Imagine yourself as an older adult at an awesome retirement community, still being 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 choices you make with your diet today can impact how healthy you are as you age.
Obviously, there are many variables to staying healthy, but a substance called carnitine, made from amino acids may be able to help you age gracefully. This nutrient is found in every cell of our bodies (that’s how important it is)but is particularly concentrated in the muscle cells. It is needed to make energy so that we can 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. Its main role is helping bring fat into the mitochondria (the engine of the cells) to help make energy for day to day activities. It also helps remove toxins from the cell, helping keep mitochondria healthy, which is why it has been linked to slowing the aging process.
Carnitine is most concentrated in muscle and heart tissue to be sure that there is enough energy to keep you properly 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 as it is able to cross 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 ability to be metabolized quickly.
As you can see, each type of carnitine has a slightly different impact on health. Food contains a variety of forms of carnitine (or your body can make it), but if you want to take a supplement, you may want to choose a specific type depending on your goals.
Health Benefits of Carnitine
As you can see, carnitine has an important role in the body, but research has also identified several additional health benefits. Most studies use acetyl-L-carnitine in their research because it is best absorbed and is able to cross the blood-brain barrier (3). A few of the research-backed benefits of carnitine include:
We all want to say healthy as we age, but carnitine concentration in the muscles begins to decline as we get older. This leads to poor mitochondrial function, which is believed to contribute 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 to keep us healthy well into our old age.
Blood Sugar Control and Diabetes
Insulin resistance is the triggering factor for the development of type 2 diabetes. Even if you don’t have diabetes, you still want to remain sensitive to insulin to help maintain your blood sugar stable. It is believed that a defect in the ability to use fat for energy may worsen insulin resistance. This is where carnitine comes in, it may be able to help the body use the fat inside the muscle and lower glucose in the blood.
Research supports this theory, L-carnitine has been found to improve 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 can cause 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, meaning it is a critical component of keeping the heart healthy. Low levels of carnitine may worsen heart function.
But, supplementation with L-carnitine can help. It has been found to reduce risk of death by heart attacks by 27%, arrhythmias by 65%, and angina by 40%. (10) Carnitine also may potentially help reduce blood pressure, and in turn the risk of heart attacks, by lowering inflammation. Inflammation is believed to be the underlying cause of many chronic diseases also, not just heart disease. In addition, carnitine may also help improve symptoms of heart failure, leading to fewer deaths caused by this debilitating disease (11).
Carnitine is clearly very important for heart health, particularly for those already diagnosed with some type of illness. But, the evidence isn’t 100% supportive of it being a cure-all for the heart. A 2013 study found that supplementing with carnitine for a year increased the risk of heart attacks and stroke. The reason is that when taking carnitine this also increased the amount the amount of a substance called TMAO, linked to heart attacks. Gut bacteria seem to be to blame for increasing levels of this heart-damaging substance when provided with supplemental carnitine. They are able to convert it to TMAO. One thing to note, this study was an animal study, therefore we cannot draw conclusions yet on the impact it will have on humans (12). At this time, although some benefits have been seen with carnitine supplementation for heart health, the ideal dosage or the length of time of treatment is still not clear.
Carnitine is concentrated not just in the muscles, but also in the area of the body where sperm matures and is stored. So, 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 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 have also been used to evaluate fertility (13). But, it is important to note that improvements in sperm health were only seen in those who already had problems with their sperm function. Additional carnitine 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 relatively common in people with cancer, particularly for those undergoing treatment. Carnitine may be beneficial to help reduce the severity of some of these symptoms when used as a supplement 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 ability to work as an anti-inflammatory, has been shown to help improve the muscle wasting and weight loss commonly seen with cancer treatment (14).
Although further research is needed to determine ideal dosages of carnitine for those undergoing cancer treatment, the addition of 4g per day of carnitine has been shown to improve fatigue and restore blood levels that have been lowered by radiation and chemotherapy. It may also help improve sleep for people with cancer (15). At this time because cancer is such a serious and life-threatening illness, it is always best to speak to a doctor about any kind of dietary supplement during cancer treatment.
Carnitine has been recommended for weight loss since it is involved in helping your body burn fat for energy. Makes sense, right? But, studies have had mixed results and none have shown 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 how much fat was burned after four weeks of taking a supplement (16). In another study, obese women took L-carnitine supplements and participated in an 8-week exercise program. This study showed no difference in the amount of fat that was lost between the control and the experimental groups (17).
But, other studies have shown that supplementing with L-carnitine can make a difference for those trying to lose weight. A review of nine different studies did find that people who took L-carnitine lost an average of 2.9 pounds more than those who were not using the supplement (18). The amount of additional weight lost isn’t a huge amount when compared to the control group, but it could still make a difference over time. Other research has shown similar results, that supplementing with L-carnitine can moderately increase fat breakdown, even without any other changes to diet and exercise (19).
At this time, there is not enough evidence to conclude that increasing carnitine in intake through diet or supplements will make a big difference in trying to lose weight without any other additional effort, such as diet and exercise changes.
Many fitness buffs take carnitine in an attempt to improve exercise performance. But, the results on whether or not carnitine can help improve your workout are mixed. On one hand, it would make sense that carnitine can help improve performance since it is used to make energy and you obviously need energy to exercise. There is some evidence that supports this use of carnitine. It has been shown to improve nitric oxide production, which can help increase blood flow and reduce fatigue while exercising. These benefits may result in the ability exercise longer because you won’t get tired as quickly. It can also speed up recovery after a workout and protect against exercise-induced muscle damage (20,21).
