There’s limited evidence on how combinations of drugs interact, or how diet and nutrition influence their effects. A study on the effects of combinations of psychiatric drugs and a common dietary supplement had surprising results – results that show just how poorly understood and under-researched this area is.
Researchers have found that combining drug therapies has long-term benefits, for instance, in treating depression in patients with bipolar disorder. However, taking a folic acid supplement might interfere with the drugs’ therapeutic effect.
Although treatment of mental health disorders with multiple drugs is the norm, there’s not much evidence about which combinations help to keep patients well in the long-term, and how these may be affected by diet and nutritional supplements.
The study had addressed these problems by investigating whether a combination of commonly-used drugs really is better than using a single drug. The researchers have also examined whether the action of these drugs is influenced by a vitamin supplement.
We showed that patients given a combination of drugs commonly used for treating bipolar disorder (quetiapine and lamotrigine) had fewer symptoms of depression and were less likely to relapse, compared with those given quetiapine alone. These findings make sense, since quetiapine is relatively quick-acting, while lamotrigine takes longer to reach its full effect.
It is notable that the effect of folic acid in our study was the opposite of what was predicted – it made patients’ symptoms worse. This surprising result raises the possibility that there are many other foods and supplements that may influence the effects of prescribed drugs.
Effects of this type are rarely, if ever, captured by drug trials. But they could prevent prescribed drugs from working as intended, or result in additional side effects. To add a further level of complexity, it seems likely that genes could also affect these relationships. For example, there are a number of genetic variants that influence the actions of folic acid. These genetic variants could, feasibly, influence the action of some drugs. We will examine some of these possibilities in our data set, as an additional study.
We tend to think of vitamins and dietary supplements as natural, so we assume that their effects are beneficial. However, as with prescribed drugs, the nutrients and supplements we take are ultimately just chemicals and can have profound effects on our bodies, both positive and negative.
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