Essential amino
acid
An
essential amino acid: this is also known as indispensable amino acid.
It is an amino acid that cannot be synthesized de novo (from scratch) by
the organism, and thus must be supplied in its diet. There are nine amino acids
that humans cannot synthesize and they include: (PHIL2T2-MV): phenylalanine, histidine, isoleucine, leucine, lysine threonine, tryptophan, methionine and valine,
Conditionally
essential amino acids: these are amino acids whose synthesis can be limited
under special pathophysiological conditions, such as prematurity in the infant
or individuals in severe catabolic distress. The six conditionally essential
amino acids are (PACT-G2): proline, arginine, cysteine, tyrosine, glutamine, glycine.
Non
essential amino acids (dispensable amino acids) : these are amino
acids that can be synthesized in the body. There are five non essential amino
acids nmaely: (GA3S): glutamic acid, alanine, asparagine, aspartic acid, and serine
Essentiality in humans
|
Essential
|
Non-Essential
|
|
Histidine (H)
|
Alanine (A)
|
|
Isoleucine (I)
|
Arginine* (R)
|
|
Leucine (L)
|
Aspartic acid (D)
|
|
Lysine (K)
|
Cysteine* (C)
|
|
Methionine (M)
|
Glutamic acid (E)
|
|
Phenylalanine (F)
|
Glutamine* (Q)
|
|
Threonine (T)
|
Glycine* (G)
|
|
Tryptophan (W)
|
Proline* (P)
|
|
Valine (V)
|
Serine* (S)
|
|
Tyrosine* (Y)
|
|
|
Asparagine* (N)
|
|
|
Selenocysteine (U)
|
|
|
Pyrrolysine** (O)
|
Eukaryotes can synthesize some
of the amino acids from other substrates. Consequently, only a subset of the
amino acids used in protein synthesis are essential nutrients.
Minimum daily intake
Main
article: Protein (nutrient)
Estimating
the daily requirement for the indispensable amino acids has proven to be
difficult; these numbers have undergone considerable revision over the last 20
years. The following table lists the WHO recommended daily amounts currently in
use for essential amino acids in adult humans, together with their
standard one-letter abbreviations.[6] Food sources are
identified based on the USDA National Nutrient
Database Release.
|
Amino acid(s)
|
mg per kg body weight
|
mg per 70 kg
|
mg per 100 kg
|
|
10
|
700
|
1000
|
|
|
20
|
1400
|
2000
|
|
|
39
|
2730
|
3900
|
|
|
30
|
2100
|
3000
|
|
|
+
C Cysteine
|
10.4
+ 4.1 (15 total)
|
1050
|
1500
|
|
+
Y Tyrosine
|
25
(total)
|
1750
|
2500
|
|
15
|
1050
|
1500
|
|
|
4
|
280
|
400
|
|
|
26
|
1820
|
2600
|
The
recommended daily intakes for children aged three years and older is 10% to 20%
higher than adult levels and those for infants can be as much as 150% higher in
the first year of life. Cysteine (or
sulphur-containing amino acids), tyrosine (or aromatic amino
acids), and arginine are always required
by infants and growing children.[6][7]
Relative amino acid composition of
protein sources
Various
attempts have been made to express the "quality" or "value"
of various kinds of protein. Measures include the biological value, net protein
utilization,
protein efficiency ratio, protein digestibility-corrected amino
acid score
and complete proteins
concept.
These concepts are important in the livestock industry, because the relative
lack of one or more of the essential amino acids in animal feeds would have a
limiting effect on growth and thus on feed conversion
ratio.
Thus, various feedstuffs may be fed in combination to increase net protein
utilization, or a supplement of an individual amino acid (methionine, lysine,
threonine, or tryptophan) can be added to the feed.
Although
proteins from plant sources tend to have a
relatively lower concentrations of protein by mass in comparison to protein
from eggs or milk, they are nevertheless "complete" in that they
contain at least trace amounts of all of the amino acids that are essential in
human nutrition.[8] Eating various plant
foods in combination can provide a protein of higher biological value.[9] Certain native
combinations of foods, such as corn and beans, soybeans and rice, or red beans
and rice, contain the essential amino acids necessary for humans in adequate
amounts.[10]
Additionally,
certain types of algae and marine phytoplankton predate the division between
animal and plant life on the planet; they have both chlorophyll as do plants,
and also all the essential amino acids, as do animal proteins.
