What Is Methionine?

Methionine is an essential amino acid found in protein food sources such as meat and dairy. Your body cannot make methionine, so you must get it from food or supplements. It is important for many functions in the body, including building new proteins, making DNA, and normal tissue growth and repair.

There is no suggested dose for methionine supplements, but you should get about 14 milligrams (mg) daily per kilogram (kg) of body weight from the food you eat.

Methionine supplements are commonly taken to treat various infections and disorders, but there is limited scientific research to support these uses. However, methionine is thought to be effective in treating Tylenol (acetaminophen) poisoning.

There is some concern that methionine supplements may cause more harm than good, as taking too much of it has been associated with various side effects.

This article will explore the evidence-based uses of methionine, side effects, precautions, suggested dosage, and food sources of this essential amino acid.

Purported Uses of Methionine

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietician, pharmacist, or a healthcare provider. No supplement is intended to treat, cure, or prevent a disease.

Methionine is considered an essential amino acid because it must be consumed from the diet. Our bodies cannot produce it.

There are two types of methionine: L-methionine (which is naturally occurring and usually found in supplements) and D-methionine. Each contains the same chemical makeup, but the molecules are mirror images. A mixture of the two is called DL-methionine.

Methionine may be beneficial for various health conditions. However, many of these are not well-supported by scientific evidence. Below is a look at some of the better-supported uses of methionine.

Acetaminophen Overdose

One of the leading uses of methionine is in the treatment of an acetaminophen overdose.

Acetaminophen, or Tylenol, is a common, OTC pain reliever. If a person takes too much acetaminophen, then swift action is needed to prevent liver damage or even possible death.

Oral methionine taken within 10 hours has been used to treat acetaminophen overdose. Methionine is thought to prevent the byproducts of acetaminophen from damaging the liver as a result of an acetaminophen overdose.

However, it should be pointed out that there are other treatment options and that methionine may not be the most effective one for an acetaminophen overdose.

Cancer Risk

Methionine has been studied for its role in cancer risk. However, the results are conflicting.

A 2013 meta-analysis suggested that consuming dietary methionine may be associated with a decreased risk of colon cancer. Researchers believed this decreased risk may be due to methionine's role in producing S-adenosyl methionine (SAMe). Lab and animal studies have shown that SAMe may be able to reduce inflammation, inhibit various cancer pathways, and even cause cancer cell death. 

However, these findings have not always been replicated in studies examining the relationship between methionine and cancer. In fact, some studies have shown that methionine restriction may lead to a lower risk of cancer.

A review from 2020 noted that methionine is an integral piece of growth in certain types of cancer cells. According to the review, evidence that methionine restriction may inhibit cancer cell growth is growing.

More human trials are needed to confirm whether methionine supplementation or methionine restriction would be beneficial for cancer risk reduction. Until then, methionine should not be used for this purpose.

Liver Damage

Methionine may help improve liver damage, especially when used alongside other treatments.

A recent review examining its role in liver damage found that methionine supplementation may help reduce the risk of liver damage. Methionine supplementation may help increase levels of methionine SAMe, which may protect against liver damage.

However, these findings may be controversial. And, once again, stronger research is needed to support this claim.

Other Purported Uses

Methionine is thought to have other potential benefits, including:

• Nourishing the hair, skin, and nails
• Slowing down cell aging
• Protecting cells from pollutants
• Helping with the absorption of other nutrients, like selenium and zinc
• Aiding in the detoxification of heavy metals, including lead and mercury
  

However, like many of the potential uses of methionine, the research supporting these health claims is limited.

What Are the Side Effects of Methionine?

Side effects are always possible when taking supplements, and methionine is no exception. Methionine side effects can be mild or severe.

Common Side Effects

Common side effects associated with methionine tend to be mild and include:

• Nausea
• Vomiting
• Drowsiness
• Irritability

The best way to avoid side effects as much as possible is to take methionine supplements as directed. Oftentimes, side effects are more likely when supplements are taken incorrectly or if the dose is too high.

Severe Side Effects

In general, methionine is thought to be safe. However, severe side effects are possible if it is taken incorrectly. These may include blood pressure changes, disorientation, and tachycardia, or increased heart rate. Although extremely rare, it is possible to overdose on methionine.

Precautions

Methionine may not be safe for everyone. Certain populations should avoid using methionine or at least discuss it with their healthcare provider before taking it.

People with methylenetetrahydrofolate reductase (MTHFR) deficiency, a hereditary disease, should avoid using methionine. People with MTHFR deficiency cannot convert homocysteine, a potentially dangerous compound, to methionine. For people with MTHFR deficiency, taking methionine supplements may cause homocysteine levels to become too high.

