What Is Methionine?

An Essential Amino Acid for Healthy Skin, Hair, Nails, and More

Methionine is an essential amino acid found in protein food sources and 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 mg daily per kilogram of body weight from the food you eat.

Woman taking medicine
Tassii / Getty Images

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, as well as side effects, precautions, suggested dosage, and food sources of this essential amino acid.

Dietary supplements are not regulated in the United States, meaning the FDA does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLabs, or NSF. However, even if supplements are third-party tested, that doesn’t mean that they are necessarily safe for all or effective in general. It is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

●     Active Ingredient(s): L-methionine

●     Alternate Name(s): L-methionine, D-methionine, DL-methionine, L-2-amino-4-(methylthio) butyric acid

●     Legal Status: Legal in the US and sold over-the-counter

●     Suggested Dose: No standard dose for methionine exists.

●     Safety Considerations: Methionine has potential side effects including dizziness, upset stomach, and drowsiness. It is possible to overdose on methionine.

Uses of Methionine

Methionine is considered an essential amino acid because it must be consumed through 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.

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

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, over-the-counter 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 in the treatment of 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

A 2013 meta-analysis concluded 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 the production of 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 looking at 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 inhibits cancer cell growth is growing. There are thoughts that methionine restriction could be used as part of cancer treatment.

More human trials are needed to confirm whether methionine supplementation or methionine restriction would be beneficial for cancer risk reduction.

Liver Damage

Methionine may be beneficial for liver damage, especially when used alongside other treatments.

A recent review that looked at its role in liver damage found that supplementing with methionine may help reduce the risk of liver damage. Methionine supplementation may help increase levels of S-adenosyl methionine (SAMe) which may be protective against liver damage.

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

Parkinson's Disease

It has been suggested that methionine may be used to treat Parkinson's disease. However, the only evidence supporting this claim comes from a lab. And while we can learn from lab studies, results need to be replicated in humans.

In one such lab study, methionine was found to produce protective effects against the development of Parkinson's disease. Researchers concluded that a methionine-rich diet may protect aging neurons from oxidative stress and dysfunction, two factors that could lead to neurodegenerative diseases, like Parkinson's.

Other 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 common or severe.

Common Side Effects

Common side effects associated with methionine tend to be mild.

  • 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 have a discussion with their healthcare provider before taking it.

People with methylenetetrahydrofolate reductase (MTHFR) deficiency, a hereditary disease, should avoid using methionine. People with MTHFR deficiency are unable to 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 levels of homocysteine 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. Although, the research looking into this claim is not strong. One animal study correlated methionine use to behavioral responses and symptoms similar to schizophrenia.

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

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?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage is appropriate for your individual needs.

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 mg/kg 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 the condition that is being treated as well as other factors like your age and gender. 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 common side effects. It can happen over time with a build-up of methionine or after one large dose of methionine.

At normal doses, methionine is thought to be safe for most people to take. However, according to research methionine can be toxic at very high doses. 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 for certain if 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 the ingredient list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss any 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 it 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 benefits. 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 be able to help remove lead from the body, something that chlorella may also do. However, research surrounding these claims is limited.
  • Like methionine, folate may be a useful supplement for those with Parkinson's disease. Studies have shown that Parkinson's disease patients with folate deficiency may have higher rates of cognitive dysfunction.

Talk with your healthcare provider if you're not sure 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 wen 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:

As you may be able to tell, many of these foods are proteins, which makes sense because methionine is used to make proteins. It has also been suggested that cooking methionine-containing foods at high temperatures may increase their bioavailability.

Typically, a well-balanced diet that contains a variety of 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 tend to also be sold as capsules.

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

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 supplements are not regulated by the FDA, those that have been 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.

Methionine is one of just two amino acids that contain sulfur and may be beneficial for many health concerns. However, research that backs up most of these health claims is lacking.

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

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

Frequently Asked Questions

  • Is methionine safe for infants or children?

    Methionine may be safe for infants and children, but be sure to consult your child's healthcare provider before use. 


