Overview

Methionine is an essential amino acid that your body needs to function. Since your body cannot make methionine on its own, you must get it from your diet. Methionine dietary supplements appear to be well tolerated and are sometimes used to improve overall health. However, most people in the U.S. get enough methionine from their diets, and the benefits of supplements are not well defined. Before taking methionine, tell your health care provider about all of your health conditions and any medicines or supplements you may be using.

Uses

What is methionine used for?

Methionine supplements may be used to improve overall health, but their benefits are not well defined.

Note: The FDA has not reviewed methionine for safety and effectiveness. Learn more about dietary supplements here.

How does methionine work (mechanism of action)?

Methionine is an amino acid, which is a building block for protein. Your body uses methionine to make protein and other important substances that have effects in the body.

Your body needs methionine to function, but it cannot make methionine on its own. As a result, you must get this amino acid from your diet. Methionine is found in protein-rich foods, including meat, cheese, eggs, fish, and beans. Most people in the U.S. get enough methionine from their diet, but it is also available in dietary supplements. Product labels may list methionine as L-methionine, which is the same thing.

S-adenosylmethionine (SAMe) is one of the chemicals that your body makes from methionine. After your body converts methionine into SAMe, it uses SAMe to make other chemicals that your organs need to function. Some examples include glutathione (an antioxidant that helps keep your liver healthy) and important brain chemicals called neurotransmitters. But it is not clear if methionine supplements increase the levels of SAMe in your body. The benefits of methionine supplements for improving brain or liver health are unclear.

When your body turns methionine into other substances, such as SAMe, it creates a chemical called homocysteine. Although small amounts of homocysteine are safe, having high levels over time may increase your risk for certain health issues. Research shows that taking very high doses of methionine, such as 6 grams or more per day, can cause your homocysteine levels to increase by a large amount. But this dose of methionine is not available in foods, and methionine is a safe and important part of your diet. Most methionine supplements, when taken as recommended on the product label, also do not provide high enough doses to increase homocysteine levels or cause health problems.

How should I store methionine?

You should store methionine according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of methionine?

Methionine seems to be well tolerated. Tell your health care provider if you have any side effects that bother you.

There may be side effects of methionine that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of methionine?

While less common, the most serious side effects of methionine are described below, along with what to do if they happen.

Severe Allergic Reactions. Methionine may cause allergic reactions, which can be serious. Stop taking methionine and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Precautions

Who should not use methionine?

Allergies to Ingredients. People who are allergic to any of the following should not take methionine.

• Methionine
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific methionine products they stock.

Low-Methionine Diet. If your health care provider has told you to follow a low-methionine diet for any reason, you should not take methionine supplements.

What should I know about methionine before using it?

Methionine is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep methionine out of the reach of children.

The FDA has not tested methionine products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using methionine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if methionine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions.Tell your health care provider if you have any of the following.

• Liver problems
• Mental health problems, including schizophrenia

Pregnancy. It is not known if or how methionine could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if methionine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does methionine interact with foods or drinks?

There are no known interactions between methionine and foods or drinks.

It is unknown if drinking alcohol will affect methionine.

Does methionine interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are taking multivitamins or supplements that contain vitamin B6 (pyridoxine), vitamin B9 (folic acid), vitamin B12 (cyanocobalamin), or vitamin C.

The interactions between methionine and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with methionine is incomplete. Always check with your health care provider before taking methionine with any medicines.

Dosing

What should I do if I accidentally use too much methionine?

If you or someone else has used too much methionine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Methionine is naturally found in foods that contain protein and is also available as a dietary supplement.

Read the product label closely, and speak with a health care provider about how to take methionine safely. Do not take double or extra doses, even if you miss a dose.