Similarly, people with high homocysteine levels in their blood should avoid using methionine supplements. High blood homocysteine can lead to heart disease and other complications.

It has also been suggested that methionine could make schizophrenia worse for some people. However, the research looking into this claim is not strong. One animal study correlated methionine use to behavioral responses and symptoms similar to schizophrenia. It is unknown if these results translate to humans.

There is not enough information to know if methionine is safe for people who are pregnant or breastfeeding. Therefore, it is recommended to avoid taking it during pregnancy and breastfeeding.

To better understand these and other precautions, talk with your healthcare provider about whether methionine is safe for you.

Dosage: How Much Methionine Should I Take?

There is no standard dose for methionine supplements. However, there is a recommended daily intake of methionine from food and other sources.

The Recommended Daily Allowance (RDA) for adults for either methionine or cysteine (the other sulfur-containing amino acid) is 14 milligrams/kilogram of body weight. Using this math, a 154-pound person would need 1.1 grams of methionine or cysteine per day. You need this amount from either methionine or cysteine each day to get all the sulfur your body needs to build important proteins.

The right dosage for you may depend on several factors, such as your current health, age, and sex. Be sure to talk with your healthcare provider about using methionine safely.

What Happens If I Take Too Much Methionine?

If you take too much methionine, you may experience toxicity or even an overdose.

Methionine toxicity may cause severe or mild side effects. It can happen over time with a build-up of methionine or after one large dose of methionine.

Methionine is thought to be safe for most people to take at normal doses. However, according to research, methionine can be toxic at very high doses. In addition, taking too much methionine can cause homocysteine levels to rise, which can result in issues with heart function.

Methionine overdose is extremely rare but possible. In one extreme case, a study participant was accidentally given a methionine dose that was substantially higher than it should have been. This overdose resulted in death in this case.

Interactions

Interactions with methionine are not well-documented. This means we do not know whether any medications or supplements negatively interact with methionine.

Regardless, it is always best to be on the safe side.

You can be safe by carefully reading a supplement's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

How to Store Methionine

Improper storage of methionine supplements can cause spoiling. Methionine should be stored in a cool, dry place that is not in direct sunlight. It is best to keep methionine supplements in the air-tight container they came in.

Methionine supplements should be discarded once they reach the expiration date listed on the packaging.

Due to the possibility of overdose, keep methionine supplements out of reach of pets and small children.

Similar Supplements

Some supplements may work similarly to methionine when it comes to potential uses. These include:

• Cysteine is the only other amino acid that contains sulfur. Because of this, it may act similarly to methionine. If you have been told that you need more sulfur in your diet, you may be able to use either methionine or cysteine to do so.
  
• Methionine may help remove lead from the body, something that chlorella may also do. However, research surrounding these claims is limited.

Talk with your healthcare provider if you are unsure which supplement is best for you.

Sources of Methionine & What to Look For

In most cases, you can get all the methionine you need from food sources. Methionine is found in many different types of food, making it easy to add to your diet. Plus, nutrients from food are often better absorbed than when they come from supplements.

However, some people may need to use a methionine supplement for various health reasons.

Food Sources of Methionine

Methionine is prevalent in many foods. It can be found in both vegan and non-vegan food sources.

Food sources of methionine include:

• Eggs
• Chicken
• Beef
• Pork
• Milk
• Corn
• Lobster (tail)
• Fish (canned tuna)
• Oatmeal
• Beans
• Cauliflower

As you may be able to tell, many of these foods are proteins, which makes sense because methionine is used to make proteins. Typically, a well-balanced diet containing various fruits, vegetables, grains, healthy fats, and lean protein will provide you with all the methionine and other nutrients your body needs.

Methionine Supplements

Methionine supplements are available in capsule form. You may also find supplements that contain methionine and other nutrients, like various amino acids. These also tend to be sold as capsules.

Vegan versions of methionine supplements are available. If you are vegan or vegetarian, choose a plant-based methionine supplement.

It is best to select a methionine supplement that has been certified by a third party, like U.S. Pharmacopeia, NSF International, or Consumer Lab. Since the FDA does not closely regulate supplements like drugs, those certified are more likely to contain the ingredients they say they do.

Summary

Methionine is an essential amino acid, which means we must consume it. It is one of just two amino acids that contain sulfur and may be helpful for some health concerns. However, research that backs up most of these health claims is lacking.

There are few side effects associated with taking methionine, but it is important to take precautions when using it, as an overdose is possible.

Methionine supplements are not suitable for everyone, so talk with your healthcare provider before starting methionine supplements for additional information.