    Adverse events have not been reported in studies looking at methionine use in infants and children. However, this research is limited.

  • Which food sources are highest in methionine?

    Many foods contain methionine, making it easy for you to get all you need from your diet.

    Methionine is found in the greatest amounts in animal foods, like beef, poultry, pork, eggs, and seafood. It is also present in plant-based foods like nuts, seeds, soy, beans, and some vegetables.

  • Do vegetarians need to take methionine supplements to get enough sulfur in the diet?

    Since methionine is found in plenty of plant-based foods, vegetarians do not necessarily need to take methionine supplements to get enough sulfur.

    If you are a vegetarian (or non-vegetarian), you should only take methionine supplements if directed to do so by your healthcare provider. A methionine supplement may be necessary in the case of a deficiency, but this is rare.

15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. PubChem. Methionine.

  2. Park BK, Dear JW, Antoine DJ. Paracetamol (acetaminophen) poisoning. BMJ Clin Evid. 2015;2015:2101.

  3. Zhou ZY, Wan XY, Cao JW. Dietary methionine intake and risk of incident colorectal cancer: a meta-analysis of 8 prospective studies involving 431,029 participantsPLoS One. 2013;8(12):e83588. Published 2013 Dec 10. doi:10.1371/journal.pone.0083588.

  4. Wanders D, Hobson K, Ji X. Methionine Restriction and Cancer BiologyNutrients. 2020;12(3):684. Published 2020 Mar 3. doi:10.3390/nu12030684.

  5. Li Z, Wang F, Liang B, et al. Methionine metabolism in chronic liver diseases: an update on molecular mechanism and therapeutic implication. Signal Transduct Target Ther. 2020;5(1):280. Published 2020 Dec 4. doi:10.1038/s41392-020-00349-7.

  6. Catanesi M, Brandolini L, d'Angelo M, et al. L-Methionine Protects against Oxidative Stress and Mitochondrial Dysfunction in an In Vitro Model of Parkinson's DiseaseAntioxidants (Basel). 2021;10(9):1467. Published 2021 Sep 15. doi:10.3390/antiox10091467.

  7. Cottington EM, LaMantia C, Stabler SP, et al. Adverse event associated with methionine loading test: a case reportArterioscler Thromb Vasc Biol. 2002;22(6):1046-1050. doi:10.1161/01.atv.0000020400.25088.a7.

  8. NIH - National Library of Medicine - National Center for Biotechnology Information. Methylenetetrahydrofolate Reductase Deficiency.

  9. Medline Plus. Homocysteine Test.

  10. Wang L, Alachkar A, Sanathara N, Belluzzi JD, Wang Z, Civelli O. A Methionine-Induced Animal Model of Schizophrenia: Face and Predictive ValidityInt J Neuropsychopharmacol. 2015;18(12):pyv054. Published 2015 May 19. doi:10.1093/ijnp/pyv054.

  11. ME, Han B, . Are we getting enough sulfur in our diet?. Nutr Metab (Lond). 2007;4:24. doi:10.1186/1743-7075-4-24.

  12. Garlick PJ. Toxicity of methionine in humansJ Nutr. 2006;136(6 Suppl):1722S-1725S. doi:10.1093/jn/136.6.1722S.

  13. Zhai Q, Narbad A, Chen W. Dietary strategies for the treatment of cadmium and lead toxicityNutrients. 2015;7(1):552-571. Published 2015 Jan 14. doi:10.3390/nu7010552.

  14. Xie Y, Feng H, Peng S, Xiao J, Zhang J. Association of plasma homocysteine, vitamin B12 and folate levels with cognitive function in Parkinson's disease: A meta-analysisNeurosci Lett. 2017;636:190-195. doi:10.1016/j.neulet.2016.11.007.

  15. Science Direct Topics. Methionine.

Additional Reading

By Sherry Christiansen
Sherry Christiansen is a medical writer with a healthcare background. She has worked in the hospital setting and collaborated on Alzheimer's research.