L-Carnitine - L-Carnitine PDF

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L-Carnitine...

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L-Carnitine: Benefits, Side Effects, Sources and Dosage L-carnitine is a naturally occurring amino acid derivative that’s often taken as a supplement. It is used for weight loss and may have an impact on brain function. However, popular claims about supplements don’t always match up with the science. This article examines the potential risks and benefits of L-carnitine supplements and explains how this nutrient functions in your body.

What Is L-Carnitine? L-carnitine is a nutrient and dietary supplement. It plays a crucial role in the production of energy by transporting fatty acids into your cells’ mitochondria (1Trusted Source, 2Trusted Source, 3Trusted Source). The mitochondria act as engines within your cells, burning these fats to create usable energy. Your body can produce L-carnitine out of the amino acids lysine and methionine.

For your body to produce it in sufficient amounts, you also need plenty of vitamin C (4Trusted Source). In addition to the L-carnitine produced in your body, you can also obtain small amounts by eating animal products like meat or fish (5Trusted Source). Vegans or people with certain genetic issues may be unable to produce or obtain enough. This makes L-carnitine a conditionally essential nutrient (6Trusted Source).

Different Types L-carnitine is the standard biologically active form of carnitine, which is found in your body, foods and most supplements. Here are several other types of carnitine:  D-carnitine: This inactive form may cause a carnitine deficiency in your body by inhibiting the absorption of other, more useful forms (7Trusted Source, 8Trusted Source).  Acetyl-L-carnitine: Often called ALCAR, this is possibly the most effective form for your brain. Studies suggest that it may benefit people with neurodegenerative diseases (9Trusted Source).  Propionyl-L-carnitine: This form is well-suited for circulatory issues, such as peripheral vascular disease and high blood pressure. It may boost production of nitric oxide, which improves blood flow (10Trusted Source, 11Trusted Source).  L-carnitine L-tartrate: This is commonly added to sports supplements due to its rapid absorption rate. It may aid muscle soreness and recovery in exercise (12Trusted Source, 13Trusted Source, 14Trusted Source).

For most people, acetyl-L-carnitine and L-carnitine seem to be the most effective for general use. However, you should always pick the form that’s best for your personal needs and goals.

Role in Your Body L-carnitine’s main role in your body involves mitochondrial function and energy production (3Trusted Source, 15Trusted Source, 16Trusted Source). In cells, it helps transport fatty acids into the mitochondria, where they can be burned for energy. About 98% of your L-carnitine stores are contained in your muscles, along with trace amounts in your liver and blood (17Trusted Source, 18Trusted Source). L-carnitine may help increase mitochondrial function, which plays a key role in disease and healthy aging (19Trusted Source, 20Trusted Source, 21Trusted Source). Newer research illustrates the potential benefits of carnitine’s different forms, which may be used for various conditions, including heart and brain diseases (22Trusted Source, 23Trusted Source). SUMMARY L-carnitine is an amino acid derivative that transports fatty acids into your cells to be processed for energy. It is made by your body and also available as a supplement.

Does It Aid Weight Loss? In theory, using L-carnitine as a weight loss supplement makes sense. Since L-carnitine helps move more fatty acids into your cells to be burned for energy, you might think this would increase your ability to burn fat and lose weight. However, the human body is extremely complex, and the results of both human and animal studies are mixed (24Trusted Source, 25Trusted Source, 26Trusted Source, 27Trusted Source). In an eight-week study in 38 women who exercised four times per week, there was no difference in weight loss between those who took L-carnitine and those who didn’t (24Trusted Source). What’s more, five of the participants taking L-carnitine experienced nausea or diarrhea (24Trusted Source). Another human study monitored L-carnitine’s effect on fat burning during a 90minute stationary bicycle workout. Four weeks of taking supplements did not increase fat burning (28Trusted Source). However, one analysis of nine studies — mostly in obese individuals or older adults — found that people lost an average of 2.9 pounds (1.3 kg) more weight while taking L-carnitine (29Trusted Source). More research is needed to confirm the benefits of L-carnitine in a younger, more active population. While it may aid in weight loss for obese individuals or older adults, a thorough diet and exercise regimen must be in place first.

