Carnitine (L-carnitine): Weight loss and Boost Exercise Performance Supplement
Demystified
Carnitine is a substance that helps the body turn fat into energy. Your body
makes it in the liver and kidneys and stores it in the skeletal muscles, heart,
brain, and sperm.
Usually, your body can make all the carnitine it needs. Some people, however,
may not have enough carnitine because their bodies cannot make enough or can�t
transport it into tissues so it can be used. Some other conditions, such as
angina or intermittent claudication, can also cause low levels of carnitine in
the body, as can some medications.
Carnitine has been proposed as a treatment for many conditions because it acts
as an antioxidant. Antioxidants fight harmful particles in the body known as
free radicals, which damage cells and tamper with DNA. Antioxidants can
neutralize free radicals and may reduce or help prevent some of the damage they
cause.
Some of the conditions carnitine may help treat are serious. Serious diseases
and conditions require conventional medical treatment, and you should talk to
your health care provider before taking carnitine. For other conditions, such as
fatigue or improving athletic performance, carnitine seems safe but may not help
much.
L-Carnitine is touted to be a fat-burning agent, as a carnitine-dependent enzyme
(carnitine palmitoyltransferase) is the rate-limiting step of transporting fatty
acids into the mitochondria for their subsequent oxidation (the �burning� of the
fat). Beyond that, carnitine is also said to enhance recovery from exercise.
L-Carnitine provision does not inherently increase the rate of fatty-acid
oxidation, although it seems to under a few instances. For those deficient in
carnitine, usually elderly individuals (65+) and vegetarians, supplementation
can help burn fat. In otherwise healthy and young omnivores, carnitine has not
been demonstrated to have fat-burning properties. Preloading exercise with
carnitine supplements (either tartrate or GPLC) does appear to have a
muscle-protection effect, as increases of biomarkers of damage measured the next
day appear to be reduced. Carnitine does not appear to have 100% reliability in
actually increasing performance, although it has been associated with it at some
times, and although this could lead to increased muscle mass over time (by
allowing more work to be conducted) this has not yet been shown with carnitine
supplements.
A variant of carnitine known as Acetyl-L-Carnitine (ALCAR) is commonly used in
nootropic communities for its cognition-enhancing effects, which are said to be
stimulatory but �cleaner� than caffeine. This may be related to an increase in
neural glucose consumption, and would be an added benefit for elderly persons
who might be partially deficient.
L-carnitine is an amino acid (a building block for proteins) that is naturally
produced in the body. L-carnitine supplements are used to increase L-carnitine
levels in people whose natural level of L-carnitine is too low because they have
a genetic disorder, are taking certain drugs (valproic acid for seizures), or
because they are undergoing a medical procedure (hemodialysis for kidney
disease) that uses up the body�s L-carnitine. It is also used as a replacement
supplement in strict vegetarians, dieters, and low-weight or
premature infants.
L-carnitine is used for conditions of the heart and blood vessels including
heart-related chest pain, congestive heart failure (CHF), heart complications of
a disease called diphtheria, heart attack, leg pain caused by circulation
problems (intermittent claudication), and high cholesterol.
Some people use L-carnitine for muscle disorders associated with certain AIDS
medications, difficulty fathering a child (male infertility), a brain
development disorder called Rett syndrome, anorexia, chronic fatigue syndrome,
diabetes, overactive thyroid, attention deficit-hyperactivity disorder (ADHD),
leg ulcers, Lyme disease, and to improve athletic performance and endurance.
The body can convert L-carnitine to other amino acids called acetyl-L-carnitine
and propionyl-L-carnitine. But, no one knows whether the benefits of carnitines
are interchangeable. Until more is known, don�t substitute one form of carnitine
for another.
L-carnitine helps the body produce energy. It is important for heart and brain
function, muscle movement, and many other body processes.
Heart Conditions
Angina -- Some good evidence shows that carnitine can be used along with
conventional treatment for stable angina. Several clinical trials show that L-carnitine
and propionyl-L-carnitine can help reduce symptoms of angina and improve the
ability of people with angina to exercise without chest pain. Do not self-treat
chest pain with carnitine, however. See your healthcare provider for diagnosis
and conventional treatment, and take carnitine only under your health care
provider's supervision.
Heart attack -- A few studies have found that carnitine may help when
used with conventional medicines after a heart attack, but not all studies
agree. Some small studies suggest that people who take L-carnitine supplements
soon after a heart attack may be less likely to have another heart attack, die
of heart disease, have chest pain and abnormal heart rhythms, or develop heart
failure. However, other studies have shown no benefit. Treatment with oral
carnitine may also improve muscle weakness. Carnitine should be used along with
conventional medication under your health care provider supervision.
