Tired? You Could Be Deficient in This Important Nutrient. An Expert’s Take

When you switch to a vegan or plant-based diet you probably get asked, or worry about, getting enough vitamin B12 since that is known to come from meat and fish. Or you may be concerned with protein, though you quickly learn that legumes, vegetables, whole grains and nuts and seeds offer plenty of protein to be healthy without meat and dairy. But there may be one nutrient you have not heard of that could leave you feeling fatigues or experiencing muscle weakness, which is carnitine.

Carnitine is a compound that plays a critical role in energy production in the body, especially in how your cells burn fat for fuel. And while most people produce enough carnitine on their own, without the help of animal products in their diet, carnitine can become depleted in some people following a vegan or plant-based diet.

Carnitine is found in animal foods, so many people think that a vegan diet leaves you lacking in this important nutrient. Read on to learn carnitine's vital role in the body, how you can get enough carnitine on a plant-based diet, and whether you need to consider carnitine supplementation.

Carnitine is a compound derived from amino acids and found throughout all tissues of your body, according to the National Institutes of Health (NIH). It plays an essential role in energy metabolism and removing waste products and cellular toxins. Carnitine has two forms — D and L. L-carnitine is the active form produced by the body and found in food. “The human body usually produces all the carnitine it requires,” explains Lon Ben-Asher, MS, RD, a registered dietitian with Pritkin. “Only in specific situations, such as genetic and medical reasons, does it become a conditionally essential nutrient where it's required through food or supplement intake.”

Even if your diet is low in carnitine, your kidneys generally produce sufficient amounts of the compound from the amino acids lysine and methionine (precursors to carnitine) to meet daily requirements. Also, your body is efficient at maintaining carnitine homeostasis (balance in the body) with the kidneys' excretion and reuptake of amino acids.

Symptoms that may show up if you are deficient in carnitine include, according to Cedars Sinai Medical Library:

There are two types of carnitine deficiency — primary and secondary. Primary carnitine deficiency is caused by a genetic disorder that usually occurs by age 5. Symptoms include heart disease, skeletal-muscle weakness, and hypoglycemia (low blood sugar). Secondary carnitine deficiency occurs from specific health issues or under certain conditions (e.g., kidney failure or antibiotic use) that lower carnitine absorption or increase its excretion. There are several signs of secondary carnitine deficiency, including muscle weakness, fatigue, irritability, and delayed motor development in kids.

Most healthy adults and kids don’t need to worry about carnitine deficiency or taking supplements for the reasons noted above. However, if you have inadequate levels due to a health condition or from medications, you can supplement with a standard dose of 0.5 to 2 grams per day. Be careful not to exceed 3 grams as this can reach toxic levels, with adverse effects such as nausea, vomiting, diarrhea, abdominal pain, and a “fishy” body odor.

“If [someone] has chronic [kidney] disease, a secondary carnitine deficiency may result due to the kidney's increased excretion of amino acids (e.g., lysine and methionine) therefore consumption of foods rich in carnitine and/or supplementation may be appropriate,” advises Ben-Asher.

A small study published in the European Journal of Nutrition compared the carnitine concentrations in the blood and muscle tissue between sixteen vegetarians and eight omnivores. All participants were male and given oral supplementation of 2 grams of L-carnitine for 12 weeks. The researchers found that the vegetarians had lower blood carnitine concentrations, but equivalent muscle carnitine levels compared to the omnivores. Oral supplementation of L-carnitine showed a normalization of the blood carnitine and a slight increase in muscle carnitine amongst the vegetarians. The biggest takeaway was that vegetarians don’t experience impaired muscle function or energy metabolism as a result of carnitine deficiency.

The foods with the highest amounts of carnitine are red meat, chicken, fish, eggs, and dairy. This makes sense, considering carnitine’s name is derived from the Latin carnus (or flesh) as the compound was first isolated from meat. Fortunately, eating plant-based foods high in the amino acids lysine and methionine helps ensure your body produces adequate amounts of carnitine.

Plant-based foods high in lysine include:

Methionine-rich plant foods include:

“Because carnitine is produced naturally by the human body, there is no established RDA or DRIs,” states Ben-Asher. "A healthy individual will usually produce all the carnitine they need by the cells to convert fat into energy production, therefore there is no need to obtain from other sources.” So unless you have an underlying medical condition or genetic disorder, there’s no need for vegans to supplement carnitine.

Eating plant-based foods high in carnitine precursors will prevent deficiency. Combining plant-based sources of lysine and methionine with plant foods rich in vitamin C, vitamin B6, iron, magnesium, and niacin can also enhance carnitine production.

If you’d still prefer to supplement for insurance, there are two types of carnitine supplements: L-carnitine and acetyl-L-carnitine. The NIH states that acetyl-L-carnitine is more readily absorbed by the small intestine and is more effective at crossing the blood-brain barrier, meaning it’s more easily absorbed by the brain. In addition, acetyl-L-carnitine can improve brain function and reduce deterioration in older adults with mild cognitive impairment and Alzheimer’s disease, says the NIH. However, L-carnitine is more affordable and is still effective at increasing carnitine production.

Vegans with chronic kidney disease can benefit from carnitine supplementation, according to the NIH. Kidney disease causes the kidneys to produce less and eliminate more carnitine than normal which significantly increases a person’s risk of carnitine deficiency. Remember to not exceed 3 grams per day and check with your doctor before taking a carnitine supplement.

Carnitine is a critical nutrient used for energy metabolism and the removal of toxic waste products. Healthy vegans free from kidney disease and medication use don’t need to supplement carnitine. Eating plant-based foods high in the amino acids lysine and methionine help the kidneys produce enough carnitine for good health and to help you thrive.

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