Protein per calorie
It
can be shown that common vegetable sources contain adequate protein, often more
protein per Calorie than the standard reference, whole raw egg, while other
plant sources, particularly fruits contain less. For example, while 100 g of
raw broccoli only provides 28 kcal and 3 g of protein, it has over 100 mg
of protein per kcal. An egg contains five times as many calories (143 kcal) but
only four times as much protein, roughly 90 mg of protein per kcal.
However, a carrot has only 23 mg protein per kcal or twice the minimum
recommendation, a banana meets the minimum, and an apple is below
recommendation.[11] It is recommended
that adult humans obtain 10–35% of their calories as protein, or roughly
11–39 mg of protein per kcal per day (22–78 g for 2000 kcal).[12] The US FDA daily
reference value of 50 g protein per 2000 kcal is 25 mg/kcal per day.[13]
|
Source
|
protein (g)
|
Calories (kcal)
|
protein/Calorie
(mg / kcal) |
L (mg)
|
T (mg)
|
W (mg)
|
M+C (mg)
|
|
Apples, raw (100 g)
|
0.26
|
52
|
5
|
12
|
6
|
1
|
2
|
|
Minimum daily reference
|
22
|
2000
|
11
|
||||
|
Bananas, raw (100 g)
|
1
|
89
|
12
|
500
|
28
|
9
|
17
|
|
Carrot, raw (100 g)
|
1
|
41
|
23
|
101
|
191
|
12
|
103
|
|
US FDA daily / WHO (70 kg)
|
50
|
2000
|
25
|
2730
|
1050
|
280
|
1050
|
|
Upper daily reference
|
78
|
2000
|
39
|
||||
|
Peanut, valencia, raw (100 g)
|
48
|
570
|
84
|
1,627
|
859
|
244
|
630
|
|
Soybeans, dry (100 g)
|
40
|
451
|
88
|
2634
|
1719
|
575
|
1172
|
|
Egg, whole, raw (100 g)
|
13
|
143
|
91
|
912
|
556
|
167
|
652
|
|
Broccoli, raw (100 g)
|
3
|
28
|
107
|
141
|
91
|
29
|
54
|
|
Soy Sauce, typical (100 g)
|
11
|
60
|
175
|
729
|
403
|
182
|
576
|
|
Beef, grass-fed, lean (100 g)
|
23
|
117
|
197
|
Complete proteins in non-human animals
Scientists
had known since the early 20th century that rats could not survive on a diet
whose only protein source was zein, which comes from maize (corn), but recovered if they were fed
casein from cow's milk.
This led William Cumming Rose to the discovery of
the essential amino acid threonine.[14] Through manipulation
of rodent diets, Rose was able to show that ten amino acids are essential for
rats: lysine, tryptophan, histidine, phenylalanine, leucine, isoleucine, methionine, valine, and arginine, in addition to
threonine. Rose's later work showed that eight amino acids are essential for
adult human beings, with histidine also being essential for infants. Longer
term studies established histidine as also essential for adult humans.[15]
Interchangeability
The
distinction between essential and non-essential amino acids is somewhat
unclear, as some amino acids can be produced from others. The sulfur-containing amino
acids, methionine and homocysteine, can be converted
into each other but neither can be synthesized de novo in humans.