SUMMARY Although the cellular mechanism of L-carnitine suggests it could benefit weight loss, its effects — if present at all — are small.

Effects on Brain Function L-carnitine may benefit brain function. Some animal studies suggest that the acetyl form, acetyl-L-carnitine (ALCAR), may help prevent age-related mental decline and improve markers of learning (30Trusted Source, 31). Human studies indicate that taking acetyl-L-carnitine daily helps reverse the decline in brain function associated with Alzheimer’s and other brain diseases (32Trusted Source, 33Trusted Source, 34Trusted Source). This form exhibited similar benefits for general brain function in older adults who did not have Alzheimer’s or other brain conditions (35Trusted Source, 36Trusted Source, 37Trusted Source). In specific cases, this form may even protect your brain from cell damage. In a 90-day study, people with alcohol addictions who took 2 grams of acetylL-carnitine per day experienced significant improvements in all measures of brain function (38Trusted Source). More research is needed on long-term benefits for healthy individuals. SUMMARY

L-carnitine — specifically acetyl-L-carnitine — can have beneficial effects on brain function in various diseases.

Other Health Benefits A few more health benefits have been linked to L-carnitine supplements.

Heart Health Some studies demonstrate a potential for reducing blood pressure and the inflammatory process associated with heart disease (23Trusted Source, 39Trusted Source). In one study, 2 grams of acetyl-L-carnitine per day resulted in an almost 10point drop in systolic blood pressure — the top number of a blood pressure reading and an important indicator of heart health and disease risk (23Trusted Source). L-carnitine is also linked to improvements in patients with severe heart disorders, such as coronary heart disease and chronic heart failure (40Trusted Source, 41Trusted Source). One 12-month study observed a reduction in heart failure and deaths among participants who took L-carnitine supplements (42Trusted Source).

Exercise Performance The evidence is mixed when it comes to L-carnitine’s effects on sports performance.

However, several studies note mild benefits associated with larger or more long-term doses (43Trusted Source, 44Trusted Source, 45Trusted Source). L-carnitine’s benefits may be indirect and take weeks or months to appear. This differs from supplements like caffeine or creatine, which can directly enhance sports performance. L-carnitine may benefit:  Recovery: May improve exercise recovery (46Trusted Source, 47Trusted Source).  Muscle oxygen supply: May increase oxygen supply to your muscles (48Trusted Source).  Stamina: May increase blood flow and nitric oxide production, helping delay discomfort and reduce fatigue (48Trusted Source).  Muscle soreness: May reduce muscle soreness after exercise (49Trusted Source).  Red blood cell production: May increase the production of red blood cells, which transport oxygen throughout your body and muscles (50Trusted Source, 51Trusted Source).

Type 2 Diabetes L-carnitine may also reduce symptoms of type 2 diabetes and its associated risk factors (52Trusted Source, 53Trusted Source, 54Trusted Source). One study of people with type 2 diabetes taking anti-diabetic medication indicated that carnitine supplements significantly reduced blood sugar levels, compared to a placebo (55Trusted Source).

It may also combat diabetes by increasing a key enzyme called AMPK, which improves your body’s ability to use carbs (56Trusted Source). SUMMARY Research suggests that L-carnitine may aid exercise performance and treat health conditions like heart disease and type 2 diabetes.

