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Benefits | Foods | Recommended Daily Intake | Methionine and DNA | Methionine and Homocysteine | Side Effects

Amino acids help build proteins (there are also amino acids that do not synthesize proteins, such as taurine). In addition to this critical function, some amino acids have other specific roles.

Methionine is an amino acid that is metabolized into other important molecules in our body. These molecules are essential for proper cell function. Because of the important molecules it produces, some recommend increasing the intake of methionine from the diet. However, others recommend limiting methionine because of possible side effects and because of an important finding in animals: this amino acid is linked to premature aging.

Methionine is found in many proteins, both in food and in body tissues. In addition to being a building block for proteins, it has many other unique characteristics. One of these is its ability to be converted into important sulfur-containing molecules. Sulfur-containing molecules have a variety of functions, including protecting tissues, modifying DNA, and maintaining proper cell function.

For example, glutathione, which contains sulfur and is an important antioxidant in the body, is synthesized from glutamic acid, cysteine and glycine. Of the amino acids used to make proteins, only methionine and cysteine contain sulphur. Taurine also contains sulphur but is not found in proteins.

The body can produce the amino acid cysteine but methionine must come from the diet. Amino acids that cannot be synthesized by the body are called essential amino acids. Taurine is synthesized by the body but in limited quantities and so is considered by some to be a semi-essential amino acid.

Methionine: Benefits, Foods, RDI and Side Effects
Ball-and-stick model of the zwitterionic L-methionine molecule, C5H11NO2S, as found in the crystal structure. Source: Wikipedia

Methionine Benefits

  • Making New Protein in Cells – Methionine plays a key role in initiating the process of making new proteins in cells, [1] which happens continuously as older proteins decay. For example, it initiates the process of making new proteins in muscles after an exercise session that causes damage.
  • Eliminates Fat – Methionine is an essential amino acid that helps the body process and eliminate fat. It contains sulfur, a substance needed to produce the body’s most abundant natural antioxidant, glutathione.
  • Synthesizes Cysteine & Taurine – The body also needs the abundance of methionine to produce two other sulfur-containing amino acids, cysteine and taurine, which help the body eliminate toxins, build healthy tissues and promote cardiovascular health.
  • Helps liver process lipids – Methionine is a lipotropic or chemical that helps the liver process lipids. Other lipotropic substances are choline, inositol and betaine (trimethyl glycine), which help prevent fat accumulation in the liver and thus ensure its normal function, which is necessary to eliminate toxins from the body.
  • Regulates Glutathione – Methionine also supports liver function by regulating glutathione supplies. Glutathione is essential to help neutralize toxins in the liver.
  • Essential for the creation of Creatine – Methionine is essential for the creation of creatine, a nutrient found naturally mainly in muscle tissue that provides the energy the muscles need to be able to move and has been found to enhance athletic performance in short, intense workouts. Creatine is essential for all muscle function and therefore supports the normal functioning of the heart and circulatory system.
  • Essential for synthesizing collagen – Methionine is essential for the formation of healthy collagen used to form skin, nails and connective tissue and helps to reduce the level of inflammatory histamines in the body. People with conditions associated with excessive histamine production, such as arthritis and chronic allergies, can benefit from methionine supplements.
  • May help with Parkinson diseasePreliminary research suggests that methionine may also help treat symptoms of pancreatitis and Parkinson’s disease. It has also been found to be useful in treating urinary tract infections. Like cranberry (cranberry – a type of berry), methionine helps prevent bacteria from sticking and building up on the walls of the urinary tract. [2]

Foods containing Methionine

Methionine is an essential vitamin, which means it must be obtained through dietary sources. While almost all protein-containing foods have methionine, the amount varies widely. It is found in a variety of natural food sources, including

  • beans
  • eggs
  • fish,
  • garlic
  • lentils
  • meat
  • onions
  • soybeans
  • seeds
  • yogurt.

Methionine is also available in health stores and from online supplement stores in capsules form.

Some research has looked at the total amount of sulphur-containing amino acids (methionine and cysteine) in different types of diets. The highest intakes (6.8 grams per day) were reported in high-protein diets, while there were lower intakes for vegetarians (3.0 grams per day) and vegans (2.3 grams per day).

