How do Phytonutrients Affect our Health?

Secondary plant substances, also called phytonutrients, are gaining more and more notoriety in the nutrition world! For years, science has put its main focus on primary nutrients, but the results of recent studies reinforce previous theories that plant foods can actually reduce the risk of developing a number of diseases (1).

This is very exciting – phytonutrients have a preventive effect! We want to proclaim these results loudly! So let’s learn more about phytonutrients in this article and look at how they affect our health:

Primary Phytonutrients

Primary phytonutrients serve as nutrients to both plants as well as the human body, and are divided into two groups:

MACRONUTRIENTS – carbohydrates, fats, and proteins – are needed by the body in relatively large quantities, either as energy suppliers or as building blocks for tissues and auxiliary substances like enzymes, hormones, antibodies, etc.

MICRONUTRIENTS – minerals, trace elements, and vitamins – don’t actually provide energy themselves, but make an essential contribution in the metabolism for building macromolecules, for example, or serve as cofactors for enzyme reactions.

Secondary Phytonutrients

“Secondary” indicates that these phytonutrients are not primarily needed for plant growth and development, but serve the plant, for example, as antifoods or attractants.

It’s estimated that secondary phytonutrients are made up of more than 100,000 different substances. About 10,000 of these are currently known and studied, and scientists are gradually beginning to suspect that they have a much broader spectrum of activity than previously thought.

However, researching this spectrum isn’t that easy. All plants and fruits carry very specific combinations of several hundred substances, which are interrelated with each other, and it turns out that isolated substances don’t have the same effect.

Thus, the value seems to lie not in isolating the phytonutrients, but absorbing them by eating the plant as a whole, since the best way for them to develop their health-promoting effects is in natural interaction.

Functions for the Plants

First and foremost, phytonutrients have a fundamental importance to the plant itself. These substances have likely developed as a result of intensive interaction between plants and their environment.

Secondary phytonutrients serve the plant as:

  • Defense substances against predators, for example in the form of bitter substances
  • Protective substances against excessive solar radiation, evaporation, or being infected by fungi
  • Attractants, flavors, scents, and colors to attract pollen-spreading insects and seed-spreading fruit eaters

Examples: Flavonoids give bright colors to fruits, mustard oil glycosides make radishes pungent (which protects them from predators), and carotenoids protect plants from UV rays.

Effects on Humans

Phytonutrients are also incredibly important for us as humans. According to previous research, they have a health-promoting influence on a variety of metabolic processes. In the field of phytotherapy (herbal medicine), phytonutrients have long shown many positive results for humans. The specific preventive and therapeutic effects are eagerly researched by science.

How do phytonutrients affect our health?


  • Metabolism-activating and digestion-promoting ( 2)
  • Blood pressure (3) and cholesterol-lowering (4)
  • Antioxidant (5) and antibiotic (6)
  • Anti-inflammatory (7)
  • Immunomodulatory
  • Anticarcinogenic (8)

Groups of Phytonutrients

Phytonutrients are classified into different groups according to their chemical structure and functional properties:

Alkaloids, essential oils, bitter substances, carotenoids, flavonoids, phytoestrogens, phytosterols, saponins, mucilages, mustard oil glycosides, sulfides, tannins, and others.

Chlorophyll, lectins, and phytic acid can’t be assigned to any of these groups, but still belong to secondary phytonutrients.

Let’s take a closer look at some of the groups:


Alkaloids are those secondary plant substances which primarily serve the plant as natural protection against being consumed; but while they’re toxic to humans in large doses, they can have healing effects in small quantities. To enjoy the health benefits, it’s important to regularly alternate between the different wild herbs.

The best known alkaloids are oxalic acid, nicotine, caffeine, solanine, and theobromine.

Essential Oils

Essential oils are natural aromatic compounds found in seeds, barks, stems, roots, flowers, or leaves and are used by the plant to communicate with its environment. They’re composed of up to 100 different individual substances, with terpenes being the main ingredient. They’re considered to be “non-greasy oils” because they can dissolve into thin air without leaving any residue.

These oils are very valuable to our health. They’re highly bioavailable and can have relaxing, digestive, expectorant, anti-inflammatory, antioxidant, or antibacterial effects on our bodies. Some of the kitchen herbs we’re the most familiar with, like oregano, thyme, and mint, are particularly rich in essential oils.

Bitter Substances

Bitter substances are all chemical compounds that have a bitter taste. We can find them particularly in endive, chicory, and radicchio, among other wild herbs. They increase the secretion of gastric and bile juices and are both appetizing and good for digestion.


Carotenoids are yellow fat-soluble color pigments that are common in plants. They’re mainly found in yellow and red fruits and vegetables, flowers, and leafy greens, and there are currently about 700 known species. Some important subgroups include beta-carotene, astaxanthin, lutein and zeaxanthin.

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Flavonoids are a group of phytonutrients that include a large proportion of plant pigments: Anthocyanins, for example, provide a variety of colors ranging from orange to red to blue. The best example of this is wild blueberries. Anthocyanins are said to have particularly antioxidant, anticarcinogenic, and antibiotic properties.

Mustard Oil Glycosides

Plants belonging to the cruciferous family like mustard, cress, horseradish, as well as cabbage vegetables, contain mustard oil glycosides, also known as glucosinolates. This is a substance that contains sulfur and that, when combined with oxygen as it’s being chewed, converts into sulforaphane. Glucosinolates are responsible for their typical pungent taste and have warming, metabolism-activating, and disinfectant effects, in addition to being strong antioxidants and anticarcinogens.


Tannins are plant substances found in blackberry leaves and ground ivy, among other sources. Their special property is to bind skin proteins and mucous membranes and transform them into insoluble compounds. As a result, they are astringent and anti-inflammatory, and also heal wounds, protect the mucosa, and regulate diarrhea.

Which Foods Are Rich in Phytonutrients?

As the name suggests, phytonutrients are found exclusively in plants. The main sources are vegetables, fruits, legumes, seeds and nuts, and especially wild herbs.

To ensure that you get enough phytonutrients in your diet, the German Nutrition Society (GNS) recommends eating five portions of fruit and vegetables per day.

In light of this recommendation, you might realize that by consuming five servings of vegetables and fruits, this puts you right in the midst of a raw vegan diet!

Unfortunately, the reality of today’s eating habits, in conjunction with the excess of convenience products and inexpensive meat products in our supermarkets, deviates far from the official recommendations of the GNS. It’s very apparent at this point that we need some clarification!

So here’s our recommendation for nutrition rich in vegetables:

  • Look for a diet rich in flavors, fragrances, and colors, and prioritize color-intensive and bitter plants and fruits that contain seeds.
  • Choose organically grown foods – studies show that organic foods contain more phytonutrients than conventionally grown foods (10).
  • Consume nature’s offerings as a whole in order to reap the benefits of the interaction of all the ingredients. Taking concentrated preparations (supplements) doesn’t make any sense from a scientific point of view.

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Ulrike Eder (Author)

Ulrike is a naturopath, Holistic Nutrition Coach, Hippocrates Lifestyle Medicine Coach and phytotherapist. Together with her husband, Jürgen, she leads the Holistic Nutrition Coach training program of Your Nutrition Academy.



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