Heart failure -- A few small studies have suggested that carnitine
(usually propionyl-L-carnitine) can help reduce symptoms of heart failure and
improve exercise capacity in people with heart failure. However, more and larger
studies are needed to know for sure.
Peripheral Vascular Disease
Decreased blood flow to the legs from atherosclerosis or hardening of the
arteries -- where plaque builds up in the arteries -- often causes an aching or
cramping pain in the legs while walking or exercising. This pain is called
intermittent claudication, and the reduced blood flow to the legs is called
peripheral vascular disease (PVD). Several studies show that carnitine can help
reduce symptoms and increase the distance that people with intermittent
claudication can walk. Most studies have used propionyl-L-carnitine. Scientists
don't know whether L-carnitine would work the same.
Diabetic Neuropathy
Diabetic neuropathy happens when high blood sugar levels damage nerves in the
body, especially the arms, legs, and feet, causing pain and numbness. Some small
preliminary studies suggest acetyl-L-carnitine may help reduce pain and increase
feeling in affected nerves. It is also possible that carnitine can help nerves
regenerate. More research is needed.
Exercise Performance
Although carnitine is often taken to boost exercise performance, there is no
evidence it works.
Weight Loss
Although L-carnitine has been marketed as a weight loss supplement, there is no
scientific evidence to show that it works. Some studies do show that oral
carnitine reduces fat mass, increases muscle mass, and reduces fatigue, which
may contribute to weight loss in some people.
Alzheimer's Disease and Memory Impairment
The evidence is mixed as to whether carnitine is useful in treating Alzheimer's
disease. Several early studies showed that acetyl-L-carnitine, might help slow
down the progression of Alzheimer's disease, relieve depression related to
senility and other forms of dementia, and improve memory in the elderly. But
larger and better-designed studies found it didn�t help at all. People should
take carnitine for Alzheimer's and other forms of dementia only under the
supervision of their health care provider.
Kidney Disease and Dialysis
Because the kidneys make carnitine, kidney disease could lead to low levels of
carnitine in the body. If you have kidney disease, your health care provider may
prescribe carnitine but you shouldn�t take it without medical supervision.
Male Infertility
Low sperm counts have been linked to low carnitine levels in men. Several
studies suggest that L-carnitine supplements may increase sperm count and
mobility.
Erectile Dysfunction Preliminary studies suggest propionyl-L-carnitine may help
improve male sexual function. One study found that carnitine improved the
effectiveness of sidenafil (Viagra) in men with diabetes who had not previously
responded to Viagra. In another study, a combination of propionyl-L-carnitine
and acetyl-L-carnitine improved the effectiveness of Viagra in men who had
erectile dysfunction after prostate surgery. More studies are needed.
Peyronie's Disease
Peyronie's disease is characterized by a curvature of the penis that leads to
pain during an erection. One promising study compared acetyl-L-carnitine to the
medication tamoxifen in 48 men with this condition. Acetyl-L-carnitine worked
better than tamoxifen at reducing pain during sex and reducing the curve of the
penis. Acetyl-L-carnitine also had fewer side effects than tamoxifen. More
research is needed.
Hyperthyroidism
Some research suggests that L-carnitine may help prevent or reduce symptoms of
an overactive thyroid, such as insomnia, nervousness, heart palpitations, and
tremors. In fact, in one study, a small group of people with hyperthyroidism saw
these symptoms improve, and their body temperature become normal, when taking
carnitine. But a larger, better-designed clinical trial is needed to see if
carnitine really works. In addition, researchers think carnitine may work by
blocking the action of thyroid hormone, which could be dangerous for people with
low thyroid levels. Don�t take carnitine for hyperthyroidism without your
doctor�s supervision.
Dietary Sources
Red meat (particularly lamb) and dairy products are the main food sources of
carnitine. It can also be found in fish, poultry, tempeh, wheat, asparagus,
avocados, and peanut butter.
Carnitine is available as a supplement in a variety of forms.
L-carnitine: the most widely available and least expensive
Acetyl-L-carnitine: Often used in studies for Alzheimer's disease and
other brain disorders
Propionyl-L-carnitine: Often used in studies for heart disease and
peripheral vascular disease
Avoid D-carnitine supplements. They interfere with the natural form of
L-carnitine and may produce unwanted side effects.
In some cases, L-carnitine may be taken by prescription or given
intravenously by a health care provider.
How to Take It
Pediatric
Don�t give carnitine supplements to a child without your child's health care
provider's supervision. Your child's health care provider should first make sure
that the child has a carnitine deficiency.
Adult
Recommended doses of L-carnitine vary depending on the health condition being
treated. The usual dose is between 1 - 3 g per day.
Precautions
Because supplements may have side effects or interact with medications, you
should take them only under the supervision of a knowledgeable healthcare
provider. Side effects are generally mild. High doses (5 or more grams per day)
may cause diarrhea. Other rare side effects include increased appetite, body
odor, and rash.