Safety and Side Effects For most people, 2 grams or less per day is relatively safe and free from any serious side effects. In one study, people who took 3 grams every day for 21 days experienced no negative effects (57Trusted Source). In one review of L-carnitine’s safety, doses of approximately 2 grams per day appeared to be safe for long-term use. However, there were some mild side effects, including nausea and stomach discomfort (24Trusted Source, 58Trusted Source). However, L-carnitine supplements may raise your blood levels of trimethylamine-N-oxide (TMAO) over time. High levels of TMAO are linked to an increased risk of atherosclerosis — a disease which clogs your arteries (59Trusted Source, 60Trusted Source). More studies on the safety of L-carnitine supplements are needed. SUMMARY

Doses of 2 grams or less per day seem to be well tolerated and safe for most people. Tentative evidence suggests L-carnitine supplements might increase your risk of atherosclerosis.

Food Sources You can get small amounts of L-carnitine from your diet by eating meat and fish (4Trusted Source, 5Trusted Source). The best sources of L-carnitine are (4Trusted Source):  Beef: 81 mg per 3 ounces (85 grams)  Pork: 24 mg per 3 ounces (85 grams)  Fish: 5 mg per 3 ounces (85 grams)  Chicken: 3 mg per 3 ounces (85 grams)  Milk: 8 mg per 8 ounces (227 ml) Interestingly, food sources of L-carnitine have a greater absorption rate than supplements. According to one study, 57–84% of L-carnitine is absorbed when it’s consumed from food, compared to only 14–18% when taken as a supplement (61Trusted Source). As noted before, your body can also produce this substance naturally from the amino acids methionine and lysine if your stores are low. For these reasons, L-carnitine supplements are only necessary in special cases, such as disease treatment.

SUMMARY The main dietary sources of L-carnitine are meat, fish and some other animal products, such as milk. A healthy individual can also produce sufficient amounts within the body.

Should You Take It? Your L-carnitine levels are influenced by how much you’re eating and how much your body is producing. For this reason, L-carnitine levels are often lower in vegetarians and vegans, since they restrict or avoid animal products (6Trusted Source, 62Trusted Source). Therefore, vegetarians and vegans may want to consider L-carnitine supplements. However, no studies have confirmed the benefits of carnitine supplements in these specific populations. Older adults may also benefit from L-carnitine supplements. Research shows that your levels tend to decline as you age (63, 64Trusted Source). In one study, 2 grams of L-carnitine reduced fatigue and increased muscle function in older adults. Other research reveals that acetyl-L-carnitine may also help boost brain health and function as you age (64Trusted Source, 65Trusted Source). Additionally, the risk of deficiency is higher for those with diseases like cirrhosis and kidney disease. If you have one of these conditions, a supplement may be beneficial (1Trusted Source, 66Trusted Source, 67Trusted Source).

As with any supplement, you should speak with your doctor before taking Lcarnitine. SUMMARY Specific populations may benefit from L-carnitine supplements. This includes older adults and people who rarely or never eat meat and fish.

Dosage Recommendations The standard dose of L-carnitine is 500–2,000 mg per day. Although dosage varies from study to study, here is an overview of the use and dose for each form:  Acetyl-L-carnitine: This form is best for brain health and function. Doses vary from 600–2,500 mg per day.  L-carnitine L-tartrate: This form is most effective for exercise performance. Doses vary from 1,000–4,000 mg per day.  Propionyl-L-carnitine: This form is best for improving blood flow in those with high blood pressure or related health conditions. Doses vary from 400–1,000 mg per day. Up to 2,000 mg (2 grams) per day seems safe and effective in the long term. SUMMARY Although the recommended dose varies, around 500–2,000 mg (0.5–2 grams) seems to be both safe and effective.

The Bottom Line L-carnitine is best known as a fat burner — but the overall research is mixed. It is unlikely to cause significant weight loss. However, studies support its use for health, brain function and disease prevention. Supplements may also benefit those with lower levels, such as older adults, vegans and vegetarians. Of the different forms, acetyl-L-carnitine and L-carnitine are the most popular and seem to be most effective. Reference: https://www.healthline.com/nutrition/5-natural-fat-burners#TOC_TITLE_HDR_6...