The Inner Life of Plants

A plant can't run from danger, chase its food or seek shade on a hot day. Rooted to one spot, it has done something remarkable instead: it has become a master chemist. And many of the compounds it makes to protect itself turn out to help us too.

Nature's laboratory

Every plant makes the basic building blocks it needs to grow. But alongside these, plants make an extraordinary range of extra compounds, known as secondary metabolites. They act as sunscreen against strong light, armour against insects and fungi, scent to attract pollinators and signals to warn their neighbours. Scientists have identified more than 200,000 of them so far, and many more are still waiting to be discovered.

These are the compounds behind the warmth of ginger, the colour of beetroot, the bite of garlic and the calm of chamomile. They are also where much of modern medicine began. Aspirin was developed from a compound found in willow bark, and the heart medicine digoxin still comes from the foxglove.

More than the sum of its parts

Modern medicine usually works by finding the single "active ingredient" in a plant, purifying it and giving it in a measured dose. That approach has saved countless lives. But it can also leave something behind, because in nature compounds rarely work alone.

Scientists call this synergy: when compounds working together achieve more than any of them could alone.¹ In a living plant, one compound may help another get into the body, protect it from being broken down, or attack a problem from a different direction at the same time.

A plant is not one medicine. It is a whole team of compounds, each with its own part to play.

Synergy in action

Familiar herbs in a new light

Rosemary: a self-renewing shield. Rosemary's main protective compound, carnosic acid, works in an unusual way. When it meets damaging free radicals, it is changed into carnosol, which goes on protecting, and then into further compounds that carry on the work, like a relay team passing on the baton. Carnosic acid also switches on the body's own defence system, a master switch called Nrf2 that turns on hundreds of protective genes, and has been shown to protect nerve cells in laboratory studies.² Meanwhile, rosemary's aroma brings its own gifts. In one study, the more 1,8-cineole from rosemary oil people absorbed simply by breathing the scented air, the better they performed on tests of speed and accuracy.³ Alongside these sit rosmarinic acid, a calming anti-inflammatory, and many more. No wonder rosemary has been the "herb of remembrance" since ancient Greece. (For rosemary's role in the long-lived village of Acciaroli, read A Natural Age.) (See The Quiet Fire.)

Rosemary's protective power even works in the frying pan. In one study, marinating steaks in a marinade containing rosemary before grilling cut the cancer-linked compounds called heterocyclic amines, which form when meat is cooked at high temperatures, by up to 88%.⁴

Ginger: one root, many medicines. Fresh ginger is rich in gingerols, which give it its fresh, zingy heat. When ginger is dried or cooked, some gingerols turn into shogaols, which are more pungent and, in laboratory studies, often more strongly anti-inflammatory.⁵ Heat also creates zingerone, with its sweeter, mellower warmth. Herbalists have long used fresh and dried ginger differently: fresh to warm the surface and ease a cold, dried to warm the digestion more deeply. Chemistry now helps explain why.

Turmeric and black pepper. Curcumin, the golden compound in turmeric, is poorly absorbed on its own. When people took it with piperine from black pepper, the amount reaching their blood rose by around 2,000%.⁶ Traditional cooks in India have been pairing the two for centuries.

Garlic's clever chemistry. A whole garlic clove contains very little allicin, its most famous compound. Allicin only forms when the clove is crushed or chopped, mixing two ingredients that the plant keeps in separate compartments until it is damaged.

Adaptogens: herbs that help us adapt

Adaptogens are herbs that help the body adapt to stress, whether physical, mental or emotional, and return to balance. They don't push the body in one direction like a stimulant or a sedative. Instead, they seem to help it respond more flexibly, acting on the stress hormone system and on many of the body's networks at once.⁷ (See The Cortisol Clock.) This many-sided, balancing action is exactly what we'd expect from a team of compounds rather than a single one.

It's no coincidence that many of the most prized adaptogens grow in tough places: rhodiola on cold, windswept Arctic and mountain slopes, ashwagandha in the hot, dry soils of India and the Middle East. A plant that can't escape drought, frost, fierce sun or hungry insects must defend itself chemically, and under pressure it makes more of its protective compounds. Scientists have suggested that when we eat these stress-hardened plants, their defences may in turn help strengthen ours, an idea known as xenohormesis.⁸ In a sense, the plant's hard-won resilience is passed on to us. (Read more in Stressed Plants, Stronger Medicine.)

