Imagine yourself an older adult at an awesome retirement community, still active with a healthy heart and a healthy mind. Wouldn’t it be great to enjoy the fun retirement you always dreamed of? Although retirement might be a long way away, you probably know that the dietary choices you make today impact your health in the future.
Many variables contribute to staying healthy, but a substance called carnitine, made from amino acids, may help you age more gracefully. Found in every cell of our bodies (that’s how important it is), it’s particularly concentrated in the muscle cells. It makes energy so that we stay active and thrive throughout life. So, let’s dive into what this nutrient does and how it benefits the body.
What Does Carnitine Do?
As we mentioned, L-carnitine is made from other amino acids, specifically lysine and methionine. It ushers fat into the mitochondria (the engine of the cells) to help make energy for daily activities. It also helps remove toxins from the cell, helping keep mitochondria healthy, a key to slowing the aging process.
Carnitine is most concentrated in muscle and heart tissue to ensure there’s enough energy to keep you fueled. There are several different forms of carnitine, and each has a slightly different function. Some of these include (1,2):
- D-carnitine: An inactive form of carnitine, may increase the risk of deficiency because it interferes with absorption of the other types.
- Acetyl-L-carnitine: Best for brain health and function because it crosses the blood-brain barrier.
- Propionyl-L-carnitine: Used for blood pressure regulation because it increases a compound called nitric oxide, known to improve blood flow.
- L-carnitine L-tartrate: Most effective for improving exercise performance due to its speedy metabolism.
Each type of carnitine impacts health differently. Food contains a variety of forms of carnitine (or your body can make it), but if you want to take a supplement, you want to choose a specific type, dependent upon your goals.
Health Benefits of Carnitine
Research shows several additional health benefits of cartnitine. Most studies use acetyl-L-carnitine in their research because it’s the best absorbed and crosses the blood-brain barrier (3). A few of the research-backed benefits of carnitine include:
We all want to stay healthy later in life, but carnitine concentration in the muscles begins to decline with age. This leads to poor mitochondrial function, which contributes to the aging process, including memory loss (4).
Supplementation with acetyl-L-carnitine has been shown to slow the decline of the mitochondria, keeping them healthy and possibly slowing aging. Carnitine can also help improve memory function and maintain cognitive performance (5,6). Unfortunately, at this time, most of the research on aging and carnitine has been done on animals. Further research is needed to determine exact dosages for aging humans.
Blood Sugar Control and Diabetes
Insulin resistance is the triggering factor in the development of type 2 diabetes. Even if you don’t have diabetes, you still want to remain sensitive to insulin to help maintain blood sugar stability. It is believed that a defect in the ability to use fat for energy may worsen insulin resistance. This is where carnitine comes in: to help the body use the fat inside the muscle and lower glucose in the blood.
Research supports the theory that L-carnitine improves insulin sensitivity and blood sugar response after meals. It may do so by increasing the number of enzymes that help the body use carbohydrates more efficiently (7,8).
Diabetes can cause severe and debilitating symptoms for those with the disease. High blood sugar is toxic and causes damage to blood vessels, resulting in nerve problems, blindness, and kidney problems. Carnitine may help reduce the risk of certain side effects of diabetes, particularly nerve pain and neuropathy (9).
Carnitine may help improve and maintain heart health in a variety of ways. First, carnitine levels tend to be low in failing heart muscle, making it a critical component of keeping the heart healthy. Low levels of carnitine may worsen heart function.
Supplementation with L-carnitine could reduce risk of death from heart attacks by 27%, arrhythmias by 65%, and angina by 40%. (10) Carnitine may reduce blood pressure, and in turn, the risk of heart attacks, by lowering inflammation. Inflammation is responsible for many chronic diseases, not just heart disease (11).
Carnitine is concentrated not just in the muscles, but also in the area of the body where sperm matures and is stored. It is no surprise that carnitine has been found to improve male fertility by increasing sperm count and quality. It is believed that it boosts the ability of the mitochondria to produce energy so that it can be utilized to make more sperm and improve fertility.
A study of 100 men with low sperm motility and quality found that 3 grams of carnitine per day for four months significantly improved overall sperm health. Carnitine levels help evaluate fertility (13). Improvements in sperm health were only seen in those who already had problems with sperm function. Additional supplementation was not as beneficial for those who were already healthy. Further research is needed at this time to help evaluate an ideal dosage to help men struggling with infertility.
Cancer is a terrible disease with many debilitating symptoms. Carnitine deficiency is common in people with cancer, particularly for those undergoing treatment. Carnitine may help reduce the severity of some of these symptoms when used during radiation or chemotherapy.
