I say “calcium,” you say “strong bones.” I say “vitamin C,” you say “cold prevention.” I say “L-cysteine,” you say “what?” Though unfamiliar to most of us, L-cysteine is a substance our bodies make and use on a daily basis. It is a non-essential amino acid, however, when a person is stressed or physically strained, it becomes increasingly important.

Nevertheless, an interview you are anxious about or stomach bug that just won’t go away are not reasons to start popping L-cysteine supplements. In most cases, it can be adequately synthesized by the body, with most exceptions being individuals affected by metabolic diseases. L-cysteine is like a good friend, you may not think about her every day, but when you need her, she’s there for you.

Just like one has a variety of ways to stay in touch with friends, our body has a variety of pathways to choose from when “keeping us in touch with,” or synthesizing, L-cysteine. According to Livestrong.org, the body can take methionine, an essential amino acid found in our foods, and convert it into L-cysteine. The body’s other option is to take cystine, another compound found in our foods, and turn that directly into L-cysteine. Supplements provide the body with a third method for L-cysteine intake. They contain N-Acetylcysteine, which is in turn converted into L-cysteine.

Now that we know exactly how L-cysteine is made, we are still with the question of why? Well, it turns out there are a variety of purposes for L-cysteine. Often, the body converts the amino acid into glutathione, a powerful antioxidant that can help protect our bodies from free radicals. As described by the National Institutes of Health, “free radicals can be hazardous to the body and damage all major components of cells, including DNA, proteins, and cell membranes.” This damage to DNA is one of the causes of cancer.

If cancer stopping isn’t impressive enough for you, glutathione does much more for the body. According to aminoacidstudies.org, glutathione “inhibits inflammation and leads to an overall strengthening of the immune system.” The antioxidant also stimulates production of leukotriene, which supports macrophages—white blood cells that break down foreign substances in our bodies, such as pathogens, and play a key role in the immune system. Moreover, WebMD states glutathione also helps build and repair body tissues.

Even when not converted into glutathione, L-cysteine is critical to our health. It has detoxification properties, which can help keep dementia and multiple sclerosis at bay since both can be connected to a buildup of toxins that takes place as an individual ages. The amino acid’s cleansing abilities also keep organs healthy and running for longer.

Additionally, L-cysteine helps the body make fatty acids, which are key components of myelin sheaths, the protective coating surrounding nerves like those in the brain and spinal cord. These coverings help prevent environmental damage, and in turn this helps thwart diseases that are associated with the breakdown of the myelin sheaths that cover nerves. Myelin sheaths are also responsible for helping the body send impulses from one end to the other at very high speeds, which is vital to health.

Studies have found that increased levels of L-cysteine can be connected to lower levels of osteoporosis. In addition to these benefits, L-cysteine also has medical uses. Individuals who have acetaminophen poisoning are given treatment that includes L-cysteine.

In order to maintain adequate amounts of L-cysteine in your body, it is essential to eat foods rich with methionine and cystine. People need 1.9 milligrams of L-cysteine per pound of body weight. Dr. Mian Riaz, director of the Food Protein R&D Center at Texas A&M, suggests turning to soybeans, beef, lamb, chicken, fish, sunflowers seeds, oats, cheese, eggs, legumes, and kamut for foods high in cystine. However, it is important to note that cystine is water soluble, so cooking cystine-rich foods in water for too long reduces its concentration.

Sometimes we ingest L-cysteine without even knowing or wanting to; it’s often an ingredient used in packaged bread products (from loaves to buns) as a dough conditioner to produce breads with improved and consistent quality. Whether on an ingredient label or a bottle of supplements, the source of the ingredients is always important. In the case of L-cysteine, Dr. Riaz explains that L-cysteine is “sometimes made from human hair or duck feathers,” which might render it not halal. As for supplements, synthetic supplements that are not made from animal materials are also available. These versions are made from fermenting a nonpathogenic strain of E.coli and are just as easily available as their non-synthetic counterparts. To be sure what you’re consuming is halal, you must always read the labels. If you see “L-cysteine” on the packaging, try to verify it’s from a halal source by contacting the manufacturer, or simply look for the Crescent-M symbol signifying the product is halal. Look for IFANCA halal-certified breads by Kontos Foods in your local grocery store.

Taskeen Khan currently attends UIUC. She has previously written for Huffington Post Teen and Islamic Horizons Magazine. Khan has also won several Silver Keys and honorable mentions in the Scholastic Art and Writing Awards.