10 Mar 2021

Medicine in the garden

From Afternoons, 3:08 pm on 10 March 2021

Immunologist Catherine Whitlock spent months researching 100 plants with a history of medical use. 

She shares the best of the bunch in her book,  Botanicum Medicinale: A Modern Herbal of Medicinal Plants.

Dr Whitlock told Jesse Mulligan she found it fascinating how many plants out there provided us with medicine.

She says attitudes towards herbalism are changing, and there is a place for both – the pharmaceutical approach of extracting vital compounds from plants as well as the holistic approach.

“The medical profession has been very evidence-based in recent years and there’s a real kind of eye-opening approach now that there is a whole lot out [of plants] there that we should be investigating.

“The plants we chose [in the book] highlight the depth and breadth of the plant kingdom and what they can do for us.

“We were trying to cover supplements, and we were trying to cover food sources as well as the pharmaceutical drugs that are derived from these plants so the book kind of marries a botanical approach.”

Is there evidence?

She acknowledges pharmaceutical drugs often have more research backing them, while herbal medicine’s evidence is often anecdotal.

“But it is encouraging, there’s a lot more research in this area now and because of my scientific background I was able to delve into what data there is there.

“The other thing we use quite a lot is this meta analysis where you take a large number of studies and you use statistical methods to pull them together, so if the studies are small that helps to correct for that, and I was able to reassure myself that what we were putting in was scientifically valid.”

Historically, ancient herbalists used traditional forms of medicine as prevention to diseases rather than cure. Dr Whitlock says that’s generally still the case.

“Historically we are hunter-gatherers and we would have had the opportunity to gather large numbers of different plant species and of course there were no clinical trials those days – it was often a fairly drastic way of testing out new plants, people often died, but every so often there was a certain finding and a new plant would reveal its new medicinal uses.”

'You have to understand what you’re doing'

Dr Whitlock has a word of caution about buying over the counter supplements. She says she’s not medically trained as a herbalist but urges people to see their GP and a qualified naturopath if they consider taking herbal supplements.

“It’s very difficult to get the right quantities of active compounds in those – you have to understand what you’re doing and it definitely is worth consulting a medical herbalist about that but in terms of diet … I’m quite a big fan of herbal teas.

“Every time I look at the herbal tea packet and see cardamom or liquorice or peppermint – they’re all plants being featured in this book, and you wonder how much active compounds you’re getting every time you drink that cup of herbal tea.

“So I look at the quantities and I think it’s got x number of micrograms of valerian root in it – what does that mean, am I getting something that will help me sleep?’

“These are potentially very active compounds in these plants and you have to be careful, if you’re taking prescription medications, you really need to let your doctor know if you’re considering taking herbal supplement as well.

“The other thing that’s very relevant here in herbal medicine preparation is they often rely on synergistic effects so it’s the product of individual compounds working together that create that effect.”

Dr Whitlock says doses are crucial too, hence why it’s important to seek specialist help.

“They often say that toxicology is only small step away from pharmacology – it’s very easy to take an overdose of all sorts of drugs and the same applies to plant-based materials.

“These are powerful compounds we need to have respect for them and understand that it can have quite profound effects.”

What are some uses for plants?

Still, a high proportion of pharmaceuticals use plant compounds, Dr Whitlock says, with those in the fields of pain control, cancer and cardiology benefiting.

“But increasingly with the kind of technology where you can screen large numbers of compounds and large numbers of plants, they’re thinking that we’re heading down the route of finding cures for Alzheimer’s and all kinds of other awful diseases we encounter nowadays.”

In plants, there are three key compounds - flavonoids, glycosides, Alkaloids, she says. They had largely been brushed aside until the 1970s, because they were merely seen as by-products of plants’ metabolism.

“But now it’s understood that actually they are the defense mechanisms for plants. So plants can’t run away, they can’t fight off microbes and bacteria and viruses like the sophisticated system of humans can so this is what they’re there for in plants, and in many ways some of the ways that they work are replicated in the ways we use them – so the flavonoids are antioxidants, so this is where the preventative medicine comes in.”

For example, she says it may potentially be used in cancer treatments as the toxicity in which it fights off dangers to protect the plant could be used to fight against cancer cells.

“Their toxicity extends to their toxicity against cancer cells. It’s all about harvesting … the properties of these different compounds in plants and using them for medical use.

“Antioxidants work by mopping up free radicals which are by-products of metabolism and often very damaging – so that’s one part of their story of their relationship with cancer.

“Cancer treatment nowadays involves a lot of toxic drugs and some of those toxic drugs come from secondary metabolites – many of them actually there’s a list of five or six we feature in the book.”

Flavonoids can be easily identifiable in plants, she says, because they provide the colour. For example, the orange colour in carrots.

“That’s one of the reasons why when you’re thinking of a dietary source of preventative medicine if you like, they always talk about the rainbow diet. The more colour you have in your diet, the more flavonoids and antioxidants and anti-flammatories you’re taking in.”

There’s a few other quirks that stick out from the book for Dr Whitlock. One is that garlic’s most active compound – the antibacterial allicin – is destroyed in the cooking process.

She says that’s why it features heavily as processed raw in Mediterranean foods – which has been under examination for longevity.

Another one is lavender –  which is associated with being a sleep aid. Dr Whitlock says it’s now understood it’s better to inhale the smell through your nose rather than mouth because the feelings of relaxation and potential sleepiness are only triggered by the smell receptors in the nose – they’re triggered much less efficiently if you breathe through your mouth.

Sage is also believed to help with the hot flushes people experience with menopause. Dr Whitlock says she looked hard for the evidence but couldn’t quite understand how it worked.

“Hot flushes are essentially a dysregulation in the temperature mechanism in the brain and they think somehow a compound in sage is targeting that. I think the mechanisms aren’t well understood but it’s definitely out there, several of the plants are big in the menopause world and that’s one of them.”