Despite the low intake among vegetarians, other research has shown that they actually have higher blood concentrations of methionine than those who eat meat and fish. This finding led researchers to conclude that dietary content and blood methionine concentrations are not always directly related.

The Featured Image. It shows some red Fish. Fish are a great source of Vitamin B12
– Fish are a good source of Methionine

Average-sized adults need about 800 to 1,000 milligrams of methionine per day. It is important to note that excessive methionine intake, combined with inadequate intake of folic acid, vitamin B6 and vitamin B12, can increase the conversion of methionine to homocysteine, a substance linked to cardiovascular disease.

However, supplementing up to 2 grams per day of methionine for long periods of time has not been reported to cause serious side effects.

Methionine and DNA

DNA contains the information that makes us who we are. Although much of this information may remain the same for our entire lives, environmental factors can change certain aspects of our DNA.

This is one of the most interesting roles of methionine because it can be converted into a molecule called SAM (S-Adenosyl methionine). SAM can change DNA by adding a methyl group, which is one carbon atom and three bonded hydrogen atoms (-CH3). [3]

The amount of methionine in the diet can affect the process of methylation but there are many unanswered questions. It is possible that increasing the amount of methionine in the diet may either increase or decrease how much certain aspects of DNA are changed as a result of the SAM effect.

In some cases there may be a benefit and in some cases a detriment. There is evidence that diets higher in nutrients that add methyl groups to DNA may reduce the risk of colon cancer. Other research has shown that higher methionine intake could worsen some conditions such as schizophrenia, perhaps because of the addition of more methyl groups to DNA.

Low-methionine diets extend lifespan in animals

Although methionine plays important roles in the body, some research shows benefits from diets that are low in this amino acid.

For example. some cancer cells depend on methionine for their growth [4]. In these cases, restricting dietary intake could be beneficial to ”keep cancer cells from having food”.

Since proteins from plants have a lower amount of methionine than animal proteins, some researchers believe that plant-based diets could be a tool to fight certain types of cancers.

Several animal studies show that reducing methionine in the diet may increase lifespan and improve health [5] [6].

Longevity might be attributed to enhanced stress resistance and metabolism, as well as the body’s ability to replicate cells. Low methionine levels have been found to decrease the process of aging in mice, according to this study.

Methionine And AIDS

People with AIDS have low levels of methionine. Although research in this area is preliminary, some researchers believe that methionine deficiency may be linked to certain aspects of the disease process, such as the deterioration that occurs in the nervous system that can cause dementia. One study reported that taking only 6 grams of methionine each day may improve memory recall in people with AIDS.

Methionine and Homocysteine

A concern associated with high methionine intake is that it can be converted to homocysteine, an amino acid associated with heart disease. High methionine intake can lead to an increase in homocysteine, although some individuals are more susceptible to this process than others.

Research suggests that the potential risks of high methionine intake are due to homocysteine, not to methionine itself. However, there are other factors that can alter homocysteine levels. For example, although they have a lower dietary intake of methionine, vegetarians and vegans may have higher homocysteine than omnivores due to low intake of vitamin B12.

Other research has shown that a diet high in protein and methionine did not increase homocysteine after six months, compared to a diet low in protein and low in methionine. Furthermore, changing intake by up to 100% did not appear to affect homocysteine in healthy adults without vitamin deficiencies.

Methionine Side effects

To assess the body’s responses to methionine, researchers give a large dose and observe the effects. This dose is much higher than the recommended intake, often about 100 mg per kilogram of body weight) or 6.8 grams for someone weighing 68 kg. This type of test has been done many times, with little side effects. Side effects include dizziness, drowsiness and changes in blood pressure.

A major adverse event occurred during one of these tests, resulting in the death of a person with high blood pressure. However, it seems likely that an accidental overdose of about 70 times the recommended intake caused the complications. [7]

Methionine is not particularly toxic to healthy people, except at extremely high doses that would be almost impossible to obtain through diet. Although methionine is involved in the production of homocysteine, there is no evidence that intake within a typical range is dangerous to heart health.

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