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L-Cysteine can be found in a number of foods, including cheese, yogurt, meat (pork, chicken, turkey and duck), wheat germ and oats. L-Cysteine is a form of the semi-essential amino acid cysteine.
“Semi-essential” means that your body normally produces enough of the amino acid, but sometimes supplementation is required.
In periods of good health, L-cysteine is naturally produced in the body using the amino acid methionine. However, acute periods of stress and illness may decrease the amount of L-cysteine the body is able to make. In these situations, it is important to eat a healthy diet rich in L-cysteine food sources.
L-cysteine can be consumed by eating a diet high in cystine, another amino acid that is made of two cysteine molecules. We can increase the amount of L-cysteine we are receiving in our diets by choosing foods high in cystine. This compound is metabolized in the body to produce two molecules of cysteine.
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The amino acid L-Cysteine is involved in protein synthesis and plays a role in the maintenance of body tissues like skin, nails and hair.
L-Cysteine is also a precursor of the antioxidant glutathione.
Nutrient labels usually list the amount of cystine in food instead of L-cysteine (or cysteine).
Thus, when looking for L-cysteine food sources, look for the ingredient cystine instead.
Dietary Sources of L-Cysteine
Poultry: One of the best dietary sources of cystine is poultry. In particular, turkey has a high content of the amino acid: a recommended 3 oz. serving of turkey contains 2.5 g of cystine. Chicken, goose and pigeon are also good sources.
Eggs: Eggs are a great source of cystine, be they fresh, separated, or dried. Most of the protein contained in eggs is found in the egg white. Because protein is composed of amino acids, the protein in eggs is a good source of L-cysteine.
Egg whites can be purchased dried or in a Tetra Pak carton to extend the shelf life. One cup of dried egg white powder can contain up to 2.5 g of cystine. One whole egg can contain as much as 2 g of cystine.
Soy: Soy has become a popular meat alternative in recent years. Meats are considered a complete protein because they contain all essential and conditionally essential amino acids. In contrast, plant proteins are often incomplete and must be paired with other protein sources. Soy is an exception to this rule because it contains all 20 amino acids, including cystine and L-cysteine.
Half a cup of uncooked soybeans can contain as much as 7 g of cystine. Roasted soybeans contain slightly less L-cysteine because cooking can denature proteins and amino acids. Nevertheless, roasted soybeans still have as much as 5 g of L-cysteine per half-cup serving. Soy flour is also a great L-cysteine food source: for every cup of soy flour used in a recipe, there is approximately 8 g of L-cysteine.
Grains: Vegetarians often pair different grains together to get the recommended daily dose of essential amino acids. As with all grains, it is best to look for whole versions to get the most nutrients, including fats, fiber, vitamins and minerals.
One cup of oats can contain up to 7 g of cystine. Cereal grains, such as barley, oat bran, durum wheat, spelt, red winter wheat and triticale, also contain good levels of cystine.
A great way to add vegan L-cysteine to your lunch or dinner is to make a couscous salad or use this nutrient-packed grain as a substitute for rice.
L-Cysteine and Stress
Eating a diet rich in cysteine food sources is especially important during periods of high stress.
In acute periods of stress the body does not operate optimally and conditionally essential amino acids may not be adequately synthesized. In this case, stress may lead to illness.
If L-cysteine is not sufficiently manufactured by the body, eating a diet high in cystine is important. Individuals may also opt to take L-cysteine supplements.
In supplement form, L-cysteine is consumed as N-acetyl-L-cysteine (NAC). The body converts NAC into cysteine and then into the antioxidant glutathione.
There are several brands of NAC on the market. NAC tablets and capsules usually come is doses of 500 mg. This dose is closely related to the doses of L-cysteine found in food. A capsule may be taken two-to-three times per day, as food would normally be taken. This is only a general guideline and the label instructions of the supplement should always be followed.
Conclusions
There are several benefits to ensuring L-cysteine is present in our diets, whether in the foods we eat or the supplements we take.
L-cysteine is generally well tolerated when taken as a supplement and not commonly associated with severe side effects. However, it is important to always take plenty of water and monitor signs and symptoms of nausea, vomiting, diarrhea or constipation.
As with any supplement, it is important to consult a physician before taking L-cysteine in supplement form.
Article last updated on: March 18th, 2018 by Nootriment