If you're looking to put a little extra pep in your step, carnitine may be something to consider. Carnitine is a naturally occurring amino acid derivative that plays a role in energy production. Some studies suggest potential benefits of carnitine supplementation, such as supporting metabolism and mitochondrial function, helping with nerve comfort, providing antioxidation, and supporting cardiovascular and neurodegenerative health (16).
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What is Carnitine?
Carnitine is an amino acid derivative responsible for transporting long-chain fatty acids into the energy-producing cell units (the mitochondria). Carnitine is a conditionally essential nutrient, meaning it can be made by the body and obtained through food or dietary supplements. In certain scenarios, the body's requirements may exceed an individual's capacity to synthesize it. Endogenous carnitine is synthesized from the amino acids lysine and methionine in the kidneys, liver, and brain. (7, 15)
Carnitine's primary function is to facilitate the conversion of fatty acids into cellular energy through beta-oxidation. Carnitine acts as a transport carrier, shuttling long-chain fatty acids across the mitochondrial membrane, enabling their utilization for energy production. Beta-oxidation is a vital biochemical process, especially in tissues with high energy demands, such as the heart and skeletal muscles. (15)
Supplemental carnitine is available in several different forms. Each form has unique characteristics and potential benefits; determining which form is best will depend on the goal of supplementation. L-carnitine, a derivative of the amino acid lysine, is the most widely available, least expensive, and best-studied form of carnitine. Acetyl-L-carnitine is the acetylated form of L-carnitine. Acetyl-L-carnitine is more easily absorbed in the gut and transported across the blood-brain barrier than L-carnitine. Acetyl-L-carnitine is commonly the preferred form in trials studying brain health. Propionyl-L-carnitine is an ester form of L-carnitine commonly used in studies for heart health. The body can convert carnitine between its various forms and transport it between tissues as needed, depending on the cells' metabolic needs. (1, 5)
The Top 5 Areas of Carnitine Research
Supplemental carnitine has been studied for various potential health benefits. In this section, we will discuss five areas in which the role of carnitine has been extensively researched.
1. Energy Metabolism and Endurance
Mitochondria play a central role in energy metabolism within cells, serving as the powerhouses responsible for generating adenosine triphosphate (ATP), the primary energy currency of cells. ATP is essential for various cellular functions and activities. Mitochondria are surrounded by an outer and inner membrane. The space enclosed by the inner membrane is known as the mitochondrial matrix. The key steps in energy metabolism occur in different parts of the mitochondria. Carnitine plays a pivotal role in energy production by facilitating the transport of fatty acids into the mitochondrial matrix, where they undergo oxidation to produce energy. (17)
Because maximal exercise in trained athletes is associated with a decrease in plasma L-carnitine, restoring levels with supplementation is theorized to benefit athletic performance. Some studies have explored the impact of carnitine supplementation on athletic performance, with some suggesting that taking 2 grams of L-carnitine, either before exercise or daily for up to 24 weeks, may help improve exercise capacity, reduce the perception of effort, delay the onset of fatigue, and reduce post-exercise muscle discomfort. (14, 19, 33)
2. Weight Management
Carnitine has been explored for its potential role in weight management, with some studies providing insights into its effectiveness. L-carnitine's role in fatty acid oxidation may support fat metabolism and, to some degree, affect the burning of carbohydrates, potentially contributing to weight management when combined with a low-calorie diet and exercise. (1)
Meta-analyses show that taking L-carnitine in doses of 250 mg to 4 grams daily may help reduce weight and body mass index by a small amount. Oral L-carnitine in doses of 2 grams daily taken for up to six months appears to offer the most benefit in supporting weight management. Interestingly, follow-up subgroup analyses show that L-carnitine may only support weight and BMI reduction in overweight and obese patients. (2, 27, 32)
The potential of L-carnitine has also been evaluated in combination with pharmaceutical weight-management medications. Research shows that taking 2 grams of L-carnitine daily with 360 mg of orlistat or 10 mg of sibutramine for one year may enhance weight management outcomes compared to drug monotherapy in patients with type 2 diabetes.
3. Cardiovascular Health
The heart requires adequate levels of carnitine to function properly. Carnitine is involved in oxygen utilization and energy metabolism within the heart's muscular tissue and may act as an antioxidant. These antioxidant properties may help manage the production of fatty acid metabolites that can disrupt cellular membranes and cause oxidative stress, which is implicated in cardiovascular health. During ischemic events, carnitine may help manage fatty acid ester accumulation, which can lead to heart arrhythmias. These properties make carnitine potentially beneficial in supporting recovery from heart attack and managing symptoms of angina, arrhythmia, and congestive heart failure. (17, 34)
Additionally, some evidence suggests that carnitine may support cardiovascular risk factors, including cholesterol and insulin sensitivity. Carnitine may help support lipid profiles by managing triglycerides and cholesterol levels. One meta-analysis suggests that taking 200 mg to 3 grams of L-carnitine daily may help manage plasma glucose, insulin, and HbA1c levels.
