L-carnitine
L-Carnitine in Synaptril: Plain Carnitine, Not the Acetyl Form
L-carnitine and the brain is a thin research topic: memory trials used another form, acetyl-L-carnitine, at 1.5 to 3 grams a day. Synaptril lists plain L-carnitine as line 4 of its 575 mg blend. Blend math caps it at about 58 mg a capsule, a few percent of any studied dose.
Written by the Synaptril label deskUpdated
The basics01
What is L-carnitine, and what does it do for the brain?
L-carnitine is a compound the body uses to carry fatty acids into mitochondria, the parts of a cell that burn fuel for energy. Its link to the brain is mostly indirect, and the brain research centers on a related form.
Synaptril lists "L-Carnitine" fourth of six in its 575 mg blend, with no amount and no salt form.
L-carnitine trials usually used 1 to 4 grams a day, and the evidence on memory is called unclear (NIH ODS, Carnitine).
| Name on the label | L-Carnitine |
|---|---|
| What it is | Amino acid derivative that carries fats into mitochondria |
| Place on the label | Line 4 of 6 in the 575 mg proprietary blend |
| Amount per capsule | At most 58 mg (label order and magnesium math); 144 mg by label order alone |
| Amount used in research | Memory trials used acetyl-L-carnitine at about 1.5-3 g a day |
| Strength of evidence | Not shown for memory as plain L-carnitine |
| Marketed or traditional use | Fat transport for energy production |
| Main caution | Fishy body odor and stomach upset at about 3 g a day; some seizure medicines lower carnitine levels. |
Two forms02
Is L-carnitine the same as acetyl-L-carnitine?
No, L-carnitine and acetyl-L-carnitine are different forms, and the memory studies used the acetyl form. Synaptril's label names only plain L-carnitine.
Acetyl-L-carnitine carries an extra acetyl group. Memory studies gave it at about 1.5 to 3 grams a day (NIH ODS, Carnitine), and a Cochrane review covered that form only (Cochrane, Acetyl-L-carnitine for dementia). Its findings do not carry over to plain L-carnitine, or to a far smaller dose.
| Point | L-carnitine in Synaptril | Acetyl-L-carnitine in memory trials |
|---|---|---|
| Form on the label | "L-Carnitine", no salt named | Acetyl-L-carnitine |
| Amount | Not printed; at most about 58 mg | About 1,500-3,000 mg a day |
| Main finding | Not tested | Small, short-lived gains; not recommended for routine use |
The evidence03
Does L-carnitine improve memory?
L-carnitine has not been shown to improve memory. The closest evidence is acetyl-L-carnitine in people with cognitive decline, and those gains faded.
The Cochrane team pooled 16 double-blind trials (Cochrane, Acetyl-L-carnitine for dementia). There was no gain in dementia severity or daily function. The authors found "no evidence to recommend its routine use in clinical practice."
- 12 weeks
Clinicians' global impressions leaned toward acetyl-L-carnitine.
- 24 weeks
Global impressions still favored it, and the memory test score rose by 0.69 points.
- 52 weeks
The advantage on global impressions was gone.
None of it tested plain L-carnitine. If your memory has changed, see a doctor first, since low B12, thyroid problems and medicine side effects are treatable causes (NIA, Memory Problems and Aging).
Blend math04
How much L-carnitine is in a Synaptril capsule?
A Synaptril capsule holds at most about 58 mg of L-carnitine, and probably less. That ceiling comes from the label's own numbers.
The label prints 80 mg of magnesium from magnesium glycinate. Magnesium glycinate is about 14% magnesium by weight (GlobalRPH, Magnesium Glycinate), so it takes about 567 mg to supply 80 mg. That leaves roughly 8 mg of the 575 mg blend for the other five.
In the generous case, a 20% grade, magnesium glycinate fills 400 mg and leaves 175 mg for five ingredients. L-carnitine is fourth, so it cannot outweigh the three lines above it: 175 divided by 3 is about 58 mg.
That is under 4% of 1,500 mg, the low end of the acetyl-L-carnitine memory dose. Reaching it would take about 26 capsules, and the label says one a day.
The full arithmetic for all six lines is in how Synaptril works.
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See packsSafety05
What are the side effects of L-carnitine?
L-carnitine side effects show up mostly at about 3 grams a day: nausea, vomiting, stomach cramps, diarrhea and a fishy body odor (NIH ODS, Carnitine). A Synaptril capsule holds a small fraction of that.
Gut bacteria turn unabsorbed carnitine into TMAO, linked to heart disease risk; what that means is not well understood (NIH ODS, Carnitine).
Seizure medicines
Valproic acid, phenobarbital, phenytoin and carbamazepine lower blood carnitine levels (NIH ODS, Carnitine). Ask the prescriber first.
Pivalate antibiotics
Antibiotics bound to pivalate also lower carnitine levels (NIH ODS, Carnitine). Your pharmacist can check yours.
A supplement never replaces a seizure drug or any prescription. More on Synaptril side effects and in L-carnitine side effects.
Mental energy06
Does L-carnitine give you mental energy?
L-carnitine has not been shown to give mental energy at Synaptril's amount. Its energy role is about fat transport in cells, which is not the same as feeling alert.
The bottle says "Boosts Mental Energy*". Tufts researchers define mental energy as mood, motivation and attention, and found supplement evidence inconsistent (Tufts, Mental Energy Claims).
L-carnitine is not a stimulant, and the label lists no caffeine, so do not expect a coffee-like lift. See does L-carnitine give you energy for the longer answer.
Verdict07
Is the L-carnitine in Synaptril worth it?
The L-carnitine in Synaptril is a minor extra: the wrong form for the memory research, and far below the studied dose.
Pros
- Named plainly on the label
- Far below the 3 g level tied to stomach upset and odor
- No stimulant effect
Cons
- Plain form, not the acetyl form used in memory trials
- At most about 58 mg, under 4% of the studied low end
- No trial at any small dose
If carnitine is the reason you are looking at Synaptril, compare the amounts first on the Synaptril ingredients page.
FAQ08
L-carnitine questions, answered
Does Synaptril use acetyl-L-carnitine?
No. The Synaptril label lists "L-Carnitine", the plain form, with no acetyl group named. The memory research used acetyl-L-carnitine at about 1.5 to 3 grams a day, so those results do not describe the ingredient in this capsule.
How many Synaptril capsules equal one studied L-carnitine dose?
About 26 capsules, even at the generous ceiling of 58 mg each, to reach 1,500 mg, the low end of the acetyl-L-carnitine memory dose. The label allows one capsule a day, so never take more.
Will the L-carnitine in Synaptril cause fishy body odor?
It is unlikely. Fishy body odor and stomach upset are reported at about 3 grams of L-carnitine a day. A Synaptril capsule holds at most about 58 mg, which is less than 2% of that amount.
Can I take Synaptril with valproic acid?
Ask your prescriber first. Valproic acid and some other seizure medicines lower blood carnitine levels, and the Synaptril label asks anyone on a medication to consult a physician. Do not change your seizure medicine on your own.
Why is L-carnitine fourth on the Synaptril label?
Proprietary blends list ingredients from most to least by weight. Fourth place means L-carnitine weighs less than magnesium glycinate, alpha lipoic acid and butcher's broom, but more than turmeric extract and CoQ10. Its exact amount is not printed.
Who wrote this09
Written and reviewed by
Pages built from the label, the sales page and linked NIH, FDA, CDC, FTC and peer-reviewed sources.
Last updated . Learn about our editorial standards and how we check reviews. This website is run by a U.S. retail partner of Synaptril, not by the manufacturer or the distributor. We make money when you buy through our order links.
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