Other research has found no connection between carnitine supplements and an increase in oxygen use or improved muscle function during exercise. The reason is that studies have found that carnitine supplementation only increases blood levels of carnitine. Supplementation does not increase actual carnitine in the muscle where it would need to be used 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 is able to make all the carnitine it needs, somewhere between 11-34 mg/day. The ability to make carnitine in conjunction with the fact that the kidney preserves it if levels are low means that there is no recommended amount you need per day. This is a good thing because carnitine isn’t that well absorbed from dietary sources anyway. Only about 57-84% of carnitine is absorbed from food, the rest is simply excreted. Absorption is even worse from supplements, with only about 14-18% being absorbed (23).
The liver and kidneys produce carnitine from two common amino acids, methionine and lysine. So, as long as you are consuming those you should be able to get enough carnitine. Lysine is found in a variety of foods, such as meat, quinoa, and tofu. Methionine is also found in many foods, such as meat, nuts, and cheese. 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.
In a few rare situations, such as genetic disorders or kidney failure, carnitine deficiency can occur. Pre-mature infants are also at risk for carnitine deficiency. Sometimes the protein that is required to take carnitine into the cells mutates, making it difficult for it to get to where it needs to go. This deficiency is very rare and needs to be treated by a doctor with therapeutic doses of carnitine. A few symptoms of deficiency include (24):
- Heart disease
- Low carnitine levels
- Loss of muscle
- Muscle weakness, particularly in the hips, shoulders, and legs
But, as we mentioned, this is really rare. Most of us have safety nets that protect our carnitine levels, since it is so important. No matter what type of diet you follow, as long as your kidney is working well, one of its jobs is to preserve carnitine. It does this by preventing excretion and storing it if necessary. As long as you are healthy generally healthy the body will be able to maintain carnitine levels will little effort. This is why there is no ideal recommended amount for this nutrient.
Food Sources of Carnitine
The word carnitine comes from the Latin word “carne” meaning meat. So, it is no surprise that carnitine is primarily found in animal foods. 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, as we mentioned, the body is able to make it from other amino acids. So, really you don’t need to worry if you are getting enough carnitine in your diet, particularly if you are choosing to follow a vegan diet. The body is so amazing it will take care of the carnitine for you, as long as you are eating foods high in plant proteins.
Should you take a carnitine supplement?
As we mentioned, the body is very good at making and conserving all the carnitine it needs. Even people following a vegan diet, who generally consume very little of this nutrient, have not been found to develop carnitine deficiency. Therefore, 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. But, as we mentioned, the research is still conflicted about its ability to boost endurance and energy. Another reason it is commonly used is to promote weight loss. But, it is unclear if taking carnitine supplements actually boost weight loss or fat burning in any significant way. So, if you are expecting to lose 20 pounds by just popping a pill, sorry to break it do you, that is pretty unlikely. There is no “magic bullet” for weight loss.
There may also be some side effects of taking carnitine supplements. Supplemental carnitine may worsen symptoms of hypothyroidism, so should be avoided if you have been diagnosed with thyroid issues. It can also interfere with the effectiveness of certain medications. As with any supplement, it is best to ask your doctor before starting so they can evaluate its safety for your individual medical conditions. There are also some reports of potential toxicity. Doses of 3g or higher per day have been found to cause nausea, abdominal pain, vomiting and a “fishy smell” (26). These side effects have not been reported at lower dosages.
On the other hand, there are certain groups of people who might benefit from a carnitine supplement. Those who are vegan or vegetarian tend to not get much carnitine from food, although overt deficiencies have not been found, a little extra carnitine might be beneficial (27). Older adults also tend to not eat as much meat and carnitine levels decrease as we age. Supplementation with 2g of L-carnitine was found to reduce fatigue and improve muscle function in older adults (28). Finally, those with serious illnesses such as liver or kidney failure and cancer may also benefit from supplementation as these conditions increase the risk for deficiency. If you or a loved one has been diagnosed with any of these illnesses, ask a doctor for recommended dosages (29).
If you do want to take a carnitine supplement, to see if it helps your exercise performance or for another health concern, it is best to say below the upper limit of 3g per day to avoid side effects. After all, who wants to smell like fish? The recommended dosage is anywhere from 500-2000 mg (0.5-2g) per day. Start with taking a lower dose to see how your body reacts before increasing it to the higher level. Supplements are usually found in liquid, capsules, or in an injectable form. If you are taking oral carnitine, be sure to take it with meals to help with absorption. But, remember supplemental carnitine is poorly absorbed, so really you are best getting your carnitine from food directly by including high protein foods in your diet.
As we mentioned, there are different forms of carnitine, depending on your health goals. Acetyl-L-carnitine seems to be best absorbed and has been given at high doses (as much as 8 grams per day) with few side effects (25). It is the form most commonly used in research and can help improve brain and muscle function.
Overall, we know carnitine has many benefits for our health, but further research is needed to help determine if it is necessary as a daily supplement. Since deficiencies have not been identified in healthy people with varied diets, it is probably best to avoid additional carnitine in supplement form, unless it is recommended by a doctor. Your body is amazing, it can make such an important nutrient from the raw materials you provide through food. Our recommendation would be to always aim to use real food as the best way to meet your nutrient needs. A balanced will support your dreams of a healthy and active life well into old age.