Methionine does a lot more than build protein. This amino acid helps produce substances that support your metabolism, and it's especially vital for synthesizing a powerful antioxidant called glutathione. It's an essential amino acid, meaning it must be obtained through your diet because your body can't make it. But if you plan a varied menu with protein-rich foods, such as meats and poultry, and veggies, such as corn, spinach and broccoli, you should easily meet your daily methionine requirement.
Methionine is one of only a few sulfur-containing amino acids, which is an important distinction because sulfur influences the way it works. It helps synthesize two substances: S-adenosylmethionine, or SAMe, and glutathione. SAMe supports many metabolic activities throughout your body, reports the University of Maryland Medical Center. It maintains cell membranes, strengthens your immune system and is essential for production of the mood-regulating neurotransmitter serotonin. Glutathione works as an antioxidant, protecting cells from reactive molecules -- free radicals -- that can damage them. Methionine also helps prevent diet-induced fatty liver disease, according to the June 2014 issue of the scientific journal “Molecules.” Glutathione can also be made from another sulfur-containing amino acid called cysteine.
Top Food Sources
You’ll get the most methionine from meat, poultry and fish because they're rich in protein, which contains methionine. One of the best sources is beef sirloin roast, a lean meat that provides 0.8 gram of methionine in a 3-ounce serving. Other good sources include skinless chicken breast, salmon and tuna. Beans contain more methionine than most plant-based foods. One cup of cooked soybeans or a similar amount of beans, such as kidney, white or black beans, has about 0.2 gram of methionine.
Other Good Choices
Dairy foods are good sources of methionine, with about 0.2 gram in 1 cup of low-fat milk or yogurt. A 1-ounce serving of sesame seeds, hazelnuts or pecans contains about 0.1 gram, reports the U.S. Department of Agriculture. Some vegetables to choose from include a baked potato and 1-cup servings of lima beans, sweet corn, spinach and broccoli. They all provide about 0.1 gram of methionine per serving.
Methionine and cysteine are closely linked in metabolic pathways and they're paired together for their recommended dietary allowance amount. Healthy adults should consume 19 milligrams of methionine and cysteine daily for every 2.2 pounds of body weight. Check with your doctor before taking methionine supplements. Methionine is converted into homocysteine, and consuming more than five times the recommended amount of methionine may boost the levels of homocysteine in your blood, according to a report in the “Journal of Nutrition” in 2006. When homocysteine stays high for a long time, it can damage your arteries and increase the risk of cardiovascular disease.