The science behind herbal supplements: is ‘natural’ always better?

By The Gut Health Doctor Team

Dr Megan Rossi in a lab looking through a microscope

Herbal supplements have boomed in popularity in recent years, after being used for thousands of years across many cultures. In fact it’s estimated that as high as 4 billion people worldwide take some form of herbal medicinal products, with the market worth over $6 billion.


But, while a few show benefits, others just aren’t supported by the evidence – and could even be damaging. So, it’s important to be careful.


Here’s the latest science on herbal supplements


A herbal medicine or supplement is essentially the active ingredient of a herb at a highly concentrated level. Just like conventional medicine, herbal products also have an effect on the body. It’s also important to remember that some medications were in fact originally derived from plant or natural compounds, including morphine, aspirin and the first antibiotic – penicillin (a type of fungi).


When it comes to certain gut health complaints, there are some herbal supplements that may be worth knowing about.


  • Peppermint for bloating. There is evidence that peppermint oil capsules can help with bloating and abdominal pain in IBS triggered by trapped gas, because they act as an antispasmodic, which means they relax your gut muscles and suppress muscle spasms. Peppermint is also a top source of polyphenols (beneficial plant chemicals).
  • Ginger for nausea. Ginger can act as a natural antiemetic (anti-nausea medication), which can be especially useful in early pregnancy. Drinking ginger tea instead of citrus fruits may also help with heartburn and acid reflux. There are, however, some cases where this shouldn’t be taken, so check with your healthcare team first. 
  • Curcumin for IBD, found in turmeric. There is growing evidence that taking in capsule form (studies used 1.5-4g per day) may help with the management of the inflammatory bowel condition Ulcerative Colitis (when taken alongside prescribed medication e.g. mesalazine). Always speak to your consultant before taking supplements.


However, just because something comes from a natural source doesn’t mean it’s benign and doesn’t guarantee its safety. If not used correctly, some herbal supplements could have potentially harmful results. Plants can create powerful toxins, which can be fatal to humans if ingested in high enough doses. Two examples of ‘natural’ compounds derived from plants that we know can be dangerous are morphine and cyanide.


  • Morphine. The powerful opioid drug used for pain relief originates from the humble opium poppy plant. It’s highly addictive, can cause euphoria (think heroin) and overdosing could be fatal
  • Cyanide. The poison made famous by many a murder mystery is released from compounds found naturally in some plants, such as the stone of bitter apricots. That’s why EFSA (the European Food Safety Authority) guidelines advise against eating the stone (along with common sense). But don’t worry – the chemical is contained within the stone so it doesn’t affect the flesh of the fruit at all.


Potential risks of herbal supplements


  • Lack of testing. Unlike pharmaceuticals that are tested extensively to assess efficacy and safety, herbal supplements can be sold without this evidence or safety evaluation, and marketed with claims that aren’t backed by the science. In fact, kidney failure resulting from contaminated herbal concoctions was sadly something I saw quite often when I worked on the Kidney ward.
  • Drug interactions. If you’re taking other medicines, herbal supplements may reduce or increase the effects. An example of this is the herbal supplement St John’s wort, which interferes with a key enzyme of drug metabolism. This can interfere with medications including warfarin, the oral contraceptive and immunosuppressants. 
  • Body function. High doses of certain supplements, including green tea and multi-supplements marketed for weight loss, have been shown to contribute to liver inflammation, which can affect the body’s detoxification and lead to more serious health consequences.


Herbal supplements and your GM (gut microbiota)


There have been some test-tube studies showing that certain herbs have antimicrobial action, meaning they fight against ‘harmful’ organisms in the gut. But it’s important to be aware they’re not selective, so they can also kill other health-promoting bacteria that aren’t the target.


There are no high-quality trials in humans to date either. What’s more, these herbal antimicrobial products are poorly regulated and can vary significantly in dose and formulation, meaning that some may in fact do more harm than good. 


Key take home


Ultimately, I’m a big fan of all herbs and spices in their original form. They not only add amazing flavour, but also count towards your diversity goals as part of your 30 different plant points per week (think ¼ point for each). Next time you’re doing your food shop, pick up a herb or spice you’ve never used before and get experimenting in the kitchen this week. Diversity is the spice of life.



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