Acetyl-L-Carnitine Supplements Review
Choose the Best
Acetyl-L-Carnitine Supplement. Don't Overpay! CL Identifies Quality
Acetyl-L-Carnitine Supplements at the Best Value.
Medically reviewed and
edited by Tod Cooperman, M.D. 
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Table of Contents
Update
Update:
Vitacost Acetyl-L-Carnitine HCl
500 mg (4/1/16, Updated 4/5/16): A CL member reported recently
purchasing this product on Amazon.com (where it is listed as "from Vitacost Brand") but, upon opening the sealed
container, noticed, that "the capsules are two different colors. About
half are a solid light cream color. The other half have light tan spots all
over the capsule." See Photo. Despite the
odd appearance, a family member used the product for four days. No adverse
effects were reported. The product is marked Lot # 503872, Exp date - 4/18.
When ConsumerLab.com tested this product in 2012 for its Review (below), all
capsules had a uniform whitish color -- none had spots. The spots are not
normal. It would appear that there is a problem with the production of this
product. We speculate that some of the capsules may have been exposed to
conditions which oxidized certain components. If you have purchased a similar
product, we suggest that you do not use it.
We asked Vitacost for a response and received the
following on 4/5/16: "A little background on the product: Carnitine is
a very unstable molecule, especially in its base form. Acetyl-L Carnitine is
more stable, but it is very sensitive to moisture and temperature. If bottles
are not closed tightly, they will easily oxidize, a process that may result in
spots. It's important to note that although it may be unsightly, spotting does
not necessarily means that the product is bad or that
it has lost its efficacy. We have checked multiple samples of lot you
referenced and are not seeing oxidation or any other color inconsistencies."
"Because items on Amazon are not being sold directly through us, we
unfortunately cannot guarantee the product was stored properly in the seller's
possession. Vitacost distribution centers are
temperature and moisture controlled and we recommend that your member purchase
this product from us directly in the future. Once you receive your Acetyl-L
Carnitine, it should be stored in a cool, dry place (we don't recommend storing
it in a bathroom because of the heat and moisture) and kept tightly sealed.
That being said, we stand behind all of our Vitacost
brand products, and our policy is that we'll buy it back if you're not
satisfied for any reason - even if the bottle or bag is empty. If your member
is a customer of Vitacost we can offer them a full
refund. If not, we are more than happy to send a replacement bottle at no
charge!"
Since originally posting this update, another CL member notified us of the same
problem with the same product bearing the same lot number and expiration date,
suppling us with photographic evidence and noting that some of the product had
been used without harm. This time, however, the product had been purchased
directly from Vitacost (which has provided a full
refund). We have asked Vitacost to comment on this
second report, particulary as the product was
purchased from Vitacost and not a third party, and to
explain why only some of the capsules are spotted. We were told that a response
will be provided this week, and we will post the response here. [No response
was received from Vitacost.]
Problems with products can be reported to ConsumerLab.com at www.ConsumerLab.com/SupplementProblemReport.asp.
What It Is:
Acetyl-L-carnitine is a
particular form of carnitine, a non-essential amino acid that can be
synthesized in the body from lysine and methionine and is found in red meats
and dairy products. It is believed that acetyl-L-carnitine plays a role in
production of acetylcholine, an important neurotransmitter.
What It Does:
Acetyl-L-carnitine
is one of many dietary supplement ingredients that have been evaluated to help
prevent or treat memory disorders. Other ingredients tested and
reviewed by ConsumerLab.com include ginkgo, huperzine A, ginseng, niacinamide, and fish/marine oils. While early studies found
evidence of modest benefit with acetyl-L-carnitine in Alzheimer's disease and
other forms of dementia, later, larger studies failed to find it effective (Hudson, Cochrane Database Syst Rev 2003). If
there is any benefit at all, it may be limited to people with mild cognitive
impairment and early Alzheimer's disease (Montgomery, Int Clin Psychopharmacol,
2003).
Acetyl-L-carnitine seems to improve symptoms of diabetic
neuropathy and neuropathy associated with antiretroviral drug
therapy used by people with HIV infection. It also may reduce pain and
improve mental health in people with fibromyalgia.
Taking acetyl-L-carnitine in combination with
propionyl-L-carnitine seems to help symptoms of androgen decline in
older men, improving sexual dysfunction, depression,
and fatigue. It may also improve memory in chronic
alcoholics and increase sperm motility in men with
infertility. Acetyl-L-carnitine may be helpful in an inflammatory condition of
the penis called Peyronie's disease,
where it has been shown to reduce pain and slow progression of the disease (Biagiotti, BJU Int. 2001). Early research
suggests that acetyl-L-carnitine might reduce hyperactivity in
boys with fragile X syndrome.