Ashwagandha: the whole root. Ashwagandha (Withania somnifera), a treasured herb of Ayurveda, contains a family of compounds called withanolides, along with alkaloids and other constituents, which together are thought to give the root its calming, strengthening action. In a trial using a full-spectrum extract of the root, people under stress who took it for two months had lower stress and anxiety scores and around 28% lower levels of the stress hormone cortisol than those taking a placebo.⁹

Rhodiola: a team effort. Rhodiola (Rhodiola rosea), or golden root, grows in the cold mountains of Scandinavia, Siberia and the Arctic, and was used by Vikings and Russian soldiers for strength and endurance. Its best-known compounds are salidroside and a group called the rosavins. In animal studies, the whole extract was more active against stress than its best-known compounds given on their own, or even mixed together, suggesting that other, less famous constituents play an important part.¹⁰

Reishi: two families of medicine in one mushroom. Reishi (Ganoderma lucidum), known in China as lingzhi and revered for more than 2,000 years as the "mushroom of immortality", is one of the most prized adaptogens in traditional medicine. Its gifts come from two very different families of compounds working side by side. The beta-glucans, complex sugars in the mushroom's cell walls, help to train and balance the immune system. The triterpenes, more than 100 bitter compounds called ganoderic acids, have been studied for calming, liver-protecting and anti-inflammatory effects.¹¹ The two dissolve differently: beta-glucans in hot water, triterpenes in alcohol. That is why traditional reishi is simmered for hours as a decoction, and why good-quality modern extracts often use both water and alcohol, a "dual extraction", to capture the whole mushroom. (See The Hidden Kingdom.)

Ginseng: compounds in balance. Asian ginseng (Panax ginseng) contains more than 100 different ginsenosides. Remarkably, some of them have opposite effects: one of the main ginsenosides, Rg1, tends to be stimulating, while another, Rb1, tends to be calming. Rg1 encourages new blood vessels to grow, for example, while Rb1 restrains them.¹² In the whole root, these opposing forces are held in balance, which may help explain ginseng's reputation for restoring energy without overstimulating.

Adaptogens are powerful herbs, and they aren't right for everyone. Ashwagandha, for instance, is warming and can affect the thyroid, ginseng can be too stimulating for some people, and both ginseng and reishi interact with several medicines, including blood thinners. The right adaptogen depends on your constitution and your whole picture, so it's best to seek a practitioner's guidance rather than self-prescribe. (See The Architecture of Balance and When Plants Meet Pills.)

Lessons for modern medicine

The plant that guards its own medicine. Barberry contains berberine, a compound that attacks bacteria. On its own, bacteria can defend themselves by pumping berberine straight back out. But scientists discovered that barberry also makes a second compound, which blocks that pump. Together, the two are far more powerful than berberine alone.¹³

The wormwood that fights malaria. Sweet wormwood (Artemisia annua) gave the world artemisinin, one of the most important malaria medicines, and a Nobel Prize in 2015. Yet in studies in mice, the dried whole plant cleared malaria parasites more effectively than the purified drug, and even worked against parasites that had become resistant to it.¹⁴ Other compounds in the leaf appear to help.

Ancient wisdom, modern science

Traditional herbal medicine has always worked with whole plants and with combinations of herbs. Chinese herbal formulas often include liquorice as a "harmoniser" to bring the other herbs together, and Western herbalists have long combined herbs to support and balance one another.

Modern research is now beginning to explain what herbalists observed for generations: that a plant, or a blend of plants, can act on several of the body's systems at once, often more gently than a single strong compound. This is one reason whole foods and herbs can be so nourishing, and why their effects can be hard to capture in a capsule.

Bringing synergy into your kitchen

• Pair turmeric with black pepper and a little fat, such as olive oil or coconut milk, to help your body absorb it.
• Crush or chop garlic and wait about 10 minutes before cooking, so its allicin has time to form.
• Marinate with rosemary. Add rosemary, garlic and olive oil to meat or fish before grilling or roasting.
• Use ginger both ways: fresh in teas and stir-fries, and dried in warming soups, stews and baking.
• Cook tomatoes with olive oil. Their red pigment, lycopene, is absorbed better when cooked and eaten with fat.
• Add lemon to green tea. In laboratory tests that copy digestion, citrus juice helped protect green tea's beneficial compounds.¹⁵
• Use fresh herbs generously. A handful of parsley, coriander or basil adds a whole spectrum of plant compounds to a meal.
• Choose whole herbs and teas from trusted, good-quality sources, where the plant's natural balance is kept.

At Rootwise, herbs are chosen for the whole person, not just a single symptom, and combined with food and lifestyle so that each part of your plan supports the others.