Likewise, cysteine can be made from homocysteine but cannot be synthesized on
its own. So, for convenience, sulfur-containing amino acids are sometimes
considered a single pool of nutritionally equivalent amino acids as are the aromatic amino acid pair, phenylalanine and tyrosine. Likewise arginine, ornithine, and citrulline, which are
interconvertible by the urea cycle, are considered a single
group.[citation needed]
Effects of deficiency
Main
article: Protein-energy malnutrition
If
one of the nonessential amino acids is less than needed for an individual the
utilization of other amino acids will be hindered and thus protein synthesis
will be less than what it usually is, even in the presence of adequate total
nitrogen intake.[2]
Protein
deficiency has been shown to affect all of the body's organs and many of its
systems, including the brain and brain function of infants and young children;
the immune system, thus elevating risk of infection; gut mucosal function and
permeability, which affects absorption and vulnerability to systemic disease;
and kidney function.[2] The physical signs
of protein deficiency include edema, failure to thrive in infants and children,
poor musculature, dull skin, and thin and fragile hair. Biochemical changes
reflecting protein deficiency include low serum albumin and low serum
transferrin.[2]
The
amino acids that are essential in the human diet were established in a series
of experiments led by William Cumming Rose. The experiments
involved elemental diets to healthy male graduate students. These diets
consisted of cornstarch, sucrose, butterfat without protein, corn oil,
inorganic salts, the known vitamins, a large brown "candy" made of
liver extract flavored with peppermint oil (to supply any unknown vitamins),
and mixtures of highly purified individual amino acids. The main outcome
measure was nitrogen balance. Rose noted that the
symptoms of nervousness, exhaustion, and dizziness were encountered to a
greater or lesser extent whenever human subjects were deprived of an essential
amino acid.[16]
Essential
amino acid deficiency should be distinguished from protein-energy malnutrition, which can manifest
as marasmus or kwashiorkor. Kwashiorkor was
once attributed to pure protein deficiency in individuals who were consuming
enough calories ("sugar baby syndrome"). However, this theory has
been challenged by the finding that there is no difference in the diets of
children developing marasmus as opposed to kwashiorkor.[17] Still, for instance
in Dietary Reference Intakes (DRI) maintained by
the USDA, lack of one or more
of the essential amino acids is described as protein-energy malnutrition.[2]
Amino acids
Amino
acids are organic compounds that combine to form proteins. Amino acids and proteins are the
building blocks of life.
When
proteins are digested or broken down, amino acids are left. The human body uses
amino acids to make proteins to help the body:
- Break down food
- Grow
- Repair body tissue
- Perform many other body functions
Amino
acids can also be used as a source of energy by the body.
Amino
acids are classified into three groups:
- Essential amino acids
- Nonessential amino acids
- Conditional amino acids
Essential
amino acids
- Essential amino acids cannot be made by the body. As a result, they must come from food.
- The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Nonessential
amino acids
- "Nonessential" means that our bodies produce an amino acid, even if we do not get it from the food we eat.
- Nonessential amino acids include: alanine, asparagine, aspartic acid, and glutamic acid.
Conditional
amino acids
- Conditional amino acids are usually not essential, except in times of illness and stress.
- Conditional amino acids include: arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.
You
do not need to eat essential and nonessential amino acids at every meal, but
getting a balance of them over the whole day is important. A diet based on a
single plant item will not be adequate but we no longer worry about pairing
proteins (such as beans with rice) at a single meal. Instead we look at the
adequacy of the diet overall throughout the day.
References
|
Essential Amino Acids
Amino acids are organic
compounds which contain both an amino group and a carboxyl group. According
to Tillery, et al., the human body can synthesize all of the amino acids
necessary to build proteins except for the ten called the "essential
amino acids", indicated by asterisks in the amino acid illustrations. An adequate diet
must contain these essential amino acids. Typically, they are supplied by
meat and dairy products, but if those are not consumed, some care must be
applied to ensuring an adequate supply. They can be supplied by a combination
of cereal grains (wheat, corn, rice, etc.) and legumes (beans,peanuts, etc.).
Tillery points out that a number of popular ethnic foods involve such a
combination, so that in a single dish, one might hope to get the ten
essential amino acids. Mexican corn and beans, Japanese rice and soybeans,
and Cajun red beans and rice are examples of such fortuitous combinations.
  
The
University of Arizona's Biology Project gives the following summary:"The
10 amino acids that we can produce are alanine, asparagine, aspartic acid,
cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine.
Tyrosine is produced from phenylalanine, so if the diet is deficient in
phenylalanine, tyrosine will be required as well. The essential amino acids
(that we cannot produce internally) are arginine (required for the young, but
not for adults), histidine, isoleucine, leucine, lysine, methionine, phenylalanine,
threonine, tryptophan, and valine. These amino acids are required in the
diet. Plants, of course, must be able to make all the amino acids. Humans, on
the other hand, do not have all the the enzymes required for the biosynthesis
of all of the amino acids."