Acetyl-L-carnitine (500 to 1,000 mg) taken twice
daily for a period of months may modestly reduce systolic blood
pressure in people with high blood pressure, although it does not
seem to lower diastolic blood pressure. One study found that
taking 1 gram of acetyl-L-carnitine twice daily for 6 months lowered systolic
blood pressure by about 8 mm Hg compared to baseline, although this study did
not have a comparison group so the results are uncertain (Ruggenenti,
Hypertension 2009). Another study in 36 people (average age
63) with coronary artery disease found that taking 500 mg of acetyl-L-carnitine
plus 200 mg of alpha-lipoic acid twice daily for 8 weeks lowered
systolic blood pressure by 9 mm Hg in people with coronary artery disease and high
blood pressure, which was significant compared to placebo. The study was
partially funded by the maker of the supplement (Juvenon
Cellular Health Supplement, Juvenon Inc.) (McMackin, J Clin Hypertens 2007).
Although a study in 219 older people with high blood pressure, high cholesterol
and diabetes found that taking 1 gram of acetyl-L-carnitine twice daily for 6
months did not lower systolic blood pressure compared to
placebo, the people in this study were taking the cholesterol-lowering medicine
simvastatin, which can also lower blood pressure and may have overshadowed any
effects of acetyl-L-carnitine (Parvanova, J Endocr Soc 2018).
Some studies with L-carnitine (not acetyl-L-carnitine) have evaluated its
potential use in weight loss because L-carnitine is involved
in the transport of fatty acids into the mitochondria of cells for use as fuel.
However, a weight loss benefit has not been demonstrated. A study in which
moderately obese women were given 2 grams daily of L-carnitine for eight weeks
showed no effect on amounts of body fat or body weight (Villani, Int J Sport Nutr Excerc Metab 2000).
Quality Concerns and
Tests Performed:
Neither
the U.S. government nor any other agency is responsible for routinely testing
dietary supplements for their contents or quality. In order to help consumers identify products of better quality,
ConsumerLab.com purchased and tested acetyl-L-carnitine supplements for the
quality of their ingredients and other relevant parameters as described below.
See Testing Method for
more details.
Because carnitine is sold in different chemical forms that may have different
effects, CL specifically tested for acetyl-l-carnitine, the form most studied
for memory enhancement. Any product in tablet form (excluding chewable and
time-release tablets) was tested for its ability to properly break apart
(disintegrate) in solution — which is necessary for ingredients to be
absorbed.
What CL Found:
All three of the
acetyl-L-carnitine supplements selected for review by ConsumerLab.com passed
testing (Bluebonnet, Doctor's Best, and Jarrow
Formulas) as did four other products (GNC, Twinlab, Vitacost (see Update), and Vitamin Shoppe) tested
through CL's Voluntary Certification Program.
As acetyl-L-carnitine supplements are among the more expensive supplements and
the products essentially contain the same key ingredient in a capsule, it pays
to comparison shop for the lowest cost while factoring in other special
requirements you may have, such as having a product that is gluten free,
kosher, etc. The cost to obtain a 1,500 mg dose of acetyl-L-carnitine from the
reviewed products ranged from a low of 30 cents from Vitacost (which
is gluten-free) (see Update) to a high of $1.24 from Bluebonnet (which
is gluten-free as well as vegetarian and kosher).
Test Results by Product:
Listed
below are the test results for seven different acetyl-Lcarnitine
supplements, listed alphabetically. ConsumerLab.com selected three products.
Three other products (each indicated with an asterisk) were tested at the
request of their manufacturers/distributors through CL's Voluntary Certification
Program and are included for having passed testing.
