L-carnitine (carnitine) supplements have gained attention for their potential effects on hormones, fertility, and metabolism. L-carnitine is a naturally occurring compound in the body that plays a crucial role in energy metabolism by helping to transport fatty acids into cells' mitochondria, where they are converted into energy.
This article explores the impact of L-carnitine supplementation on hormones, metabolism, and reproductive health.
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What is L-Carnitine?
Carnitine is an essential nutrient for energy production, playing a crucial role in transporting fatty acids into the mitochondria. Approximately 95% of the body’s carnitine is stored in the skeletal muscle and heart.
Carnitine can be obtained through diet, synthesized by the body, or taken as a supplement. Vegetarians and vegans, who may have lower dietary intake of carnitine, often rely more on the carnitine synthesized by their bodies. If carnitine is not provided through diet, the brain, liver, and kidneys can produce it from individual amino acids. While animal products are the richest sources of carnitine, some plant-based foods also contain small amounts.
L-carnitine is the most widely available supplement form of carnitine, but there are other forms, such as acetyl-L-carnitine and propionyl-L-carnitine. Acetyl-L-carnitine is commonly used in neurological studies due to its potential effects on cognitive function, while propionyl-L-carnitine is often studied for its benefits on cardiovascular health.
L-carnitine supplementation may influence hormone levels, particularly testosterone, which is important for both men's and women's reproductive health. Some studies indicate a positive effect on sperm quality and motility in men, as well as potential benefits for female fertility.
Additionally, L-carnitine may aid in metabolism, offering potential benefits for weight management and energy levels. It has also shown positive effects on athletic performance in some studies.
Evidence on Using L-Carnitine for Hormone Support
Various research studies suggest that L-carnitine can support PCOS and hypothyroidism, which are two of the top most common hormonal conditions.
Polycystic Ovary Syndrome (PCOS)
Polycystic ovary syndrome (PCOS) is a disorder characterized by a hormone imbalance that can cause insulin resistance, irregular menstruation, weight gain, infertility, body hair, and acne.
PCOS patients may be lacking in fatty acid utilization and have been found to have decreased L-carnitine levels, which may be associated with their higher risk for hormone imbalance and insulin resistance, even when they were in the normal range for BMI.
Studies showed that women with PCOS who were given L-carnitine supplementation had improved body mass index, low-density lipoprotein (LDL) levels, total cholesterol, and triglyceride levels.
Hypothyroidism
Hypothyroidism is a condition where the thyroid gland does not produce enough hormones to meet the demands of the body, and may cause weight gain, heavy menstrual periods, fatigue, constipation, and weakness.
Fatigue can be present despite taking thyroid medication, and studies have found fatigue improves with L-carnitine supplementation.
Evidence on Boosting Metabolism with L-Carnitine
Research also suggests that L-carnitine can help boost metabolism.
L-Carnitine for Reducing Inflammation
L-carnitine can reduce free radicals after exercise, reducing inflammation. Supplementation has been shown to increase exercise performance and reduce oxidative stress.
In a double-blind, randomized, placebo-controlled trial, subjects were able to increase their bench press and leg press weight.
Additionally, their power during exercise and overall exercise recovery was improved with L-carnitine supplementation.
Supplementation also improved muscle mass, exercise tolerance, and mental sharpness in elderly patients.
L-Carnitine for Maintaining Healthy Body Weight
Carnitine supplementation has been shown to improve energy metabolism and promote a healthy weight.
L-carnitine supplementation in adults improved body weight, fat mass, and body mass index. This is most likely due to an increase in fatty acid metabolism and carbohydrate use for energy. Results were more apparent in study subjects who were overweight or obese.
L-carnitine supplements can be a helpful tool in a weight loss journey and are best combined with a healthy diet and physical activity.
L-carnitine supplementation has been shown to reduce glucose levels in the blood, circulating insulin levels, and HbA1c (a measure of blood sugar over time). Additionally, L-carnitine supplementation may be beneficial in the treatment of diabetic nerve pain.
Evidence on Using L-Carnitine for Fertility Support
L-carnitine has also been shown to be supportive of fertility for both men and women.
L-Carnitine for Male Fertility Support
As many as 20-30% of infertility cases are due to male infertility. Most of the male factor infertility is due to decreased sperm health, concentration, and motility.
Oxidative stress can impact sperm via DNA damage, lipid oxidation, and a decrease in sperm quality. L-carnitine appears to increase antioxidant defense and prevent these free radical attacks on sperm.
Supplementation with 1 to 3 grams of L-carnitine per day for 3 to 6 months improved sperm motility, morphology (size and shape), and sperm count. In some studies, pregnancy rates improved for couples when L-carnitine supplementation was utilized by the male partner.
