Is taking a stack of supplements at the same time smart or actually dangerous?

Taking a stack of supplements can be risky, and the greatest danger lies not in the supplements themselves but in combinations with prescription medications. Almost a quarter of American adults combine prescription drugs with dietary supplements, yet most people do not mention this to their doctor. That makes identifying problems difficult, because the doctor and pharmacist simply do not know what someone is taking additionally at home¹.

Not all supplements carry the same risk when combined with medications. Two herbal supplements stand out clearly in a negative way: St. John's wort and goldenseal demonstrably cause clinically relevant interactions with prescription drugs. Anyone taking medications should avoid these two. A middle group, including curcumin, echinacea, garlic, green tea extract, and kava kava, can cause problems with certain medications, but the evidence for this comes largely from laboratory research and has not always been confirmed in humans. A third group, including black cohosh, cranberry, ginkgo, milk thistle, American ginseng, saw palmetto, and valerian, has a low likelihood of interactions and is probably safe for most people to combine with common medications, though caution is always appropriate¹.

There are also supplement combinations that are genuinely worthwhile. When a child is taking a course of antibiotics, giving probiotics simultaneously at a high dose (at least 5 billion live bacteria per day) can substantially lower the risk of diarrhoea: from 23% to 8%. On average, six children need to be treated to prevent one case of diarrhoea. Across 24 randomised studies involving more than 4,400 children, no serious adverse effects were attributed to probiotics, although there is one exception: in severely ill or immunocompromised children, serious adverse effects have been reported outside these studies, so caution is warranted in that group².

For people who want to support muscle function later in life, there are preliminary indications from small studies in older adults that certain supplements targeting the energy metabolism of muscle cells may help. These include MitoQ, urolithin A, omega-3 fatty acids, and the combination of glycine plus N-acetylcysteine (GlyNAC). The quality of evidence is limited, however, and safety and long-term effectiveness have not yet been sufficiently studied. Furthermore, several authors of the review article on which this is based receive funding from manufacturers of these supplements, which puts the results in a different light³. NAD precursors such as NMN or NR are often promoted as muscle-supporting, but the same research shows that any effects on physical functioning are not linked to improvements in the mitochondrial function of muscles. The assumed mechanism of action therefore does not hold up, making the value of these products for this purpose unclear³.

The practical conclusion has two parts. First: anyone taking prescription medications should always inform their treating doctor or pharmacist about which supplements they are also using. St. John's wort and goldenseal are the most risky when combined with medications and deserve explicit attention. Second: taking a broad stack of supplements without a specific reason offers no proven benefit for most healthy adults, while the risk of interactions with medications is real. Targeted use, based on a concrete complaint or deficiency, has more supporting evidence than preventively swallowing dozens of pills at once.