Weight loss during cancer treatment is a major problem, putting those undergoing treatment at risk for severe complications. Carnitine depletion, associated with cancer, results in fatigue, muscle weakness, and a low tolerance for stress. Carnitine supplementation, through its anti-inflammatory support, helps improve the muscle wasting and weight loss commonly seen in cancer treatments (14).
Determining ideal dosages needs research for those undergoing cancer treatment, but the addition of 4g per day shows promise in improved fatigue and restored blood levels lowered by radiation and chemotherapy. It may also help improve sleep for people with cancer (15). Speak to a doctor about any kind of dietary supplement during cancer treatment.
Carnitine for weight loss seems to make a lot of sense since it helps the body burn fat for energy. But, studies show mixed results, and none show dramatic weight loss related to carnitine supplements.
One study evaluated the impact of L-carnitine on fat burning during a 90-minute cycling workout session. They found no change in the performance of the cyclists and no change in burned fat after four-weeks of taking a supplement (16). In another study, obese women took L-carnitine supplements and participated in an eight-week exercise program. This study showed no difference in the amount of fat lost between the control and the experimental groups (17).
However, other studies report that supplementation affects weight loss. A review of nine different studies found that people who took L-carnitine lost an average of 2.9 pounds more than those not using the supplement (18). The amount of additional weight lost isn’t huge, but it could make a difference over time (19).
Many fitness buffs take carnitine in an attempt to improve exercise performance, however, results are mixed. On one hand, it makes sense that carnitine improves performance due to energy production benefits, and you obviously need energy to exercise. Some evidence supports this use of carnitine due to an improvement in nitric oxide production, which helps increase blood flow and reduce fatigue while exercising. This means more sustained energy and less fatigue. It also speeds up recovery after a workout and protects against exercise-induced muscle damage (20,21).
Other research found no connection between carnitine supplements and an increase in oxygen use or improved muscle function during exercise. The reason: studies found that supplementation only increases blood levels of carnitine, not actual carnitine in the muscle where it needs to be for energy production during exercise (22). At this time, further research is needed to determine if carnitine supplements should be recommended to improve exercise performance and recovery.
How Much Carnitine Do I Need?
With a varied diet, the body makes all the carnitine it needs, somewhere between 11-34 mg/day. The ability to make it, in conjunction with the fact that the kidney preserves it if levels are low, means there’s no recommended amount needed per day. Carnitine isn’t well absorbed from dietary sources with only a 57-84% absorption rate. The rate from supplements, a mere 14-18% (23).
The liver and kidneys produce carnitine from two common amino acids, methionine and lysine. Methionine is found in: meat, nuts and cheese. Lysine is found in: meat, quinoa and tofu. Since the raw materials to make carnitine are widely available, even if you follow a vegetarian or vegan diet, it is unlikely that a deficiency will develop.
Food Sources of Carnitine
The word carnitine comes from the Latin word “carne” meaning meat. A few foods high in carnitine include (25):
- Beef, steak: 81 mg for 3 oz.
- Ground beef: 80 mg for 3 oz.
- Pork: 24 mg per 3 oz.
- Whole Milk: 8 mg per cup
- Fish, 5 mg per 3 oz.
- Chicken breast, 3 mg per 3 oz.
Although animal foods are the primary source of carnitine, the body makes it from other amino acids. So, you don’t need to worry about amounts, even if you’re vegan. Your body takes care of carnitine for you, provided you eat foods high in plant proteins.
Should you Take a Carnitine Supplement?
Supplementing in order to correct a potential deficiency is not necessary. But, some people do want to take a supplement for other potential benefits.
Carnitine supplements are popular in the athletic community in an attempt to help improve performance. Research conflicts about its ability to boost endurance and energy.
Supplemental carnitine may worsen symptoms of hypothyroidism, so avoid it if you experience thyroid issues. It also interferes with the effectiveness of certain medications. Get an evaluation from your doctor and test for individual medical conditions. Some reporting indicates potential toxicity. Doses of 3g or higher per day induced nausea, abdominal pain, vomiting and a “fishy smell” (26) in some people. Lower does don’t indicate these effects.
Stay below the upper limit of 3g per day to avoid side effects if testing carnitine for exercise purposes. The recommended dosage ranges from 500-2000 mg (0.5-2g) per day. Start taking a lower dose to see how your body reacts before increasing it to the higher level. Supplements come in liquid, capsules, or injectable form. Take oral carnitine with meals to help absorption. Always try food sources first before supplementing.
Acetyl-L-carnitine seems the best for absorption, even at high doses (up to 8 grams per day) with few side effects (25). It’s the form most commonly used in research and for improving brain and muscle function.