Monday, August 3, 2009
What is it? Arginine is a conditionally essential amino acid. It’s an essential amino acid in infancy/early childhood, and under stress conditions where the body cannot manufacture cient l-arginine to meet increased demand. Beyond its role in protein synthesis, arginine is a precursor for a number of important metabolites, including creatine and nitric oxide. It is an im- portant intermediate in the urea cycle, and can stimulate the secretion of growth hormone.
What is it supposed to do?
The current interest in arginine and related compounds such as arginine-
alpha-ketoglutarate (AAKG) lies in its role in the production of nitric oxide.
NO is the new superstar molecule with researchers as it appears to play a
role directly or indirectly in almost every aspect of human physiology, such
as the immune system, nervous system, circulatory system, and many oth-
Arginine is a key component of the NO production pathway (arginine
serves as the substrates for the nitric oxide synthase enzyme, which pro-
duces citrulline and NO from arginine) which is essential for a cascade of
reactions involved in vasodilation and cardiovascular function.
Supplements containing arginine/AAKG are supposed to enhance the pro-
duction of NO, and increase the “pump” you get during a hard workout in
What does the research say?
Recent data suggest arginine may have some legitimate uses regarding
health and well being. For example, the lining of artery walls called the
endothelium needs to dilate and contract e ectively.
NO is essential to this function and several studies have found arginine
supplements at 8 - 20 grams per day restored endothelial vasodilation in
the coronary arteries and may improves overall blood ow, which is impor-
tant for people su ering from ischemic issues.
Another study suggested that arginine supplementation greatly improved
penile function in men with penile dysfunction as NO is essential for blood
ow involved in getting an erection.
Arginine has shown a very good safety pro le to date and appears to have
virtually no toxic Effects . From an athletic/muscle building point of view,
things become much less clear. Early studies suggested arginine could in-
crease growth hormone levels, but in truth (a) these Effects were found us-
ing very high doses and were intravenous and (b) short lived spikes in GH
don’t appear to have any positive Effects on muscle mass or performance
in healthy athletes anyway.
NO is a messenger molecule related to virtually every pathway in the hu-
man body, one way or another. Therefore, simply raising NO will have both
positive and negative Effects , most of which are not known at this time.
Having chronically elevated levels of NO above normal may not be a good
idea. For example, though NO is associated with some potentially positive
Effects mentioned above, elevated NO levels are also associated with some
negative Effects . High levels of NO are associated with increased levels of
an extremely powerful pro-oxidant called peroxynitrate, which immune
cells use to kill pathogens. High levels of peroxynitrate may lead to greater
oxidative stress, immune disorders, and increased in ammation. For exam-
ple, high levels of NO and peroxynitrate are associated with bromyalgia,
chronic fatigue, and multiple chemical sensitivity. Therefore, it might not
be a wise idea to have chronically elevated levels, especially if you have any
of the aforementioned syndromes.
What does the real world have to say?
A decade ago, arginine had a brief day in the limelight with athletes as a
supplement that might stimulate growth hormone. However, its use as a
GH releaser never materialized into new muscles for users, so it quickly fell
out of favor.
Recently, however, there has been a resurgence of interest in arginine by
athletes and supplement companies. This is due to recent ndings show-
ing a long list of possible uses with arginine, ranging from possible protec
tion from heart disease, reducing cholesterol, to increasing blood ow.
This brings us to the new supplements known as “hemodilators” that claim
to give you a “perpetual pump” and other marketing buzz words based on
elevated NO. These new products are based on a form of arginine called Ar-
ginine Alpha-Ketoglutarate, which is simply arginine bound to alpha keto
glutarate (AKG), a supplement that had a short life some years ago. Some
of these new supplements claim some form of time delay or extended re-
lease to keep NO elevated.
There are many problems with the above, some of which I have mentioned
already. For one thing, there are no data to show such products keep NO
elevated all day, there may be medical and physiological reasons to avoid
constantly elevated levels of NO, and there are no studies at all showing
such products increase LBM. In fact, there’s even been one study that
demonstrates that NO supplements are worthless for increasing LBM. One
study, sponsored by an NO supplement manufacturer, concluded:
“AAKG supplementation appeared to be safe and well tolerated, and positively
in uenced 1RM bench press and Wingate peak power performance. AAKG did
not in uence body composition or aerobic capacity.”
To say that supplement manufacturers are overstating the muscle building
Effects of these new (and they are not really new, but are just being repack-
aged as new) products is being kind…
Interestingly, while some improvements in performance were seen in the
above study, these may well be due to the age of the subjects being tested
in both studies: 30 - 50 year old men. Middle-aged men are more likely to
have some markers of cardiovascular disease, such as elevated homocys-
teine and asymmetrical dimethylarginine (ADMA) levels. ADMA is a com-
petitive inhibitor of nitric oxide synthase (NOS), which is the enzyme re-
sponsible for NO production. So positive performance results in this group
may be due to a reduction in ADMA inhibition of NOS, rather than to the
increased availability of arginine for NO production. Under normal con-
ditions, arginine is not limiting for NO production, so increasing arginine
should not result in increased NO production.