Everything You Should Know About Magnesium Stearate

Medically reviewed by Debra Rose Wilson, PhD, MSN, RN, IBCLC, AHN-BC, CHT on August 25, 2017Written by Kelli Hansen, RN, CMCN, CSA, CDP on August 25, 2017

What is magnesium stearate?

Have you ever wondered what that coating on your medications and vitamins is? It’s an additive made from magnesium stearate.

Magnesium stearate is a fine white power that sticks to your skin and is greasy to the touch. It’s a simple salt made up of two substances, a saturated fat called stearic acid and the mineral magnesium. Stearic acid can also be found in many foods, such as:

  • chicken
  • eggs
  • cheese
  • chocolate
  • walnuts
  • salmon
  • cotton seed oil
  • palm oil
  • coconut oil

Magnesium stearate is commonly added to many foods, pharmaceuticals, and cosmetics. In medications and vitamins, its primary purpose is to act as a lubricant.

What does magnesium stearate do?

Magnesium stearate is an additive that’s primarily used in medication capsules. It’s considered a “flow agent.” It prevents the individual ingredients in a capsule from sticking to each other and the machine that creates the capsules.

It helps improve the consistency and quality control of medication capsules. It’s possible to create medication capsules without magnesium stearate, but it’s more difficult to guarantee the consistency and quality of those capsules. Magnesium stearate is used to delay breakdown and absorption of medications, so they’re absorbed in the correct area of the bowel.

What are the health risks of magnesium stearate?

Magnesium stearate is generally recognized as safe to consume. If you ingest too much, it can have a laxative effect. It can irritate the mucosal lining of your bowels. This causes your bowels to spasm, triggering a bowel movement.

Some people on the internet claim that magnesium stearate suppresses your immune T-cell function and causes the cell membrane integrity in your helper T-cells to collapse. However, there’s no scientific evidence to support those claims.

These claims have been made based on a single mouse study that was related to stearic acid, not magnesium stearate. Mice lack an enzyme in their T-cells that humans have. This makes stearic acid safe for us to ingest.

Some people have also claimed that magnesium stearate might interfere with your body’s ability to absorb the contents of medication capsules. But again, there’s no scientific evidence to support those claims.

It’s possible to be allergic to magnesium stearate, however, and it can be difficult to avoid this food additive.

How much is safe to consume?

The U.S. Food and Drug Administration (FDA) has approved magnesium stearate for use as an additive in food and supplements. According to the National Center for Biotechnology Information, it’s considered safe for consumption at amounts below 2,500 milligrams (mg) per kilogram per day. For a 150-pound adult, that equals 170,000 mg per day.

Capsule and medication manufacturers typically only use small amounts of magnesium stearate in their products. When you take their products at the recommended dose, they don’t contain enough magnesium stearate to cause negative side effects.

Key tips

Don’t take everything you read on the internet as truth. If you have concerns about an additive or supplement that you’re thinking about taking, do your research first. If there are no research studies to back up claims made online, they’re likely false. If in doubt, talk to your doctor.

Always consult your doctor before trying a new supplement or medication. Although magnesium stearate isn’t one of them, some products and ingredients can impact how your body absorbs drugs. Your doctor can help you learn about the potential benefits and risks of adding a new supplement or medication to your routine.

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