The 12 most important secondary plant substances

Secondary plant substances (also called phytochemicals or phytonutrients) are bioactive, non-essential substances produced by plants as defense mechanisms against predators, UV radiation, and disease. In humans, they exert numerous protective effects , particularly with regard to oxidative stress , inflammatory processes , cardiovascular disease , cancer prevention , and strengthening the immune system .

Numerous epidemiological studies and intervention analyses indicate that a high consumption of plant-based foods is associated with a significantly reduced risk of developing chronic diseases, an effect that is largely due to phytonutrients in addition to fiber, vitamins and minerals.

1. Flavonoids

Function and effect:

Antioxidant : Neutralizes free radicals, protects cell structures (DNA, proteins, lipids)

Anti-inflammatory : Modulation of pro-inflammatory cytokines

Vascular health : improvement of endothelial function, reduction of blood pressure

Clinical evidence:
Meta-analyses show an inverse association between flavonoid intake and cardiovascular disease and stroke risk.

Natural sources:

Fruit : berries, apples, grapes, citrus fruits

Vegetables : onions, broccoli

Drinks : Green and black tea, cocoa, red wine

2. Carotenoids

Function and effect:

Provitamin A (β-carotene): essential for vision, skin, immunity

Protection against age-related macular degeneration (lutein, zeaxanthin)

Anticarcinogenic effect (lycopene)

Clinical evidence:
High intake is associated with a lower risk of certain cancers and age-related eye diseases.

Natural sources:
Carrots, sweet potatoes, tomatoes, kale, spinach, pumpkin

3. Polyphenols

Function and effect:

Protection against atherosclerosis and high blood pressure

Glucose metabolism regulation (preventive against type 2 diabetes)

DNA protection through antioxidant effects

Evidenced by:
Studies on the Mediterranean diet show an improvement in insulin sensitivity and inflammatory markers with high polyphenol intake.

Sources:
Berries, pomegranates, walnuts, green tea, dark chocolate, red wine

4. Glucosinolate

Function and effect:

Detoxification of carcinogenic substances via phase II enzymes

Hormone regulation via breakdown products such as indole-3-carbinol

Clinical data:
Sulforaphane from broccoli shows in vitro and in vivo preventive effects on prostate, breast and colon carcinomas.

Sources:
Cruciferous vegetables: broccoli, Brussels sprouts, arugula, cauliflower, kohlrabi

5. Saponins

Function and effect:

Inhibition of cholesterol absorption

Antimicrobial and immunomodulatory effects

Promotes apoptosis in cancer cells (preclinical)

Sources:
Lentils, chickpeas, soybeans, quinoa, oats

6. Phytoestrogens

Function and effect:

Hormone-like, agonistic/antagonistic at estrogen receptors

Protection against hormone-dependent tumors

Improvement of bone density in pre- and postmenopause

Sources:
Soy, flaxseed, chickpeas, sesame, rye

7. Tannins

Function and effect:

Antioxidant, antibacterial

Protection against infections and cardiovascular diseases

Sources:
Black tea, red wine, grapes, walnuts, pomegranate

8. Anthocyanins

Function and effect:

Blood pressure lowering, vascular protective

Protection against diabetic retinopathy

Preventive effects in neurodegenerative diseases

Sources:
Dark berries (blueberries, blackberries), cherries, red cabbage

9. Terpenes

Function and effect:

Anti-inflammatory, cell-protective

Supports the body's own detox enzymes

Antiviral and antibacterial activity

Sources:
Citrus peel, rosemary, thyme, mint, lavender

10. Phytosterols

Function and effect:

Cholesterol-lowering by competitive inhibition of intestinal absorption

Reduced LDL levels demonstrated in randomized trials

Sources:
Vegetable oils (corn, rapeseed, soybean oil), nuts, sesame, sunflower seeds

11. Allicin

Function and effect:

Strong antimicrobial (bacteria, viruses, fungi)

Lipid-lowering, anticoagulant

Blood pressure lowering

Sources:
Freshly chopped garlic, shallots, onions, wild garlic

12. Capsaicin

Function and effect:

Promotes thermogenesis

Pain-relieving when applied topically (substance P modulation)

Potentially anticarcinogenic by influencing cellular signaling pathways

Sources:
Chili, pepperoni, paprika


Conclusion and recommendations for practice

A plant-based, colorful, and diverse diet is key to consuming secondary plant substances. Especially in childhood, this can not only strengthen the immune system but also establish preventive protective mechanisms early on, reducing the long-term risk of lifestyle diseases.

For daycare nutrition this means:

Different colored vegetables and fruits every day (at least 3 colors per day)

Regular use of herbs and spices (e.g. garlic, turmeric, mint)

Whole grain products , legumes and nuts/seeds in varying forms

Gentle preparation (steaming, stewing) to preserve the heat-sensitive phytochemicals

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