The
failure to obtain enough of even 1 of the 10 essential amino acids has
serious health implications and can result in degradation of the body's
proteins. Muscle and other protein structures may be dismantled to obtain the
one amino acid that is needed. "Unlike fat and starch, the human body
does not store excess amino acids for later useÑthe amino acids must be in
the food every day."(Biology Project)
|
Index
Biochemical concepts Chemistry concepts References Shipman, Wilson and Todd Ch 15 Tillery, Enger and Ross Ch 14  Biology Project University of Arizona |
||
|
This
is an explanation of what essential amino acids are and a list of the essential
amino acids for humans.
What Is an Essential Amino Acid?
An
essential amino acid may also be called
an indispensable amino acid. This is an amino acid that the body cannot
synthesize on its own, so it must be obtained from the diet. Because each has
its own physiology, the list of essential amino acids is different for humans
than it is for other organisms.
Essential Versus Conditionally
Essential Amino Acids
The
essential amino acids for all people are histidine, isoleucine, leucine,
lysine, methionine, phenylalanine, threonine, tryptophan and valine. Several
other amino acids are conditionally essential amino acids, meaning they are
required at some stages or growth or by some people who cannot synthesize them,
either because of genetics or a medical condition.
In
addition to the essential amino acids, babies and growing children also need
arginine, cysteine and tyrosine.
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Individuals
with phenylketonuria (PKU) need tyrosine and also must limit their intake of
phenylalanine. Certain populations need arginine, cystein, glycine, glutamine,
histidine, proline, serine and tyrosine because they either cannot synthesize
them at all or else are unable to make enough to meet the needs of their
metabolism.
Learn More About Amino Acids
List
of Essential Amino Acids
|
Essential
Amino Acids
|
Non-Essential
Amino Acids
|
|
Histidine
|
alanine
|
|
Isoleucine
|
arginine*
|
|
Leucine
|
aspartic
acid
|
|
Lysine
|
cysteine*
|
|
Methionine
|
glutamic
acid
|
|
Phenylalanine
|
glutamine*
|
|
Threonine
|
glycine*
|
|
Tryptophan
|
proline*
|
|
Valine
|
serine*
|
|
|
tyrosine*
|
|
|
asparagine*
|
|
|
selenocysteine
|
|
|
*conditionally
essential
|
Difference Between Essential & Non Essential Amino Acids
Animal-based
foods contain all essential amino acids.
Protein is part of
every cell in your body, as it builds and repairs tissues, including your skin
and muscles, and makes such vital substances as antibodies and insulin. Beyond
its fundamental roles, one of the most interesting things about protein is that
your body produces many thousands of different proteins from just 20 amino
acids. All 20 fill crucial roles, but they’re not all an essential part of your
diet.
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Amino Acid Basics
Amino acids can be used to produce energy, but their primary job is building proteins. Some amino acids also fill non-protein-building roles, such as forming neurotransmitters and hormones. The 20 amino acids have different chemical structures that dictate how they’re used. Each protein consists of 50 to 2,000 amino acids that are connected together in a specific sequence according to genetic instructions, notes the National Institute of General Medical Sciences. After the amino acids are linked, they’re folded and twisted into a unique shape, which determines the protein’s function. Amino acids fit into three categories: essential, nonessential and conditional.Essential Amino Acids
The essential amino acids, which are also referred to as indispensable, are the ones you must get through the foods you eat because your body can’t make them. Nine out of the 20 amino acids are essential, but adults only need to obtain eight of them: valine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and tryptophan. The ninth amino acid -- histidine -- is only essential for infants. Your body doesn’t store amino acids, so it needs a regular daily supply of these essential building blocks.Nonessential and Conditional
Nonessential is a slightly misleading label because these amino acids actually fill essential roles, but since they’re synthesized by your body, they’re not an essential part of your diet. Of the 11 nonessential amino acids, eight are called conditional amino acids. When you’re sick or under significant stress, your body may not be able to produce enough of these amino acids to meet your needs. The list of conditional amino acids includes arginine, glutamine, tyrosine, cysteine, glycine, proline, serine and ornithine. The remaining three -- alanine, asparagine and aspartate -- are nonessential.Dietary Requirements
You need a specific amount of each essential amino acid, but if you get your recommended daily allowance of total protein -- 46 grams daily for women and 56 grams for men -- and eat a variety of foods you should meet your amino acid requirements. Animal-based foods are called complete proteins because each serving contains all the essential amino acids. Plant-based foods -- except for soy and quinoa, which are complete plant proteins -- have too little of at least one essential amino acid, so they’re called incomplete proteins. Different types of incomplete proteins fill in each other's missing amino acids, so eating various grains, legumes and vegetables over the course of the day nets complete protein.