Shown for each product is the claimed amount and form of the tested ingredient
and the serving size recommended on the label. The full list of ingredients is
available for each product by clicking on the word "Ingredients" in
the first column. Products listed as "Approved" met their label
claims and ConsumerLab.com's quality criteria (see Passing Score). Be aware
that suggested serving sizes on labels may not reflect an appropriate dosage
for your intended use. Be sure to compare the "Suggested Daily
Serving" in the second column to dose information provided in What to Consider When Using. Cost comparisons
are shown in the last column.
|
CONSUMERLAB.COM RESULTS FOR ACETYL-L-CARNITINE SUPPLEMENTS |
|||||
|
Product Name, Unit
Type, and Suggested Daily Serving |
Amount of
Acetyl-L-Carnitine Per Suggested Daily Serving on Label |
--TEST RESULTS -- |
|||
|
OVERALL RESULTS: |
Met Claim |
Broke Apart Properly |
Cost for 1,500 mg
Acetyl-L-Carnitine1 |
||
|
Acetyl-L-Carnitine Supplements: |
|||||
|
Bluebonnet Acetyl-L-Carnitine 500 mg |
500 mg |
APPROVED |
|
N/A |
$1.24 |
|
Doctor's Best® Best
Acetyl-L-Carnitine |
500 to 2,000 mg |
APPROVED |
|
N/A |
$0.55 |
|
GNC Acetyl L-Carnitine 500 |
500 to 1,000 mg |
APPROVED |
|
N/A |
$0.87 |
|
Jarrow Formulas® Acetyl L-Carnitine 500 |
500 to 1,000 mg |
APPROVED |
|
|
$0.52 |
|
Twinlab® Acetyl-L-Carnitine |
500 to 2,000 mg |
APPROVED |
|
N/A |
$0.75 |
|
Vitacost® Acetyl-L-Carnitine HCl 500 mg |
500 mg |
APPROVED |
|
N/A |
$0.30 |
|
Vitamin Shoppe® Acetyl-L-Carnitine 500 mg |
500 mg |
APPROVED |
|
N/A |
$0.87 |
|
Not applicable: Only non-chewable, non-capsule,
non-enteric coated, and non-time release formulations are tested for
disintegration. |
|||||
|
Unless otherwise noted, information about the products
listed above is based on the samples purchased by ConsumerLab.com (CL) for
this Product Review. Manufacturers may change ingredients and label
information at any time, so be sure to check labels carefully when evaluating
the products you use or buy. If a product's
ingredients differ from what is listed above, it may not necessarily be of the
same quality as what was tested. |
|||||
|
Copyright ConsumerLab.com, LLC, 2012 All rights reserved.
Not to be reproduced, excerpted, or cited in any fashion without the express
written permission of ConsumerLab.com LLC |
|||||
ConsumerTips™:
What to Consider When
Buying:
Different forms of carnitine are used for different purposes.
Acetyl-L-carnitine is somewhat different from both L-carnitine and
propionyl-L-carnitine. Although the body can convert L-carnitine to
acetyl-L-carnitine and vice versa, it is not known whether the benefits of
acetyl-L-carnitine are from the intact molecule, from its metabolites, or some
other activated form, so it is advisable not to substitute one form of
carnitine for another. Another form of carnitine, D-carnitine, should not be
used as it may compete with other forms of carnitine and cause symptoms of
carnitine deficiency.
What to Consider When Using:
Acetyl-L-carnitine is taken in fairly large doses - often measured in grams
rather than milligrams (1,000 mg = 1 gram). In Alzheimer's disease, 1.5 to 4
grams daily has been used, usually divided into two or three doses during the
day. In age-related memory impairment, 1.5 to 2 g daily has been used. For
depression in the elderly, 1.5 to 3 grams daily in divided doses has been used.
For diabetic neuropathy, 1.5 to 3 grams per day in divided doses has been used,
with the higher dose apparently more effective for improving vibratory
sensations and reducing neuropathy-related pain. For neuropathy associated with
antiretroviral drug therapy, the dose is 1 gram two times daily. The dose for
reducing fibromyalgia pain is 1.5 grams each day.
In infertile men, 3 to 4 grams daily has been used to improve sperm function,
sometimes as a mixture of acetyl-L-carnitine and L-carnitine. For Peyronie's disease, 2 grams divided into two doses during
the day for 3 months has been used. For symptoms of age-related testosterone
deficiency, 2 grams of acetyl-L-carnitine plus 2 grams of propionyl-L-carnitine
daily have been used. For boys with fragile X syndrome, the daily dose to
reduce hyperactivity is 20 to 50 mg/kg.
Concerns and Cautions:
Alzheimer's disease and other types of severe
age-related mental impairment are too serious to treat on your own and the
symptoms of these diseases could be confused with those of other serious
conditions. It is advisable to see your doctor before self-medicating for
severe memory or cognitive problems. Acetyl-L-carnitine is believed to be quite
safe, but may cause gastrointestinal side-effects and agitation. It can also
cause the urine, breath and sweat to have a fishy odor. Acetyl-L-carnitine
should be used with caution in people taking blood-thinning medication, as it
can theoretically increase the anti-coagulant effect. People with low or
borderline-low thyroid levels should not take acetyl-L-carnitine or other forms
of carnitine because it may impair thyroid hormone function. Low thyroid levels
are particularly common among women over 60 years of age. (Conversely, in cases
of hyperthyroidism giving acetyl-L-carnitine or other forms of
carnitine may be helpful.) (Benvenga, Ann NY Acad Sci 2004).
