L-Methionine: Benefits, Side Effects, Best Time to Take It & More

L-Methionine

(Methionine)

Evidence: Reasonable
Possible Benefits: Low
Safety: Low

What is L-methionine?

Methionine is one of 9 essential amino acids. Our bodies cannot synthesize this amino acid but need it to survive. As a supplement, L-methionine is often used for preventing birth defects. People also take the amino acid for liver disorders, viral infections, breast cancer, and other conditions, but there is not enough scientific evidence to support these uses. This article is about the main benefits of L-methionine, its potential side effects, the best time to take it, and more.

What does methionine do for the body?

Methionine is an essential amino acid, which means the body needs it to survive and cannot synthesize it.

Methionine is a “methyl donor” and plays an important part in the methylation process. Because of this, it can speed up or help maintain many chemical reactions in the body.

This amino acid acts as an antioxidant and helps protect damaged tissues.

Possible benefits

It is important to note that all of the potential benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.

Major benefits

Correcting a methionine deficiency – Since methionine is an essential amino acid, the body needs at least some amount to survive and function properly. Not getting enough methionine can lead to multiple health problems, including dementia. Fortunately, a deficiency in this amino acid is rare and shouldn’t happen unless you consume too low amounts of protein.

Minor benefits

Reduced birth defects – Eating more methionine during pregnancy can lower the risk of neural tube birth defects.

Possible side effects

These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.

Increased levels of homocysteine – Even low doses of methionine can elevate homocysteine levels in the blood. This is especially the case for people with impaired methylation.
Toxicity – Taking a very high dose of methionine at once could lead to severe brain damage and even death. While acute toxicity is rare, taking high amounts of L-methionine could lead to chronic toxicity and cause some health problems. To prevent chronic toxicity, it is best to stay below 500 mg a day unless you have a great reason to take more.
Amino acid imbalance – All essential and non-essential amino acids need to be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects without enough of another amino acid. That is most notably the case for glycine and methionine, but the principle applies to other amino acids, such as lysine and arginine, and the BCAA trio. Using a single amino acid supplement may lead to a negative nitrogen balance, which can lessen how well your metabolism works. A protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a specific amino acid/s.
Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.

Who should not take L-methionine?

You should probably avoid taking the supplement if you:

eat high amounts of protein from food (most whole foods contain at least some amount of each essential amino acid)
experience a severe adverse reaction after taking the amino acid
eat high amounts of muscle meat
do not get enough glycine

Who will benefit the most?

You should consider taking the supplement if you:

consume very little protein (less than 0.3 grams/pound of body weight)
take high amounts of glycine or TMG

How much L-methionine should you take?

The combined RDA (recommended daily allowance) for methionine and cysteine is 19 mg/kg/day for all adult men and most adult women. This is enough for the majority of people to prevent any symptoms of deficiency.

The RDA increases to 25 and 26 mg/kg/day for pregnant and lactating women, respectively.

Since these amino acids are in almost every food, you probably already get sufficient amounts from food alone. About 0.36 grams of protein/pound of body weight should be enough to prevent a deficiency.

If you plan to take L-methionine as a supplement, 200-500 mg appears to be the best daily target for most people. This amount should provide most of the benefits without meaningful side effects.

The upper safety limit for methionine is not well-established. To stay on the safe side, don’t take more than 500 mg daily unless you have a great reason to do so. Higher amounts may cause problems if you take the supplement for a prolonged period.

Food sources of methionine

Methionine is found in all whole foods that contain dietary protein.

The amount of L-methionine per gram of protein varies from food to food but a general rule of thumb is that the more protein you eat, the more methionine you are getting from food.

Beware that for optimal health you should get at least half a gram (preferably a full gram) of glycine for every gram of methionine.

This is generally the ratio people get from their diet. However, people who eat lots of muscle meat (the richest source of methionine) without getting enough glycine can throw this ratio off balance. This can cause long-term negative effects to their health.

The easiest way to find out exactly how much methionine, glycine, or other amino acids you are getting from food is with Cronometer.com. This free app allows you to track all vitamins, minerals, and more.

Best time to take L-methionine

Like most other amino acids, L-methionine is water-soluble, so you don’t have to take it with food to absorb it well. Taking the supplement with food is better if it causes stomach upset when you take it on an empty stomach.

To maximize the benefits, take L-methionine and other amino acids before or after a workout.

Whether you take the supplement in the morning or the evening doesn’t matter. It should not interrupt your sleep in any way.

If you practice time-restricted eating, take this amino acid during your eating window to guarantee it won’t break your fast.

Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.

Interactions

Glycine
For every gram of methionine, you need to consume at least half a gram of glycine if you wish to prevent side effects related to too much methionine. For optimal health, try to get about 1 gram of glycine for every gram of methionine.
Other amino acids
All essential and non-essential amino acids need to be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects without enough of another amino acid. That is most notably the case for glycine and methionine, but the principle applies to other amino acids, such as lysine and arginine, and the BCAA trio. Using a single amino acid supplement may lead to a negative nitrogen balance, which can lessen how well your metabolism works. A protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a specific amino acid/s.
TMG
Trimethylglycine (TMG) can greatly mitigate the side effects associated with methionine supplementation. For example, TMG is the most effective supplement we know of for lowering homocysteine levels.

Where to buy L-methionine

Amazon is the best option for ordering methionine supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.

Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.

FAQ

You can take the supplement daily and do not need to cycle it. However, it is certainly not a problem if you don’t take it daily. Not taking the supplement every once in a while could lead to better absorption. That is yet to be proven or disproven.

All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.

Yes. Most amino acids, including L-Methionine, absorb and digest well if you take them before falling asleep. The supplement should not impact sleep quality in any significant way.

This amino acid should not become harmful once it exceeds the expiration date but can lose potency over time.

Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months or even years.

While toxicity is rare, too much methionine in the system can cause some health problems, often related to causing an imbalance between methionine and glycine. It is best to stay below 500 mg a day to prevent these side effects.

You may need more of this amino acid if you:
– eat very little protein (less than 0.3 grams/pound of body weight)
– take high doses of glycine

The half-life of methionine in the body is 1.3-3.6 hours. This amino acid stays in your system for about 15 hours after you consume it.

In the long term, you need to take the supplement for about 2-4 weeks to begin noticing the benefits.

Amino acid supplements often come from animal products, but they do not have to be since all whole plant foods contain all essential amino acids. You can easily find vegan-friendly L-Methionine pills or powders but always check the label to be sure. If you buy the amino acid in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.

Like most other amino acids, methionine is water-soluble, so you don’t have to take it with food to absorb it well.

While low doses may not break a fast, higher doses certainly can. If you practice time-restricted eating, take this amino acid during your eating window so it doesn’t break your fast.

References

Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.

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