The 8 Essential Amino Acids
The
eight essential amino acids are valine, isoleucine, leucine,
phenylalanine, threonine, tryptophan, methionine, and lysine.
They
are called essential amino acids not because they are more important than other
amino acids but because it is essential that they are included in the daily
diet since they are not produced naturally by the body.
Valine
Valine,
apart from being an essential amino acid, is one of the three Branched-Chain
Amino Acids the other two being leucine and isoleucine. Foods rich
in valine include cottage cheese, fish, poultry, peanuts, sesame seeds and
lentils.
Together
with leucine and isoleucine, valine belongs to the group of proteinogenic amino
acids, building blocks of proteins that are produced by cells that are recorded
in the genetic code of each living thing.
Rich
sources of valine are tofu, egg white, nuts, beef, lamb and gelatin.
Role
of valine
Valine
is an important source of nitrogen, an important component in alanine and
glutamine synthesis in the muscles.
Isoleucine
Isoleucine is another Branched
Chain Amino Acids (BCAA). It cannot be produced in the body and thus should be
obtained from the food we eat, most of them you already have in your daily diet
such as eggs, chicken, fish, cheese, soy beans, seaweeds and turkey.
Research
studies show that isoleucine is an indispensable part of man's diet and that
lack of it can lead to serious negative nitrogen balance more seriously than
the experience with other amino acids.
Production
of isoleucine starts with pyruvic acid with the action of the enzymes valine
aminotransferase , acetohydroxy acid, isomeroreductase, dihydroxy acid
dihydratase, and acetolactate synthase.
Role
of isoleucine
- It regulates blood sugar and boosts the body's energy levels.
- It plays a key role in the transport of oxygen from the lungs to the various parts of the body and the production of hemoglobin, the part of the blood that contains iron.
- Isoleucine is important in the efficient metabolism of glucose as manifested by the increase in the absorption of sugar.
When
given orally, isoleucine reduces the level of sugar in the blood by 20 percent
and increases sugar absorption in the muscles by 71 percent without necessarily
increasing the level of insulin in the blood.
Leucine
Leucine
is
another Branched-Chain Amino Acids (BCAA). It is not produced naturally
by the body and has to be taken through the food we eat.
Leucine
is called a buffer protein because it has the ability to protect the body when
it lacks iron and at the same time provides protection the moment leucine
becomes poisonous to the body.
Leucine
is used to produce sterols, substances that resemble fats (popular example is
cholesterol) and are found in the liver, adipose and muscles tissues, but many
times more active in the muscle and adipose tissues.
It
is used as dietary supplement for body building and for enhancing physical
performance because it delays the deterioration of muscle tissues through the
significant increase in the production of muscle proteins.
It
is due to these characteristics that leucine is highly recommended as dietary
supplement for athletes and body builders to increase their stamina and
endurance. This also makes leucine an ideal dietary supplement for patients who
are recovering from major surgical procedures or those who were subjected to
serious trauma or extreme muscle pain.
An
overdose of leucine can lead to Maple Syrup Urine Disease (MSUD), a
disorder characterized by deficiency in keto hydrogenase complex that can cause
the accumulation of leucine, isoleucine and valine in the blood and urine. It
is called Maple Syrup Urine Disease because an infant suffering from MSUD has
urine that smells much like maple syrup, thus the name of the disease which can
cause delirium, neurologic disorders and death.