People with the following conditions should talk to their health care provider
before taking carnitine:
Peripheral vascular disease
High blood pressure
Liver disease from alcoholism (cirrhosis)
Diabetes
Kidney disease
History of seizures
Possible Interactions
If you are being treated with any of the following medications, you should not
use carnitine without first talking to your healthcare provider. AZT -- In a
laboratory study, L-carnitine supplements protected muscle tissue against toxic
side effects from AZT, a medication used to treat HIV and AIDS. More studies are
needed to know whether L-carnitine would have the same effect in people.
Doxorubicin -- Treatment with L-carnitine may protect heart cells against
the toxic side effects of doxorubicin, a chemotherapy medication used to treat
cancer, without making the medication any less effective. Always talk to your
oncologist before using any complementary or alternative therapy with
chemotherapy.
Isotretinoin (Accutane) -- Accutane, a strong medication used for severe
acne, can cause liver problems, as measured by a blood test, as well as high
cholesterol and muscle pain and weakness. These symptoms are like those seen
with carnitine deficiency. Researchers in Greece showed that a large group of
people who had side effects from Accutane got better when taking L-carnitine
compared to those who took a placebo.
Thyroid hormone -- Carnitine may stop thyroid hormone from getting into
cells, and theoretically may make thyroid hormone replacement less effective. If
you take thyroid replacement hormone, talk to your health care provider before
taking carnitine.
Valproic acid (Depakote) -- The anti-seizure medication valproic acid may
lower blood levels of carnitine. Taking L-carnitine supplements may prevent any
deficiency and may also reduce the side effects of valproic acid. However,
taking carnitine may increase the risk of seizures in people with a history of
seizures.
Products containing L-carnitine can now be marketed as "natural health products"
in Canada. As of 2012, Parliament has allowed carnitine products and supplements
to be imported into Canada (Health Canada). The Canadian government did issue an
amendment in December 2011 allowing the sale of L-carnitine without a
prescription.
The highest concentrations of carnitine are found in red meat. Carnitine can be
found at significantly lower levels in many other foods including nuts and seeds
(e.g. pumpkin, sunflower, sesame), legumes or pulses (beans, peas, lentils,
peanuts), vegetables (artichokes, asparagus, beet greens (young leaves of the
beetroot), broccoli, brussels sprouts, collard greens, garlic, mustard greens,
okra, parsley, kale), fruits (apricots, bananas), cereals (buckwheat, corn,
millet, oatmeal, rice bran, rye, whole wheat, wheat bran, wheat germ) and other
foods (bee pollen, brewer's yeast, carob).
In the course of human aging, carnitine concentration in cells diminishes,
affecting fatty acid metabolism in various tissues. Particularly adversely
affected are bones, which require continuous reconstructive and metabolic
functions of osteoblasts for maintenance of bone mass. A 2008 study found that
supplementing with L-carnitine decreased bone turnover and increased bone
mineral density in rats.
Effect on thyroid hormone action
A 2004 study found that L-carnitine acts as a peripheral antagonist of thyroid
hormone action. In particular, L-carnitine inhibits both triiodothyronine (T3)
and thyroxine (T4) entry into the cell nuclei. For this reason, L-carnitine has
been proposed as a supplement to treat hyperthyroidism. A 2001 study found that
L-carnitine was useful in both reversing and preventing hyperthyroid symptoms.
Possible health effects
Carnitine has been proposed as a supplement to treat a variety of health
conditions including heart attack, heart failure, angina, narcolepsy, and
diabetic neuropathy, but not fatigue, improving exercise performance, nor
wasting syndrome (weight loss). In all of these cases, both positive and
negative findings, the results are preliminary, proposed, and not part of
routine treatment.
There is also some suggestion that use of acetyl carnitine and L-arginine may
improve sperm motility in men with sperm abnormalities.
Angina -- Some good evidence shows that carnitine can be used along with
conventional treatment for stable angina. Several clinical trials show that L-carnitine
and propionyl-L-carnitine can help reduce symptoms of angina and improve the
ability of people with angina to exercise without chest pain. Do not self-treat
chest pain with carnitine, however. See your healthcare provider for diagnosis
and conventional treatment, and take carnitine only under your health care
provider's supervision.
The evidence is mixed as to whether carnitine is useful in treating Alzheimer's
disease. Several early studies showed that acetyl-L-carnitine, might help slow
down the progression of Alzheimer's disease, relieve depression related to
senility and other forms of dementia, and improve memory in the elderly. But
larger and better-designed studies found it didn�t help at all. People should
take carnitine for Alzheimer's and other forms of dementia only under the
supervision of their health care provider.
Peripheral vascular disease