Peripheral artery disease (PAD) is a condition in which narrowed arteries, caused by atherosclerosis, reduce blood flow to the arms and/or legs. It often presents with intermittent claudication, lower extremity muscle discomfort that occurs during movement and exercise. Some clinical studies have suggested that propionyl-L-carnitine may help improve walking capacity and quality of life in patients with PAD and intermittent claudication.
4. Diabetic Neuropathy
Diabetic patients commonly exhibit diminished serum carnitine levels (15). Diabetes also increases the risk of atherosclerotic cardiovascular disease and compromised kidney and liver function. Carnitine, especially L-propionyl carnitine, may support peripheral vascular and nerve function in diabetic patients. In light of these factors, managing neuropathy with carnitine may be beneficial for individuals with diabetes. (3)
Peripheral nerve dysfunction, called diabetic neuropathy, occurs in about 50% of people with diabetes mellitus and causes chronic nerve discomfort in one-third of this population subset (17). A 2019 Cochrane review concluded that acetyl-L-carnitine may support nerve fiber health and improve vibratory sensations. Studies included in this analysis suggest that taking acetyl-L-carnitine in doses of 2-3 grams daily for up to one year may modestly reduce neuropathy-associated discomfort scores by about 15 points on a 100-point visual analog scale. (29)
5. Cognitive Function
Alzheimer's disease is characterized by the accumulation of plaques and neuronal degeneration, particularly affecting cholinergic neurons involved in memory functions. These neurons use acetylcholine, and Alzheimer's management often involves supporting acetylcholine levels. Carnitine may be conditionally essential for individuals with Alzheimer's, as it supports acetylcholine synthesis and helps manage toxic compounds, potentially supporting mitochondrial function associated with brain health. A 2003 meta-analysis, including 21 clinical trials and over 1,000 adults with mild cognitive impairment or mild Alzheimer's disease, found that those taking acetyl-L-carnitine showed better clinical and psychometric scores compared to the placebo groups, suggesting potential cognitive support from acetyl-L-carnitine. (6)
Some clinical research also suggests that acetyl-L-carnitine may support cognitive function and memory in elderly individuals with age-related cognitive decline. The mechanisms underlying these neuroprotective effects to support brain health are believed to include enhanced mitochondrial function, neuroprotection against oxidative stress, and potential modulation of neurotransmitter systems. (31)
Dietary Sources of Carnitine
Meat and dairy products are the major natural dietary sources of carnitine. Red meat, such as beef and lamb, stands out as a particularly rich source of carnitine, providing substantial amounts per serving. Plant-based foods, such as grains, fruits, and vegetables, contain very little to no carnitine. The table below lists carnitine-rich foods and their approximate carnitine content per serving. Studies indicate that a typical omnivorous diet provides 24-145 mg of carnitine daily, whereas vegan diets only provide about 1.2 mg. (6, 23)
The bioavailability of dietary carnitine ranges from 63-75%. This is much greater than the absorption rates of supplemental L-carnitine, which vary from 14-18%. (6)
Supplementation: Dosage and Safety
Following established guidelines is important to ensure safety and efficacy when considering carnitine supplementation. Recommended dosages may vary based on specific health goals. Because individual requirements can differ, it's advisable to consult with a healthcare professional to determine an appropriate dosage tailored to your specific needs. (23)
Common doses of the various forms of carnitine are as follows:
- L-carnitine: 2 grams daily
- Acetyl-L-carnitine: 1.5-3 grams daily
- Propionyl-L-carnitine: 1.5-2 grams daily
While carnitine supplements are generally well-tolerated, potential side effects can include gastrointestinal discomfort, nausea, diarrhea, and a fishy body odor. To minimize these risks, starting with lower doses and gradually increasing while monitoring your body's response is recommended. (23)
Individuals with certain medical conditions or those taking specific medications should exercise caution. Carnitine supplements might not be suitable for people with seizure or thyroid disorders, and those on anticoagulant medications should consult with a healthcare provider before supplementation. (20)
Choosing reputable sources for carnitine supplements is essential to ensure product quality and purity. Regular health check-ups and open communication with healthcare professionals can help manage potential risks and ensure that carnitine supplementation aligns with overall health objectives. Always prioritize safety and be attentive to unexpected reactions, discontinuing use if adverse effects occur.
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Summary
The potential of carnitine spans various health domains, showcasing its significance in energy metabolism, cardiovascular health, cognitive function, and more. Carnitine, a naturally occurring compound, has been studied for its potential impact on conditions like cardiovascular health, diabetic neuropathy, and age-related cognitive decline. Adopting a balanced approach is crucial to maximize carnitine's potential benefits. This involves incorporating carnitine-rich foods into one's diet, such as meats and dairy, alongside considering responsible supplementation when necessary. Striking a balance between dietary sources and supplements ensures optimal carnitine intake, promoting overall well-being. As with any health strategy, consulting healthcare professionals is recommended to tailor approaches to individual needs and health goals, fostering a comprehensive and personalized approach to maximizing the potential benefits of carnitine.
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