Role
of leucine in weight loss
- It can be used for losing weight because it has the ability to dissolve visceral fat, the kind of fat found in the deepest layer of the skin that does not respond to the usual weight loss exercises or non-surgical procedures.
Role
of leucine in the metabolism of protein during physical exertion and recovery
- Leucine is the branched chain amino acid that plays a major role in the production of proteins.
- Leucine is a great energy source especially during intense athletic performance and other extreme physical activities. It protects you from getting tired easily during exercise and it regulates your glucose level.
Phenylalanine
Phenylalanine
is a forerunner of tyrosine, the anti-depressant dopamine, norepinephrine,
epinephrine and the skin pigment, melanin. It is also a precursor of
phenylethylamine, a popular anti-depressant dietary supplement. It is naturally
present in mammalian breastmilk.
Eating
foods rich in phenylalanine will help prevent mood swings, help you out of
lethargy, sluggishness, feelings of low morale and anxiety.
There
are three forms of phenylalanine: L-phenylalanine, D-phenylalanine and
DL-phenylalanine.
L-phenylalanine
is converted to L-tyrosine, then to L-DOPA and to dopamine.
D-phenylalanine
produces endorphins which are released by the pituitary glands during exercise,
excitement, orgasm, when experiencing pain and after eating spicy food.
Compared
to L-phenylalanine, D-phenylalanine cannot efficiently cross the blood brain
barrier. D-phenylalanine is excreted in the urine without entering the central
nervous system.
DL-phenylalanine
is sold as a nutritional supplement to assert its analgesic and antidepressant
characteristics. Its ability to relieve pain can be attributed to the ability
of D-phenylalanine to block the enzyme carboxypeptidase to cause enkephalin
damage.
Role
of DL-phenylalanine in the body
DL-phenylalanine
relieves pain and fights depression. Its pain-relieving property can be
attributed to its ability to block the enzyme carboxypeptidase that causes
enkephalin damage.
Threonine
Threonine, like valine and
phenylalanine is not produced by the body, therefore it has to be taken through
the food we eat.
Threonine
is an important ingredient in the formation of bones and cartilages, hair teeth
and nails. The mucin content in threonine, serine and proline which account for
20% to 55% of the total amino acid content in the intestines is responsible for
this activity. This characteristic of threonine makes it a perfect ingredient
for most gel-like preparations and lubricants.
Threonine
can be found in abundance in cottage cheese, milk, eggs, sesame seeds, beans,
poultry, fish, meat, lentils, corn, and various grains.
Role
of threonine
- Threonine is responsible for the growth and development of liver muscles, skeletal muscles and small intestines of young animals.
- Threonine may also prevent cancer. This occurs during the process of phosphorylation which usually occurs on threonine, serine, and tyrosine residues.
Tryptophan
Tryptophan:
The sleep-inducing amino acid
Tryptophan is a sleep-inducing
amino acid which is an important component in the production of serotonin,
vitamin B3 or niacin, and auxin (a plant hormone).
It
is the tryptophan content found in milk, chocolates, oats, bananas, dried
dates, cottage cheese, turkey and peanuts that makes you sleep. This is
attributed to the high serotonin, (a neurotransmitter that calms the brain) and
high melatonin (a sleep-inducing hormone) levels in the brain when a
substantial amount of tryptophan-containing foods have been eaten.
The
"feel-good" hormone serotonin sets you in a good mood, stops
you from oversleeping and prevents you from feeling depressed. It is this
property of serotonin that makes it a popular treatment for anxiety and
depression.
Another
sleep-inducing hormone is melatonin which is produced in large
quantities when there is no sunlight. This explains why you are in a low mood,
feel sleepy and lethargic when there is no sunlight, and why, according to
statistics, so many people go into deep depression, some of them committing
suicide during wintertime.
Role
of tryptophan
In
low levels of serotonin in the brain
Tryptophan
is also used to treat seasonal affective disorder or SAD and premenstrual
disorder, diseases associated with low levels of serotonin in the brain.
Seasonal affective disorder is the term that refers to the winter blues
experienced by some people which manifests through extremely low levels of
serotonin and melatonin caused by the absence of sunlight during the gloomy
winter months.
