Many people assume that because a natural health product is “natural” then it is most likely safe. While the vast majority of supplements are extremely safe, the potential for interactions with prescription medications is always present. In most cases, a qualified health care practitioner can predict these interactions. In other situations where an interaction was not expected, the practitioner can at least manage medications and supplements accordingly, but only if he or she has all of the available information.

Although many interactions are quite minor, there are too many possibilities of major interactions that you should never take the risk of not telling your doctor. As you’ll see in some of the given examples, even common herbal teas can interact with your pharmaceutical drug prescriptions.

There are a number of circumstances that can lead to an interaction. Here are a few of the most common scenarios:

1. A supplement increases the metabolism of a drug: Any drug, supplement or nutrient that goes into our bodies has to first, be absorbed by our digestive tract and second, go through our liver. Our liver’s job is to metabolize (break down) unknown molecules and prepare them to be excreted from the body. The liver relies on various enzymes to carry out this process and the most common enzyme that many drugs pass through is a group called Cytochrome P450. Doctors rely on the fact that this enzyme activity is stable and consistent. So, if something were to inadvertently increase the activity of Cytochrome P450, any drug entering the body would be broken down more quickly and, therefore, become less active or useful. This is very bad if your body desperately needs the help that the pharmaceutical drug is providing.

The classic example in this scenario is St. John’s Wort (Hypericum perforatum), an herb commonly used to treat mild depression. St. John’s Wort is a red flag for most doctors because of its ability to up-regulate these liver enzymes and alter drug concentrations in the body. While St. John’s Wort is the classic example, it should be noted that there are many other agents that can induce Cytochrome P450 and perhaps many natural health products that we don’t even know have this ability.

2. A supplement decreases the metabolism of a drug: Just as some supplements can up-regulate the activity of Cytochrome P450, there are other natural health products that can down-regulate the enzyme activity. Although not truly a supplement or product, the classic example fitting in this category is grapefruit. Ever had your doctor tell you that you’re supposed to avoid grapefruit juice? This is why. If you were to suddenly go from drinking no grapefruit juice to drinking a full glass every day, your medications will work too well! This can be equally dangerous to your health (once again, depending what medication you’re on).

3. A supplement directly increases the effect of a medication: From a basic view, this is very straightforward – a drug and a natural health product both have the same effect on the body. If we consider the pharmaceutical class of selective serotonin reuptake inhibitor drugs (SSRI’s) and the natural health supplement 5-hydroxytryptophan (5-HTP), both are commonly used for treating anxiety and depression. Moreover, both are acting to increase serotonin levels in the brain. SSRI’s prevent the breakdown of serotonin, while 5-HTP increases the production of serotonin, but both have the same end result: more serotonin.

Another example perhaps better illustrates how this effect can be more inconspicuous. Ashwaganda is an herb commonly used as a rejuvenating tonic to manage stress, improve immune function and even decrease inflammation. However, not many people know that ashwaganda also increases thyroid function by increasing the conversion of thyroid hormones, T3 to T4. In some cases, this thyroid effect can be considered a secondary consequence of Ashwaganda. Therefore, for individuals that are considered hypothyroid (low functioning thyroid) and medicated with Synthroid (a medication used to up-regulate the production of thyroid hormone), they can end up in an over active thyroid state if they use the herbal supplement. This over-correction can be quite severe and even deadly if not properly managed.

4. A supplement directly opposes the effect of a medication: Using our same hypothyroid patient as an example, other health products such as lemon balm (Melissa officinalis) can actually block the conversion of T3 to T4. This obviously creates the opposite problem and makes the Synthroid drug less effective, keeping the patient in a low functioning thyroid state.

As an additional example, given the large proportion of the population on blood pressure lowering medications, there are many health products that have the potential to oppose these drugs. Licorice root (Glycyrrhiza glabra), an herb also used to help the body deal with stress, is very well known to retain sodium in the body and, thereby, raise blood pressure. If you’re drinking licorice tea everyday and wondering why your blood pressure medication “isn’t working”, this is a good place to start looking.

It goes without saying but a drug or medication can also be viewed as negatively impacting or benefiting the action of a natural health product (as opposed to the natural supplement always acting upon the medication). The reason for the chosen scenario is that drugs, when altered even slightly, have a greater potential for toxicity or side effects. In other words, pharmaceutical drugs have a much narrower therapeutic window, so even slight alterations in dosage can have vast effects.

With all of these potential interactions in mind, it’s quite clear that your doctor needs to know exactly what medications and natural health products you are consuming on a regular basis.

“Okay, but if it’s really a benign supplement like a probiotic or B-vitamin complex then it’s not necessary to tell your healthcare practitioner, right?” 

Sorry to say that you’re wrong – ALL supplements must be disclosed. Even something as seemingly harmless as a probiotic or B-vitamin complex can theoretically aggravate your condition or interact with your medications. Probiotics alter your gut microflora and can modulate your immune function, theoretically aggravating an auto-immune condition (or decreasing the effectiveness of immunosuppressive drugs). B-vitamins are crucial for neurological function and liver pathways, so neurotransmitters may be altered and detoxification pathways may be improved – even though these are generally benefits of supplementation, they can have negative effects if done too quickly or without your doctor’s knowledge.

The bottom line is that even if you don’t think it’s important for your doctor to know about your natural health product consumption, your doctor sure wants to know. So do yourself and your physician a favor and keep the lines of communication open.