L-Carnitine for Female Fertility Support
Women with PCOS often struggle with infertility and may need ovulation-stimulant medications Unfortunately, some women with the condition are resistant to these ovulation-inducing medications, making it even more difficult for them to become pregnant.
Studies have found that L-carnitine supplementation with Clomid improved ovulation rate, increased pregnancy rates, and improved body mass index and lipid levels.
When L-carnitine supplementation was administered along with gonadotropin therapy, ovulation was improved, pregnancy rates increased, and the inner lining of the uterus was thickened (endometrium).
Other Known Benefits of L-Carnitine Supplementation
Beyond hormone support, metabolism, and fertility, L-carnitine supplementation can be used to support other conditions as well.
L-Carnitine for Cardiovascular Health
Carnitine has been shown to improve cardiovascular health by acting as an antioxidant and improving lipid profiles. Because carnitine facilitates fatty acid transport into the mitochondria, it can help prevent the build-up of fat metabolites.
These metabolites can promote oxidative stress, part of the physiology behind heart disease. Carnitine also prevents arrhythmias during heart attacks by reducing inflammation.
L-Carnitine for Healthy Lipid Levels and Glucose
Unhealthy lipid levels, specifically high LDL and triglycerides, promote the formation of plaques in the arteries that supply blood to the heart muscle.
This results in a condition called atherosclerosis, which can cause heart attacks. L-carnitine supplementation has been shown to lower triglycerides and LDL while raising HDL (a beneficial form of cholesterol).
The positive effects of L-carnitine supplementation on glucose levels and insulin are also beneficial to the heart and circulatory system.
L-Carnitine for Neurological Health
A form of carnitine called acetyl-L-carnitine has been studied for its neuroprotective effects. Individuals who took acetyl-L-carnitine had improved cognitive function scores compared to those who were not given the supplement.
Other studies showed improved memory and brain function in elderly patients who were experiencing cognitive impairment. These effects may be similar to how carnitine benefits heart health through antioxidant function and improved fatty acid metabolism.
Alzheimer's disease and cognitive decline can be devastating for patients and families. Data on cognitive improvement through carnitine supplementation shows promise for helping prevent and treat this terrible disease.
How to Supplement with L-Carnitine
Understanding dosages and potential side effects is essential before beginning a new supplement regimen.
Recommended Dosages
L-carnitine and acetyl-L-carnitine are the two most common forms of carnitine supplementation. The dosage ranges can vary vastly from about 3 mg to 5,000 mg. Therefore, consulting with a healthcare provider regarding dosage is advised to help individualize recommendations and to ensure safety.
Safety and Side Effects of L-Carnitine Supplementation
Potential side effects of carnitine supplementation include:
- Gastrointestinal distress
- Nausea
- Changes to body odor
L-carnitine supplements may interact with certain medications, so consulting a healthcare provider before starting a new supplement is recommended.
One aspect of L-carnitine supplementation to consider is its potential to increase trimethylamine-N-oxide (TMAO) levels. TMAO is an amine oxide that is correlated with inflammation and damage to the inner lining of the vessels (atherosclerosis). It is formed by the gut bacteria and higher levels may occur after intake of animal products.
In some studies, L-carnitine supplementation was correlated to higher levels of TMAO, but these subjects did not have higher levels of inflammation or stress markers of oxidation. This suggests that the higher levels of TMAO in these subjects were not causing inflammation or damage to the arteries. Further studies are needed to explore the relationship between L-carnitine supplementation and TMAO.
How to Choose an L-Carnitine Supplement
As with all supplements, it is important to consult a healthcare provider before starting L-carnitine. It is important to consider the source and brand of L-carnitine supplementation to ensure purity and dosage accuracy.
Because supplements are not regulated by the Food and Drug Administration, it is important to choose a supplement that is third-party approved. Third-party certification seals are present on packing, indicating that the product meets their standards.
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Key Takeaways
- L-carnitine supplements hold promise for impacting hormone levels, fertility, and metabolism.
- These supplements, derived from a naturally occurring compound in the body, are essential for energy metabolism by aiding in the transport of fatty acids into cells' mitochondria.
- Research suggests potential benefits for hormone balance, particularly in conditions like polycystic ovary syndrome (PCOS), where L-carnitine supplementation has shown improvements in body mass index, cholesterol levels, and ovulation rates.
- L-carnitine supplementation may support weight management efforts and enhance exercise performance, with positive effects observed in reducing oxidative stress and improving muscle mass.
- For male fertility, L-carnitine supplementation has demonstrated improvements in sperm health, including motility and morphology, potentially leading to increased pregnancy rates.
- Consult a healthcare provider for a tailored recommendation about L-carnitine supplements and dosage.
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