Common Drug-Nutrient & Drug-Herb Interactions

Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Nutrients and the natural compounds found in herbs help your body perform well. However, if you are taking a medication, you need to be aware of potentially dangerous drug and nutrient or drug and herb interactions.


Some things just seem to work nicely when paired together, like fish and chips or toast and butter. But, when it comes to medication, we find that pairings don't always work so well. Some nutrients and herbs interact with medications and alter the way the medicine affects your body. For example, a nutrient or herb might alter the rate at which a drug is broken down or absorbed into your body. These changes can lead to potentially dangerous side-effects. In this lesson, we will take a look at some nutrients and herbs that react poorly when paired with medications.

Vitamin K

I like to think of vitamin K as vitamin Klot because it's a nutrient that helps with blood clotting. You obtain vitamin K naturally from foods like kale and spinach, as well as some green teas. Blood clotting is an important bodily function because when you cut yourself, you want the bleeding to stop.

However, blood clots are not always desirable, particularly blood clots found within blood vessels. If one of these clots breaks loose, it can travel through the bloodstream and cause a stroke. Therefore, people at risk of a stroke or cardiovascular disease will often be prescribed warfarin, which is a blood-thinning medication. As you can imagine, the effectiveness of a blood-thinning drug would be diminished if you ingested a large amount of the blood-clotting vitamin K. For this reason, vitamin K containing foods should be limited when taking warfarin.


Tyramine is a compound formed by the breakdown of tyrosine, which is an amino acid found in many protein-containing foods. Tyramine is obtained from a variety of foods, and it is produced when foods are fermented, cured, aged or when they spoil. Therefore, your body gets tyramine when you eat foods like sauerkraut, hot dogs, aged cheese and even a few favorites, like chocolate.

It's natural to find some tyramine in your body. However, when a high tyramine diet is paired with monoamine oxidase inhibitors (MAOIs), which are drugs used for the treatment of depression, the result can be a dangerous increase in your blood pressure. This reaction happens because MAOIs block an enzyme needed to breakdown excess tyramine, so the compound builds in the body.

St. John's Wort

Wort of St. John (Hypericum perforatum) growing wild
St. Johns wort

Herbs are consumed in many forms. They can be used fresh or dried, added to recipes and teas or capsulated in herbal supplements. People turn to these natural substances as a way to give their diet a healthy boost. However, it's important to note that even though herbs are natural, they contain natural chemical compounds that can interact with the chemical compounds found in drugs.

One popular herb is St. John's wort, which is thought to help with symptoms of depression. Consuming St. John's wort can be a problem when taken with selective serotonin reuptake inhibitors (SSRIs). SSRIs are also drugs that help with symptoms of depression. When this herb and this medication are taken together the effects of the drug are enhanced, which causes high levels of serotonin within the body. When serotonin is elevated it can lead to serotonin syndrome, which is a dangerous condition that causes confusion, agitation, headaches, sweating and changes to heart rate and blood pressure. St. John's wort is thought to interact with a number of different medications, so you should tell your doctor if you are taking the supplement.

Herbs & Blood Thinners

We already discussed the fact that vitamin K has a natural blood-clotting affect that makes it incompatible with blood-thinning medication, like warfarin. It's also important to know that the effectiveness of blood thinners is affected by certain herbs. There are many herbs that can interfere with normal blood clotting and, therefore, should not be taken with blood-thinning drugs.

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