significantly associated with the ratio of animal to vegetable protein intake. Women with a high ratio had a higher rate of bone loss at the femoral neck than did those with a low ratio (P = 0.02) and a greater risk of hip fracture (relative risk = 3.7, P = 0.04). These associations were unaffected by adjustment for age, weight, estrogen use, tobacco use, exercise, total calcium intake, and total protein intake. Conclusions: Elderly women with a high dietary ratio of animal to vegetable protein intake have more rapid femoral neck bone loss and a greater risk of hip fracture than do those with a low ratio. This suggests that an increase in vegetable protein intake and a decrease in animal protein intake may decrease bone loss and the risk of hip fracture. This possibility should be confirmed in other prospective studies and tested in a randomized trial.
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Kidney Stones is an elegant book of over 1100 pages about an ancient disease, which was already known to Hippocrates. Montaigne thought stone disease was "a noble and dignified malady [that] attacked the great for preference." Samuel Pepys suffered from recurrent urinary calculi, and so may have Sir Walter Scott when he gloomily predicted that his making blood might soon lead to making earth. Also afflicted was Napoleon III, dying of uremia just over a century ago. Today we know much more about this disease that affects 12% to 20% of American men and, 5% to 10% of women during their lifetimes. Most of this knowledge is well covered in this book's 51 readable chapters, authoritatively written and well illustrated."... considering the physical characteristics of urine, it is surprising that kidney stones do not occur more often."Obviously few clinicians require such a large book to competently manage kidney stones.
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When calcium and phosphorus intakes were maintained con stant at 1400 mg daily, increasing the protein intake of 18-to-20-year-old males from 48 to 141 g daily caused a highly significant increase in urinary calcium, the mean daily values being 175 and 338 mg, respectively. The apparent absorp tion of calcium was higher by 69 mg daily when the high protein diet was fed, although this effect was not statistically significant. The effect of protein intake on calcium retention approached significance (P
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Urine calcium excretion is known to be directly correlated with the level of dietary protein intake. In this experiment we examined the persistence of the hypercalciuria induced by the consumption of high protein diets, and the mechanism of the calciuric response. In a 95-day metabolic study, each of six adult male subjects received formula diets supplying 12 g nitrogen or 36 g nitrogen, and approximately 1400 mg calcium per day. Urine calcium increased rapidly and significantly from an average of 191 mg/day on the 12 g nitrogen diet to 277 mg/day on the 36 g nitrogen diet. There was no significant difference in the apparent absorption of calcium, so that overall calcium balance was -37 mg/day on the 12 g nitrogen diet, and significantly lower at -137 mg/day in subjects consuming the high protein diet. Levels of urinary hydroxyproline, serum insulin, and parathyroid hormone were not significantly increased by high intakes of protein. A decrease in the fractional reabsorption of calcium by the kidney seems to be the most likely cause of the protein-induced hypercalciuria. The consumption of high calcium diets is unlikely to prevent the negative calcium balance and probable bone loss induced by the consumption of high protein diets.
Article
Mechanisms involved in the hypercalciuria caused by high levels of protein intake were investigated. Six healthy males participated in a 20-day metabolic study. During the first 10-day period, all subjects were given a 47 g protein diet and during the second 10-day period, a 142 g protein diet. Calcium, magnesium and phosphorus intakes were kept constant at 515, 320 and 1,110 mg daily, respectively. Urinary calcium was elevated significantly when the protein intake was increased. Glomerular filtration rate and calcium clearance were increased significantly when the high protein diet was fed; the fractional tubular reabsorption of calcium was decreased from 98.4 to 97.4%. Thus, the increase in urinary calcium caused by the high protein diet appears to be due in part to an increase in the filtered load of calcium by the glomeruli and in part to a decrease in calcium reabsorption by the renal tubules. The level of protein intake had no effect on the fasting serum concentrations of parathyroid hormone, total calcium, magnesium or inorganic phosphorus or plasma ultrafiltrable calcium.
Article
The effect of high-protein diets on the excretion of calcium in urine was evaluated in four normal persons and in four patients with nephrolithiasis. All subjects were housed in a metabolic unit and given constant metabolic diets each day containing 0.5 g protein/kg and 300–600 mg calcium, 1000 mg phosphorus, and 69 mEq sodium. During the experimental phase, each person received an additional 1.5 g protein/kg/day consisting of purified casein, gluten, lactalbumin, and gelatin. There was a consistent increase in urinary calcium with the high-protein diet, averaging 88% above control in the normals and 82% in the patients. In addition, the normal subjects showed significant (p < 0.05) increases in urinary phosphorus (mean increases, 219 ± 53 mg/d, mean ± SE), nitrogen (8.8 ± 0.9 g/d), titratable acid (19 ± 5 mEq/d), and ammonium (22 ± 3 mEq/d), whereas the patients showed increases in urinary magnesium (18 ± 2 mg/d), nitrogen (12 ± 1.0 g/d), and ammonium (34 ± 2 mEq/d), and in creatinine clearance (14 ± 3 ml/min). In both groups, there was a small increase in the filtered, excreted, and reabsorbed calcium and a small decrease in the percentage reabsorption of calcium. Serum chemical values did not change from values with the low-protein diet. In two of the patients who were known to be hyperabsorbing calcium, sodium cellulose phosphate (chelator of intestinal calcium) reversed the increase in urinary calcium produced by the high-protein diet. In the remaining patients, neither sodium cellulose phosphate nor a low-calcium diet could counteract the increase in excretion of calcium with the diet. It is concluded that a high-protein diet can increase urinary calcium by altering renal function and/or increasing intestinal absorption of calcium and that dietary protein must be considered in the evaluation and treatment of patients with hypercalciuria and nephrolithiasis.
Article
1. Studies were carried out on six normal male subjects to determine the short-term effect of increasing the dietary consumption of animal protein on the urinary risk factors for stone-formation, namely, volume, pH, calcium, oxalate, uric acid and glycosaminoglycans. 2. An increase of 34 g/day of animal protein in the diet significantly increased urinary calcium (23%) and oxalate (24%). Total urinary nitrogen increased by an average of 368 mmol/day. The accompanying increase in dietary purine (11 mmol of purine nitrogen/day) caused a 48% increase in the excretion of uric acid. 3. The overall relative probability of forming stones, calculated from a combination of the risk factors, was markedly increased (250%) throughout the period of high animal protein ingestion.