ARI Publication 40 – 2013 Version
Carnitine is a substance in the body that carries fuel (long-chain fatty acids) into the mitochondria
(energy-producing organelles inside every cell in the body). It also carries potentially toxic organic
acids out of the mitochondria and cell so they can be eliminated from the body. Mitochondria
produce ATP, a major fuel for the body and the brain. So, carnitine is important for energy
production to fuel the body and the brain.
Carnitine can be made by the body to a limited extent, but much of it comes from our diet,
especially beef and pork. People who eat limited amounts of beef and pork are at higher risk of
carnitine deficiency. Carnitine is widely used as an over-the-counter nutritional supplement, and it
is also available by prescription (it is approved by the FDA for treating carnitine deficiency caused
by certain genetic diseases).
Carnitine levels can be measured in the blood, but for children it is important to have a pediatric
reference range. (Many labs do not.)
If a person is not eating beef or pork, then they are at higher risk of carnitine deficiency (other
protein sources, such as chicken, have only 5% or less of the amount of carnitine present in beef).
Vegetarians are especially at risk of carnitine deficiency.
Carnitine is available as both 1-carnitine and acetyl-1-carnitine. Both forms are useful sources of
carnitine, and the body can convert them to one another. However, several double-blind, placebocontrolled studies have found that acetyl-1-carnitine is helpful for improving cognitive functioning
and memory in adults with Alzheimer’s, so it is possible that the acetyl-1-carnitine form is more
beneficial due to the acetyl group, which can help make acetylcholine, an important
neurotransmitter. Acetyl-1-carnitine has also been found to be neuroprotective.
The amount used in the autism treatment study by Geier et al 2010 (see below) was 50 mg Lcarnitine/kg bodyweight/day up to 1 g/day, and dosages of 0.5 to 2 g/day are common. We suggest starting at a lower dosage, and gradually increasing over several weeks.
About 60% of carnitine in food is absorbed, vs. only about 15% from supplements. So, consuming
9 oz of beef or 1 g of carnitine supplement results in about the same absorption of carnitine.
Physicians Desk Reference (PDRJ for NutritionalSupplements, 2001, P. 255.
A study by Geier et al (2011) found that carnitine supplementation was generally very welltolerated, with rare side effects of irritability and stomach discomfort, and only 1 of 19 children
withdrew due to side-effects. The risk of adverse effects may be reduced by gradually phasing in
the dosage over several weeks. A 1-g dose of carnitine is about equivalent to eating a half-pound