When protein is in food the food, your digestive system breaks it down into amino acids, and your body uses these to manufacture hundreds of new proteins needed by all your cells. Two amino acids, called cysteine and methionine, are unusual because they contain the element sulfur, which plays an important role in determining the shape of new proteins by helping these compounds fold. Many common foods are good sources of both these amino acids.
Meat and Poultry
Animal-based foods are generally good sources of both methionine and cysteine 2. For example, a serving of lean beef loin that weighs about 6 ounces provides 1,270 milligrams of methionine and 470 milligrams of cysteine, while a similar-sized serving of a pork chop that's trimmed of fat contains about 1,145 milligrams of methionine and 460 milligrams of cysteine. Other meats such as lamb and game meats are also good sources. Poultry is also rich in both amino acids, with 1 cup of roasted and chopped chicken breast meat providing about 1,200 milligrams of methionine and 550 milligrams of cysteine.
Fish and Seafood
Most fish and certain types of seafood are also good sources of methionine and cysteine. Other common types of fish, such as:
- are also good sources of both amino acids
Eggs and Dairy Products
Dairy products are also good sources of both amino acids 4. Other cheeses, such as cheddar, Parmesan and mozzarella, are also rich in both compounds. Milk provides both amino acids in slightly lesser amounts. For example, 1 cup of nonfat milk provides about 200 milligrams of methionine and 50 milligrams of cysteine. Eggs are also a good source, with about 190 milligrams of methionine and 135 milligrams of cysteine in 1 large cooked egg.
If you follow a vegetarian diet, some types of plant-based foods are also good sources of methionine and cysteine. Many types of nuts provide these nutrients, including Brazil nuts, which have about 65 milligrams of methionine and 245 milligrams of cysteine in 1/2 cup.
- ValentynVolkov/iStock/Getty Images