What Foods Are High in Methionine (L-Methionine) and What Is It Good For?

Methionine is an essential amino acid, one of the building blocks of protein. Foods high in methionine include eggs, meat, Brazil nuts, and other foods.

Methionine (L-methionine) is an amino acid, one of the building blocks of protein. It's also an essential amino acid, which means you must get it from food because your body can't make it. However, you don't need to be worried about getting enough.

You can get the methionine you need from complete proteins, which are usually animal products. You can also get methionine from a diet of varied plant foods.  

Although we call them building blocks, amino acids look more like long chains. The chains fold into shapes to make the different proteins the human body needs. 

There are over 20 amino acids that the body can arrange into proteins. Only nine are essential, meaning that you must get them from food. 

Scientists discovered that some amino acids are essential through laboratory studies with animals. They found rats fed only corn protein got sick, while those fed milk protein did not. They concluded that corn protein did not have all the elements rats need to stay healthy.  

Later, biologists purified amino acids and found that some of them were essential for human health. They also learned that humans in different stages of life had different amino acid needs.

Just as amino acids are building blocks of protein, proteins are building blocks for your body. Your bones, muscles, connective tissue, skin, hair, and nails all contain protein. 

Protein carries out important functions. About half of the protein you eat becomes enzymes, which control the chemical reactions of metabolism. Your red blood cells contain a protein that carries oxygen to all parts of your body. When your body is damaged, protein helps to rebuild it.

Humans need to consume protein every day. Your need for protein depends upon several factors, including your size. You need about seven grams of protein for every 20 pounds of body weight.

In parts of the world where food is scarce, many people are deficient in protein. Most people in the United States and other developed countries get plenty of protein.

Methionine is one of the two amino acids containing sulfur. The other one is cysteine, a nonessential amino acid. The body uses methionine to make cysteine. Researchers have set the recommended daily intake of methionine plus cysteine at 19 milligrams per kilogram of body weight, or about 8.6 milligrams per pound. Most people do not need to worry about that number. 

If you have enough protein in your diet, you are probably getting all the amino acids you need. That's why food labels give protein content, but they do not break the protein content down into amino acids. 

The best sources of methionine are animal products because they contain all the essential amino acids. Meat, fish, poultry, eggs, and dairy products are all complete proteins. If you prefer a plant-based diet, you can still get methionine and the other amino acids. Just eat a variety of plant foods every day. People once believed that you needed to take in all the amino acids in one meal, Scientists now say that it's okay to get your amino acids through the course of a day or two. 

A few plant foods, including soybeans, quinoa, and buckwheat, are complete proteins, but they may not contain as much protein as animal products. Soybeans belong to the class of foods called legumes, along with other beans, peas, lentils, and peanuts. Legumes are good sources of protein, but they are low in methionine. If you get your amino acids by eating plants, include other sources of protein besides legumes. 

Eggs and most meats are high in methionine with over 300 milligrams per serving. Brazil nuts have 315 milligrams in a 1-ounce serving. Plant foods with a medium amount of methionine include:

• Sunflower seeds
• Tofu
• Edamame
• Black beans
• Refried beans
• Cashews

These foods provide 100 to 300 milligrams of methionine per serving.

Where you get your amino acids may be as important as the amount. When you choose a protein-rich food, you get other elements, too. You may get unhealthy substances, like saturated fats and too much sodium. You can also get healthy nutrients like fiber and omega-3 fatty acids.

Eating red meat and highly processed meat may increase your risk of heart disease, diabetes, and some types of cancer. Long-range studies show getting protein from plants can increase your life span. 

People take methionine supplements for several health issues, including fatigue and liver problems. There is no proof that methionine improves these conditions. Methionine is seldom toxic, but very high doses could be dangerous.

You should not take supplements of any single amino acid for a long time. Such supplements can affect your metabolism. They can cause you to lose more nitrogen than you take in. They can make your kidneys work harder.

Some researchers have suggested that high levels of methionine could cause cardiovascular disease. That's because the body uses methionine to make cysteine, and high levels of homocysteine have been linked with heart disease. Researchers have not proven a cause-effect relationship between methionine levels and heart disease. Still, you should talk to your doctor before taking methionine supplements. 

If you are deficient in vitamin B6, vitamin B12, or folic acid, taking methionine supplements could cause cardiovascular problems. 

Methionine supplements can cause side effects, including:

• Irritability
• Nausea
• Vomiting
• Drowsiness
• Low blood pressure
• Dizziness

Some people should not take methionine. These include:

• Those with bipolar disorder
• Women who are pregnant or breastfeeding
• People with homocystinuria, a genetic disease that causes high levels of homocysteine

Doctors sometimes use methionine to treat acetaminophen overdoses. It may prevent the drug from damaging the liver.