I first learned about the Doctrine of Signatures from my dad, Don Tolman. He has spent decades studying ancient wisdom, self-care, and the lost knowledge of natural healing. I remember him talking about how nature leaves clues for us as to how a certain fruit or vegetable might nourish and heal a certain part of our body. This idea fascinated me! It’s called The Doctrine of Signatures. It’s been really cool to have experimented with, and researched this concept. What some people might consider folk lore, science is now backing up. 

Pretty much everything I teach and share is deeply rooted in natural healing, self-care, and ancient wisdom. For example, a huge part of this philosophy aligns with the 7 Principles of Health, fundamentals like air, water, movement, and whole foods. It also aligns with one of the 7 Universal Principles, the Principle of Correspondence. This principle states that patterns in nature reflect patterns within the body: ‘as above, so below; as within, so without”.

What is the Doctrine of Signatures?

The Doctrine of Signatures is the idea that foods and herbs have a built-in “signature” that indicates their medicinal properties. This is a concept that has been recognized for centuries in Indigenous traditions, Ayurveda, Traditional Chinese Medicine, and European herbalism. What’s incredible is that modern science is now confirming many of these connections, proving that nature really does provide the perfect medicine for us. (I provide some examples below).

The origins of the Doctrine of Signatures go way back. Ancient Egyptian and Greek healers like Hippocrates and Galen observed how plants seemed to mimic the organs or conditions they helped heal. Later, Paracelsus (1493–1541), a Swiss physician and alchemist, expanded on this, saying that nature gives us clues about how plants and foods can be used for healing. This is the lineage that I know the Doctrine of Signatures from.

It’s worthy to note that in Traditional Chinese Medicine and Ayurveda, plant shape, color, and taste have long been linked to their therapeutic benefits. Indigenous cultures across the world have also followed this wisdom, understanding that plants have both physical and energetic properties that align with the human body. So there has to be something in it right?!

Nature’s Clues: Foods That Reflect the Body

When I first started studying this, I was blown away by the number of foods that reflect the body parts they nourish. Here’s a few of my favourite examples.

Walnuts and Brain Health

If you crack open a walnut, it looks just like a human brain. Science now confirms that walnuts are packed with omega-3 fatty acids, which are essential for brain function, memory, and reducing inflammation in the brain. Regular walnut consumption has even been linked to a lower risk of Alzheimer’s and other cognitive diseases.

Celery and Bone Strength

If you look at a stalk of celery, it closely resembles human bones. What’s even more fascinating is that bones contain 23% sodium, and celery contains the same percentage of sodium. It’s also rich in silicon, a key mineral for bone strength and density. It’s as if nature designed it specifically to support skeletal health.

Tomatoes and the Heart

One of my favorites is tomatoes. When you slice a tomato, you’ll notice it has four chambers just like the human heart. And guess what? Tomatoes are packed with lycopene, an antioxidant known to protect against heart disease and improve circulation. Modern research from Harvard Health has confirmed that lycopene plays a crucial role in reducing cardiovascular risk, showing once again the power of the Doctrine of Signatures.

Grapes and Red Blood Cells

If you cut open a red or purple grape, it looks a lot like a red blood cell. The same shape, same kind of fluidity. Grapes, especially with the skins and seeds, are packed with resveratrol and other compounds that support healthy circulation. They’re not high in iron, but the vitamin C in them helps the body absorb iron from other foods, which is key for building strong blood. Grape seed extract has also been shown to support capillary strength and microcirculation. There’s been plenty of research showing grape seed extract reduces oxidative stress and protects blood vessels, which backs up what we’ve known all along.

Figs and Reproductive Health

Figs, when split open, look strikingly similar to testicles or ovaries. They are rich in zinc and antioxidants, which are critical for hormonal balance, fertility, and reproductive health. Research shows that figs can increase sperm count, improve motility, and support menstrual cycle regulation.

Avocados and Pregnancy

Then there are avocados, which I think are one of the most incredible examples. If you look at an avocado, it resembles the shape of a pregnant womb. Avocados are packed with folate, a key nutrient for fetal development and preventing birth defects. Even crazier? It takes about nine months for an avocado to grow, just like a human baby!

Kidney Beans and Kidney Function

Kidney beans are maybe one of the most obvious examples, by the name we give them. They are shaped exactly like human kidneys and contain fiber, protein, and minerals that help support kidney function and detoxification. They help maintain healthy blood pressure, reduce kidney stone risk, and support overall renal health.

Sweet Potatoes and the Pancreas

And let’s not forget sweet potatoes, which look like a pancreas. Sweet potatoes are loaded with beta-carotene, which supports insulin regulation and blood sugar balance. They also have a low glycemic index, making them great for people looking to prevent or manage diabetes.

Science Confirms Ancient Wisdom

The more I studied this, the more I realized that science is actually catching up to what ancient cultures already knew. Harvard research has confirmed the benefits of lycopene in tomatoes for heart health. The Journal of Nutrition has linked walnuts to improved brain function. And a 2013 study published in Nutrition Research found that red grapes can reduce oxidative stress and inflammation, which are key factors in cardiovascular disease.These are just a few of the countless examples where modern research is proving that nature’s design is intentional and intelligent.

Want to Learn More?

If you’re curious like me, and are fascinated by health, nutrition and how to nourish your body, (but maybe don’t want to study a nutrition degree), consider my incredible H•E•A•L program.

Often mainstream courses miss out the magic of things like The Doctrine of Signatures and this is one tiny example of what we go through in learning how to empower yourself with your health.