Individuals on dialysis should not take this without a physician's supervision
when used orally and appropriately.
L-carnitine
Although acetyl-L-carnitine is not the same as L-carnitine, it contains (and
provides) L-carnitine, so it is worth noting the following concerns with
L-carnitine:
Some research suggests that L-carnitine intake may contribute
to cardiovascular disease in certain people. People who eat red meat (e.g.,
beef) maintain organisms in their gut which digest carnitine to the compound
TMA, which is then converted in the liver to the compound TMAO, which appears
to advance atherosclerosis (hardening of the arteries) by reducing the normal
clearing of cholesterol (Koeth, Nature Medicine 2013). Vegetarians and vegans do
not have this reaction when first exposed to carnitine. Supplementing with
L-carnitine (and possibly acetyl-L-carnitine due to their chemical similarity,
i.e., both contain the TMA moiety) may potentially foster growth of these
organisms, increase levels of TMAO, and have negative long-term cardiovascular
effects. However, a study among healthy, active older women found no
significant increase in blood-based markers thought to predict future
cardiovascular events when they were given 1,020 mg of L-carnitine (from 1,500
mg of L-carnitine-L-tartrate) for 24 weeks even though their blood levels of
TMAO increased ten-fold (Samulak, Ann Nutr Metab 2018).
Also, L-carnitine may worsen
chemotherapy-related nerve damage: A double-blind, placebo-controlled study
among women receiving taxane-based chemotherapy to
treat breast cancer found that 3 grams of L-carnitine taken daily for 5 ˝
months significantly worsened symptoms of chemotherapy-induced peripheral
neuropathy compared to placebo, and this difference was also seen after 2
years. The effect was unexpected, although a similar problem has been observed
with other antioxidants given during chemotherapy (Hershman, J Clin Oncol 2018). Based on this evidence, the American Society of
Clinical Oncology recommended in 2020 that clinicians discourage use
of acetyl-L-carnitine for preventing chemotherapy-related nerve damage (Loprinzi, J Clin Oncol 2020).
Information on this site
is provided for informational purposes only. It is not an endorsement of any
product nor is it meant to substitute for the advice provided by physicians or
other healthcare professionals. The information contained herein should not be
used for diagnosing or treating a health problem or disease. Consumers should
inform their healthcare providers of the dietary supplements they take.
Latest Clinical Research Updates for Acetyl-L-Carnitine
Supplements During Chemotherapy?
9/28/2021
If you are getting
chemotherapy, experts now recommend avoiding acetyl-L-carnitine. Also, see what
they have to say about using alpha-lipoic acid, vitamin B-12 and vitamin E.
Acetyl-L-carnitine + Alpha-Lipoic Acid for Lowering Blood
Pressure?
8/28/2020
We were recently asked if
taking a combination of acetyl-L-carnitine and alpha-lipoic acid can help lower
blood pressure. Find out what research shows in the What It Does section
of the Acetyl-L-Carnitine Supplements Review. Also see our answer to the
question: Which supplements can help to lower blood pressure?
12/02/2018
Supplementing with
L-carnitine can raise blood levels of TMAO which can potentially advance
atherosclerosis. However, the science is not clear, as suggested by a recent
study. Get the details in the L-Carnitine section
of the Acetyl-L-Carnitine Supplements Review.
1/28/2018
A study in which
L-carnitine was given to women during chemotherapy had a surprising result: It
worsened side effects. Get the details in the Concerns and Cautions section
of the Acetyl-L-Carnitine Supplements Review.
Concern Over Carnitine Causing Cardiovascular Disease
4/14/2013
Intake of L-carnitine
from supplements (and from red meat) may foster atherosclerosis (hardening of
the arteries), according to new research. Once ingested, L-carnitine is
converted in some people to a compound which reduces the normal clearing of
cholesterol from arteries.
For more details, see the updated reviews of B Vitamin Supplements & Energy
Drinks and Protein Powders, as some
of these products contain L-carnitine. The Acetyl-L-Carnitine Supplements review
has also been updated because acetyl-L-carnitine is chemically similar to
L-carnitine, suggesting a potential concern.