In
the development of bladder cancer
Research
studies show that metabolites of tryptophan have something to do with the onset
and development of bladder cancer. The metabolites kynurenic acid,
acetyl-L-kynurenine, L-kynurenine, 3-hydroxy-L-kynurenine, and
3-hydroxyanthranilic acid were found in large quantity in the urine of urinary
bladder cancer patients.
Methionine
Methionine
Together
with cysteine, methionine is one of two sulfur-containing proteinogenic amino
acids. Methionine is important in the manufacture of cysteine, carnitine,
taurine, lecithin, phosphatidylcholine, and other phospholipids. Improper
conversion of methionine can lead to atherosclerosis.
Like
its sulfur-containing pair cysteine, methionine also serves as an effective
antioxidant and helps in body metabolism in the cellular level. It is a perfect
scavenging agent against oxidative stress due to its ability to be converted to
methionine sulfoxide. It is important because it can provide the body with the
sulfur and methyl elements essential for human growth.
Role
of methionine
- Methionine is used to treat diseases of the liver especially those caused by carbon tetrachloride and arsenic.
- Methionine is also known to possess the ability to minimize the spread of the flu virus by inhibiting their further proliferation in the body.
An
overdose of methionine increases acidity of urine and causes the elimination of
calcium from the body. This is the reason why this amino acid is given to dogs
as a dietary supplement to protect damage to plants by reducing the pH level of
the animal urine. Calcium supplementation is recommended to compensate for the
lost amount of calcium in the body.
This
amino acid is also used by plants for synthesis of ethylene. The process is
known as the Yang Cycle or the methionine cycle.
Methionine
and atherosclerosis
- Methionine can contribute to the development of atherosclerosis. Taking methionine beyond its allowable levels can increase the amount of fat in the blood and contribute in the accumulation of plaque in the arterial walls which is the main cause of atherosclerosis.
Excessive
methionine intake can also cause injury and damage to the endothelial cells
Lysine
Lysine, like the rest of
the essential amino acids, cannot be produced naturally by the body and must be
taken through dietary intake and supplements. It is one of the essential
building blocks of proteins.
Lysine
is a key component in the production of hormones and enzymes and plays an
important role in collagen production, a substance that is critical in bone,
muscle, cartilage, and skin formation.
Lysine
can be obtained by eating protein-rich foods like meat, fish, eggs, soybeans,
poultry products, nuts and other dairy products. This amino acid may be taken
as a supplement in the form of tablets, powder or injection.
Role
of lysine
- Lysine plays a key role in calcium absorption by reducing the amount of calcium being excreted in the urine.
- It promotes the growth of hair, nails, teeth and bones. It also prevents bone loss that leads to osteoporosis, though there's no evidence that lysine prevents osteoporosis.
- It also prevents the occurrence of herpes simplex infections, or cold sores, but again, further study has to be conducted to prove this claim.
Side
effects of lysine
Lysine
is considered safe except for a few cases of abdominal cramps and diarrhea when
taken in high doses. Patients suffering from cardiovascular diseases and those
under medications must consult with a physician or health practitioner before
taking lysine.
Lysine
should be taken by athletes who engage in strenuous physical activities for
stamina and endurance. Vegetarians need a bigger amount of lysine intake since
vegetables, except for legumes, contain very minimal amount of lysine.
Continuous
research is being conducted on the potential of lysine as an important
component in muscle-building, reducing cholesterol level and speeding up
recovery after surgery.
The 8 Essential Amino Acids
Although the body can produce many amino acids, it cannot synthesise these eight amino acids and they must be sourced from diet. They include: Phenylalanine, the three Branched Chain Amino Acids Valine, Leucine and Isoleucine, Lysine, Threonine, Tryptophan, and finally Methionine. Histidine is essential for infants, but not for adults.We have researched the top foods and most popular supplements for you on amazon.com.
Phenylalanine
Role
L-phenylalanine is an essential amino acid that is converted into another amino acid called tyrosine.
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This amino acid is
needed to form important
brain chemicals (neurotransmitters and hormones) including
norepinephrine (aka noradrenaline),
epinephrine (aka adrenaline), their
precursor L-dopa,
and finally thyroid hormones,
which are responsible for the regulation of our metabolism.
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