Carnitine is found in the bodies of all mammals and many other living organisms. Carnitine’s most well-known function is transporting fatty acids into each cell’s mitochondria (the energy center of the cell) for breakdown into energy.
The word carnitine is composed of the root word carne, meaning flesh. Red meat is a good source of carnitine but according to the National Institutes of Health (NIH), eating red meat can shorten your life span.
Fortunately carnitine can be found in commonly consumed plants. There are a variety of sources including nuts and seeds. The following list has been compiled using radioisotopic technology to determine the carnitine content in common foods. This list is by no means complete.
Listing higher sources first:
- Tempeh 100 g contain 19.5 mg
- Cod fish 100 g contain 5.6 mg
- Chicken breast 100 g contain 3.9 mg
- Whole milk 100 ml contain 3.3 mg
- Potatoes 100 g contain 2.4 mg
- Lentils 100 g contain 2.1 mg
- Avocado one medium sized contains 2 mg
- Sweet Potatoes 100 g contain 1.1 mg
- Cottage cheese 100 g contain 1.1 mg
- Raisins 100 g contain 0.8 mg
- Whole wheat bread 100 g contain 0.36 mg
- Carrots 100 g contain 0.3 mg
- Bananas 100 g contain 0.2 mg
- Apples (without skin) 100 g contain 0.2 mg
- Asparagus 100 g contain 0.195 mg
- White bread 100 g contain 0.147 mg
- Peanut butter 100 g contain 0.083 mg
- Rice 100 g contain 0.0449 mg
- Egg 100 g contain 0.0121 mg
- Orange juice 100 ml contain 0.0019 mg
When carnitine occurs in animal tissue, it is synthesized from the amino acids lysine and methionine. Humans synthesize carnitine in their bodies from these amino acids in the same manner that animals do.
According to the National Institutes of Health, healthy children and adults do not need to consume carnitine from food or supplements because the liver and the kidneys produce sufficient amounts to meet daily needs.[4,5,6]
In 1989 The Food and Nutrition Board of the National Academies (formerly National Academy of Sciences) declared that carnitine was not an essential nutrient.
Carnitine deficiencies are rare. Even strict vegetarians and vegans show no signs of carnitine deficiency. The only time I have personally encountered a person deficient in carnitine was when they had been taking CoQ10 in doses of 200 mg a day for extended periods of time. This condition was easily corrected by taking a carnitine supplement and cutting back on CoQ10.
Studies that have been done using carnitine supplements to improve exercise performance show conflicting results. Some studies conclude no significant effect on exercise performance. Other studies conclude a beneficial effect on training, competition and recovery from strenuous exercise.
There are two main forms of carnitine supplements, L-carnitine and acetyl L-carnitine (also sometimes spelled acetylcarnitine or ALCAR).
The supplemental form called L-carnitine is usually taken by people trying to lose weight by converting their fat into energy. However, published studies showing the efficacy of using L-carnitine for weight loss are limited.
The form called acetyl L-carnitine is known to be more easily absorbed by the small intestine and is also known for its ability to pass through the blood brain barrier. Studies conclude that senior citizens with age related mental decline taking acetyl L-carnitine improved their mental functioning, especially in those with Alzheimer’s disease.
In January of 2016 a meta-analysis of randomized controlled trials was published that showed a significant reduction of lipoprotein(a) levels following carnitine supplementation. This is great news for those with genetically high Lp(a) levels because an elevated level of Lp(a) is a risk factor for heart disease and stroke.
One study found benefit for people with pancreatic cancer. Another study found benefit for people with diabetic peripheral neuropathy. Studies are ongoing about the use of carnitine supplements to treat various disease conditions.
Rare side effects of supplementing with carnitine include fishy body odor and rash. Taking large doses could result in nausea, diarrhea and cramps. People on prescription medication or those with heart disease, excessive, fatigue or a thyroid condition should talk to a doctor before taking carnitine.
For people who choose to supplement with carnitine I suggest using the product as directed on the label. No advantage appears to exist in taking an oral dose of carnitine greater than two grams at a time because absorption studies indicate saturation at this dose.
By Craig B Sommers ND, CN
 http://www.nih.gov/news-events/nih-research-matters/risk-red-meat  Demarquoy, Jean; Georges, Béatrice; Rigault, Caroline; Royer, Marie-Charlotte; Clairet, Amélie; Soty, Maud; Lekounoungou, Serge; Le Borgne, Françoise (2004-06-01)."Radioisotopic determination of l-carnitine content in foods commonly eaten in Western countries". Food Chemistry 86 (1): 137–142. doi:10.1016/j.foodchem.2003.09.023  http://www.ncbi.nlm.nih.gov/pubmed/21561431  Rebouche CJ. Carnitine. In: Modern Nutrition in Health and Disease, 9th Edition (edited by Shils ME, Olson JA, Shike M, Ross, AC). Lippincott Williams and Wilkins, New York, 1999, pp. 505-12.  The editors. Carnitine: lessons from one hundred years of research. Ann NY Acad Sci 2004;1033:ix-xi.  National Research Council. Food and Nutrition Board. Recommended Dietary Allowances, 10th Edition. National Academy Press, Washington, DC, 1989.  http://lpi.oregonstate.edu/infocenter/othernuts/carnitine/  Brass EP. Supplemental carnitine and exercise. Am J Clin Nutr 2000;72:618S-23S.  http://www.ncbi.nlm.nih.gov/pubmed/21561431  http://www.ncbi.nlm.nih.gov/pubmed/15212755  http://www.ncbi.nlm.nih.gov/pubmed/1944900  http://www.ncbi.nlm.nih.gov/pubmed/18801359  http://www.ncbi.nlm.nih.gov/pubmed/26754058  http://www.ncbi.nlm.nih.gov/pubmed/22824168  http://www.ncbi.nlm.nih.gov/pubmed/18940920  Bain, Marcus A.; Milne, Robert W.; Evans, Allan M. (2006-10-01). "Disposition and metabolite kinetics of oral L-carnitine in humans". Journal of Clinical Pharmacology 46 (10): 1163–1170.doi:10.1177/0091270006292851. ISSN 0091-2700. PMID 16988205