L-carnitine is a nonessential amino acid that your body uses to convert fat into energy. Hormones produced by your thyroid gland control the balance of energy in your body, particularly how your body uses fat stored for energy. When your thyroid gland cannot produce adequate levels of thyroid hormones, a medical condition called hypothyroidism develops. Some evidence suggests that taking L-carnitine supplements may worsen symptoms of hypothyroidism. Talk openly with your doctor about any dietary supplements you are taking when diagnosed with hypothyroidism.
L-Carnitine
Your body can produce adequate levels of L-carnitine from other amino acids under most conditions. Your body turns fatty acids into energy within cellular compartments called mitochondria. L-carnitine binds to fatty acids in order to transport them into the mitochondria. Wastes produced during the burning of fat are also removed from the mitochondria by L-carnitine. People with some metabolic or vascular diseases, such as type 2 diabetes or heart disease, may be unable to produce or transport adequate levels of L-carnitine throughout the body. You may benefit from taking L-carnitine supplements under these conditions.
Hypothyroidism
When your body does not produce normal levels of thyroid hormones, you tend to store fat rather than use it. Symptoms of hypothyroidism may include unexplained weight gain, poor immune function, weakness, fatigue, mood disturbances, sensitivity to cold, brittle hair or nails, thickened skin and poor wound healing. Your doctor will perform tests to measure the levels of hormone stimulating your thyroid gland, as well as levels of thyroid hormones in your blood in order to determine whether you have hypothyroidism. Iodine deficiency and damage to the thyroid gland can be possible causes of hypothyroidism.
Possible Interactions
Elevation of levels of L-carnitine in your body may favor use of fatty acids rather than sugar for energy. With hypothyroidism, your body has difficulty using stored body fat. However, research has not proven that L-carnitine has a significant effect on people with hypothyroidism. If you have hypothyroidism and you are interested in taking L-carnitine, discuss the options with your doctor.
Safety
No significant health effects have been demonstrated for L-carnitine supplements. According to the Linus Pauling Institute, people taking more than 3,000 mg of L-carnitine per day have reported a fishy body odor. Some have also reported diarrhea, nausea and other gastrointestinal issues common when taking large amounts of dietary supplements. Only the L-form of carnitine is active in your body; Supplements containing D-carnitine can interfere with your body's use of L-carnitine.
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