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Secondary plant metabolites — also known as phytonutrients

Reading Time: 2 minutes

What are phytonutrients?

Secondary plant substances are also referred to as phytonutrients, phytochemicals or secondary plant ingredients. But how do the substances work? Secondary plant metabolites are responsible for dyes, bitter substances, fragrances and flavours in food. Phytonutrients do not belong to the essential nutrients of the body, but are involved in a variety of metabolic processes. Neurological, anti-inflammatory and antibacterial effects are also attributed to them.1

Those who eat healthy and varied mixed foods consume about 1.5 g of secondary plant metabolites via food every day. Because vegetarians usually only eat plant-based foods, they usually consume an even larger amount of secondary plant metabolites.1

How many secondary plant metabolites are there?

According to current knowledge, there are about 100,000 secondary plant metabolites, of which about 5,000 to 10,000 occur in our food.1 We have listed the nine main groups of secondary plant metabolites:

  • Carotenoids
  • Flavonoids
  • Monoterpenes
  • Glucosinolates
  • Phenolic acids
  • Phytosterols
  • Phytoestrogens
  • Sulphides
  • Saponins

What are the functions of secondary plant metabolites?                                                 

Phytonutrients give vegetable foods their colour, their scent and their aroma. The effect of secondary plant metabolites in terms of dyes, bitter substances, fragrances and flavourings is clearly illustrated by examples:2

  • Yellow peppers, orange pumpkins and red tomatoes get their colour via carotenoids.
  • Saponins provide the bitter substances in pulses.
  • Monoterpenes give herbs their fresh scent.

If you eat a balanced diet and rely on a mixture of fruits, vegetables, potatoes, legumes and nuts, you can ensure an adequate intake of secondary plant metabolites. A diet as colourful as possible can help in making the right choice for healthy eating.

Which foods contain secondary plant metabolites?

Secondary plant metabolites seem to be easily available — but where exactly can you find them? Incorporating phytonutrients into your daily diet is easier than you might think. If you value eating well and already enjoy a variety of colours of fruits and vegetables, you won’t need to make any big changes.

If you want to use these metabolites to support your future health, you can follow this selection of examples showing where secondary plant metabolites are obtainable: Perhaps you will find inspiration for new nutritious cooking ideas. Dig in when fruits, vegetables, nuts and legumes are offered. The more colourful, the better — variety in a healthy diet is key, and this can be achieved with many different types of foods.

Secondary plant metaboliteOccurrence in food
Carotenoids, for example Lycopene Beta-carotinoidTomatoes, watermelon, red grapefruit Apricots, pumpkin, spinach, kale, broccoli3
Flavonoids, e.g. Anthocyanins Flavonols QuercetinAubergines, cassis, blueberries, blackberries Apples, peppers, celery, carrots, grapefruit, oranges, onions Onions, kale, leeks, tomatoes, berries4
MonoterpenesLemons and oranges (zest and juice), caraway, ginger, grapes, apricots, mint, celery leaves, spices5
GlucosinolatesCabbage including Brussels sprouts, cauliflower, kale and white cabbage, broccoli, horseradish, radishes, cress, mustard6
Phenolic acidsKale, white cabbage, green beans, spinach, lettuce, apples, blueberries7
PhytosterolsPlant seeds such as sunflower seeds, sesame or pumpkin seeds, nuts such as almonds, cashew nuts or peanuts, pulses8
Phytoestrogens9, for example Isoflavones LignansSoya beans and soya products such as tofu or soya milk Linseed, pumpkin seeds, whole grain cereals, beans, asparagus, broccoli
SulphidesOnions, chives, shallots, garlic, leeks, cabbages10
SaponinsPulses, soya, green beans, spinach, asparagus, oats11

Note: The substances lycopene, beta-carotinoid, anthocyanins, flavonols, quercetin, isoflavones and lignans are considered subgroups of the respective secondary plant metabolites.

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