Arginine reduces the impact of the “slings and arrows of outrageous fortune”.
Arginine is a ‘semi-essential’ amino acid — which means that
it is produced in the body in limited amounts, but that an external
source is required during periods of maximal growth, severe
stress, and injury. The body uses it to make protein, nitric oxide,
creatine, and other polyamines.
Arginine plays many roles in the body and has significant effects on:
tissue growth, including muscle and bone
wound healing
energy metabolism
cardiovascular function, atherosclerosis
inflammation
immune function, response to infection
hormone secretion
insulin sensitivity
Some, but not all, of these physiologic effects result from arginine’s role as the sole source of the multifunctional messenger
molecule ‘nitric oxide’.
Arginine supplementation improves outcomes after infections,
wounds, burns, and other injuries, with no significant detrimental
effects. It stimulates the release of growth hormone, insulin,
and other hormones needed for tissue growth, immune response,
and the control of stress and inflammation.
Read L-Arginine Monograph
Dietary L-arginine is found in both plant and animal products; during the past two decades it has also become popular as a
dietary supplement.4
Arginine is a ‘semi-essential’ amino acid — which means that it is
produced in the body in limited amounts, but that an external source is
required during periods of maximal growth, severe stress, and injury.1 It serves as a precursor for protein, polyamine, creatine and nitric oxide biosynthesis.3
What we can’t tell you
In
the U.S. and some other industrialized countries, government agencies
like the U.S. Food and Drug Administration have adopted censorship as a
method for intensifying their control over the supplement industry and
its customers. Thus, FDA regulations prohibit us from telling you that
any of our products are effective as medical treatments, even if they are, in fact, effective.
Accordingly, we will limit our discussion of L-arginine to a brief summary of recent arginine research, and let you draw your
own conclusions about what medical conditions it may be effective in treating.
Arginine plays many roles in the body and has significant effects on:1,2
tissue growth, including muscle and bone
wound healing
energy metabolism
modulation of vascular tone and cardiovascular function
atherosclerosis
inflammation
immune function
response to infection
hormone secretion
insulin sensitivity
Some, but not all, of these physiologic effects result from arginine’s role as the sole source of the multifunctional messenger
molecule ‘nitric oxide’.2,3
Arginine supplementation improves outcomes in animals with infections, wounds, burns, and other injuries, with no significant
detrimental effects.1
It functions as a secretagogue, stimulating the release of growth
hormone, insulin-like growth factor type 1, insulin, and prolactin.
Arginine also stimulates T-cell and natural killer cell activity and
influences pro-inflammatory cytokine levels.3
Wound healing
Arginine enhances collagen deposition and tissue strength in artificial incisional wounds in rodents and humans. Arginine
supplementation has been proposed to normalize or enhance wound healing in humans.5
In
a randomized double-blind study of the effect of oral arginine
supplementation on wound healing and T-cell function in people more
than 65 years of age, forty-five elderly, healthy volunteers received
experimental wounds in one shoulder and in the upper thigh. Daily
supplements of 17 gm free arginine (in the form of arginine aspartate)
were given to thirty subjects for two weeks. The fifteen other wounded
subjects received a placebo syrup. The results suggested that arginine
supplementation improves wound healing and immune responses.8
Growth factors and muscle function
L-arginine
supplements have been popular for years as promoters of growth hormone
production in the human body. Clinical trials to test this idea
produced little more than confusion until it was realized that very
large doses (around 40 grams per day) are required when arginine is
used by itself.16
Dual
amino-acid supplementation with L-arginine and L-lysine, on the other
hand, increases growth hormone levels without the need for large doses
of either supplement. Studies using 1200-1500 mg of each supplement
showed that significant increases in growth hormone levels take place
in the blood from 30 to 90 minutes after consumption.12,13 It appears that the best time to take arginine+lysine is when one is resting — not when one is about to exercise. Exercise
itself causes growth hormone levels to rise, and this effect nullifies the advantage gained from the supplements.13
Muscle
function in the elderly typically declines, regardless of the amount of
exercise performed. Among the important causes of this decline are
deficiencies in the growth factor ‘IGF-1’ (insulin-like growth factor)
and the amino acid ‘cysteine’. Supplementation with arginine and
N-acetylcysteine (NAC) can correct these deficiencies. A clinical trial
in 2003 showed that the muscular response to physical exercise in frail
geriatric patients was ‘strongly enhanced’ by arginine+NAC
supplementation.14
IGF-1
is a key promoter of muscle growth in people of all ages — in fact, the
growth effects of growth hormone and of anabolic steroids like
testosterone may result from the induction of IGF-1 production in the
body rather than any direct effects on the muscles by these hormones
themselves. It is therefore of interest that the production of IGF-1 is
promoted directly by arginine at doses somewhat smaller than that
required to raise growth hormone concentrations. One study showed that
17 grams/day of arginine caused significant elevation of IGF-1 levels.8
Bone injuries and osteoporosis
In experiments with guinea-pigs, it was shown in 2004 that high-dose arginine supplements taken orally for 4 weeks accelerated
the healing of bone fractures and resulted in stronger bones.9
Experiments
have demonstrated that the amino acids arginine and lysine, used in
combination, stimulate the growth of bone cells and improve the
structure of collagen in osteoporotic bone tissue. Researchers
concluded that “administration of these amino acids may be useful in
clinical treatment and prevention of osteoporosis.”1718 When the medical world eventually gets around to studying the arginine+lysine combination as an osteoporosis therapy, smaller
dosages will undoubtedly be used — like those mentioned above in ‘Growth factors and muscle function’.
Arginine by itself does not work — a clinical trial using 14.8 g/day of L-arginine in postmenopausal women showed no prevention
of bone loss.
Cardiovascular effects
Arginine
is the body’s sole source of nitric oxide, a substance which serves as
a messenger in the blood and regulates vascular tone and blood
dynamics. It is therefore not surprising that arginine has effects on
processes that damage the cardiovascular system. Compelling evidence
shows that the administration of arginine reverses the damage to blood
vessels and heart that is associated with major cardiovascular risk
factors (high cholesterol, smoking, hypertension, diabetes, obesity,
insulin resistance, and aging) and ameliorates many cardiovascular
disorders, such as coronary and peripheral arterial disease, injuries
caused by blood clots, and heart failure.10,11
Immunity, surgical complications
Thirty
cancer patients undergoing major operations were studied in a clinical
trial of 25 g/day of arginine as an immune booster to prevent
post-surgical complications. Supplemental arginine significantly
enhanced immune responses, and the investigators concluded: “As a
nutrient substrate, arginine was nontoxic, and may benefit surgical
patients who are at increased risk of infection.”15
Conclusion
Are L-arginine supplements useful for the conditions and purposes mentioned above? We aren’t allowed to tell you, so you should
take a look at some of the references cited here, and then decide for yourself.
